# My "New" Lathe



## JohnW (May 11, 2016)

I posted the beginning of this story a couple of weeks, ago, but the posting disappeared, so I'll try it again.

The project started a few months ago, so I'll start with a few postings of history before I get into more recent work I've been doing. I have been taking a bunch of pictures along the way, so there will be pictures.

Back in December we were looking for a metal lathe for Protospace. where I am a member. We came across someone who was selling a bunch of gear and long story short, he had a 16x60 sized lathe (7.5HP), a large Bridgeport clone type of mill (5HP, 48" wide table with a power feed) a smaller 14x40 sized lathe (a 5HP Colchester clone), and a big metal band-saw for sale. He had purchased the gear from an auction several years ago and it spend the time in one of his heated garages having never been used.

He was keen to sell it all for a good price, and Protospace was looking for the lathe and a manual mill.  We found someone who wanted the big metal band-saw, and I was kind of interested in upgrading my current lathe (a 12x36 2HP unit from House of Tools about 10 years ago).

So we made the deal and headed out with a picker truck for the Protospace gear, and I took my Jeep and one of my trailers to bring home my new toy.





So here we are about 15km east of the city back in December. My new toy is connected to the crane and he is about to put it onto my trailer where I am standing arranging some pieces of scrap plywood to place it on. My trailer can handle the weight as long as it is not too much of a point load. It was probably about 3,000lbs once I removed the chuck, cross-slide vice and tailstock. I originally built the trailer as a snowmobile trailer with a relatively light weight deck, so a bit of re-enforcement seemed like a good idea. The trailer has brakes and a relatively heavy axle and springs since I like the idea of having brakes when hauling stuff on BC highways in the winter.

The other lathe that went to Protospace is sitting there beside my unit. It was loaded onto the truck along with the mill  (not visible here), and the big band-saw.


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## JohnW (May 11, 2016)

It was pretty late and dark by the time I got home. As you can see in the last picture the sun was almost setting while we were loading it up. We first had to unload the other equipment at Protospace in the NE, and I live a few km SW of the City, so I just parked it on the driveway when I got home.

Here is what I found waiting for me on the driveway in the morning:






 and from the other end. . . .






The pallet jack was just along for the ride as we were using it move the other gear around at Protospace.


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## JohnW (May 11, 2016)

Here's a closer look at the control panel:






The machine is a made in Taiwan clone of the English Colchester Triumph lathe. As near as I can tell it was made in about 1978 (that is the date on the motor label). It has a 5HP 3-phase 208V motor, and appeared to be in pretty good shape. It was well used and there were lots of chips sitting in semi-congealed oil under the gear boxes and all over the motor, so it was going to need some cleaning for sure.

I did find a few issues along the way, and the postings to follow will show the issues and what I did to fix them.


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## JohnW (May 11, 2016)

The first task was to get this beast off of the trailer. Getting it on was easy; the picker truck did that. I did have a plan to get it off though.

I live on an acreage a few km SW of Calgary that we moved into a few years ago. It included a nice heated shop (3 1/2-ish car garage sized) that I was really looking forward to. The shop only has an 8 foot ceiling, and had a wall down the middle since the previous owner only heated half of it. I had plans for that. I removed the dividing wall and finished and insulated the unfinished half. As part of that project I wanted to have a hoist in the ceiling.

Before I covered in the ceiling, I beefed up a couple of the roof trusses and framed in a big "slot" in the ceiling where I installed an I-beam with a dolly and chain block. The most I had lifted on this since I installed it was my motorcycle. It is much easier to work on when it is lifted up and in no danger of falling over. But that was in the 600lb range, so it was a no brainer. The lathe is 3000lbs-ish so it will be the first real test.

That hoist was how I was going to get the new lathe off the trailer. I backed the trailer in, and hooked the lathe  up to the 2-ton chain hoist I had.

Lifting the lathe would be the real test of my engineering. I connected it up and lifted it an inch off the trailer. The roof trusses didn't make any creaking sounds or come crashing down on me, so I guess my re-enforced trusses were up to the task. Even a bit of bouncing on the lathe didn't bring everything crashing down, so I drove the trailer out and carefully let the lathe down to the ground.

Here is the lathe just before I started to let it down.






There is a 6" I-beam and a chain block in the slot in the ceiling. It didn't fall and crush me, so I was ready to start really checking out the new machine.


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## JohnW (May 12, 2016)

I'll just make one more quick historical post before I move on to the restoration of the machine.

This is what the machine looked like when I first saw it. Actually this was after about 10 minutes of moving piles of stuff and boxes that were stored in front of and on top of it. There are still a couple of tires there that weren't moved until much later.






As you can see it has a taper attachment. Actually not all of the attachment was there, but the most important part was: the taper slides. I will need to make a bracket to attach the cross slide to the taper attachment and a clamp to clamp the stationary portion to fit to the ways if I ever want to use it. Those are relatively easy to make, and I will probably do so some day.

The chuck is an 8" Bison 3-jaw that is in very nice shape with removable jaws. It seems to be in way too nice a condition to be the original chuck. There were two sets of slightly customized soft jaws for the chuck that will probably come in useful some day. The chuck mount is a D1-5, (it uses six 3/4" pins) which is pretty standard, but not really very common.

It didn't come with a 4-jaw chuck. It has a 40 position tool post, but no tool holders. There is some plumbing and wiring for a coolant system, and a coolant reservoir in the right hand base unit, but there was no coolant pump installed.

The inside of the tailstock is a 3MT taper. It is a bit scored inside, so it will requires a bit of work.

What looks like a bit of rust is actually either paint chipped off showing primer, or old dried oil.

It can do most thread sizes in metric and imperial without modifying external change gears, but needs one external change gear changed to do some larger worm gear cuts. It didn't come with that gear. Maybe I'll make one some day if I ever need to make large worm gears.

The chip tray is large drawer that can slide out for cleaning.

Anyway, that is what I am starting this project off with.


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## PeterT (May 12, 2016)

Wow. Congrats on the move & new addition. That's a big boy machine. I'll be interested to see your TLC process.

A while back I was exchanging posts on taper attachments. I'll be keen to see your findings & I hope all your parts are there. I now regret not having selected that feature up-front because a retrofit is not cheap or slam dunk simple. The slider block assembly / mounting is one chunk of it, the other is the lead screw itself. Eventually I figured out lathes accomplish taper/non-taper action differently, but typically have some form of telescoping lead screw on the Y-axis. Good luck & keep up the progress pics.


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## JohnW (May 12, 2016)

Unfortunately I only got the slider block assembly. It looked pretty bad in that it was all brown and wouldn't move so I was scared it was rusted up. Once I soaked it in the parts washer and got it disassembled, all of the brown stuff came off, so it was just old congealed oil. Once I reassembled it, it was actually quite amazing. It has no noticeable play, but slides almost effortlessly. It is difficult to pick up since if you don't hold it level one of the parts starts sliding and tries to knock your hands off.

Peter, you are correct: to mount it properly, the screw in the cross slide should be converted to a telescoping unit and then the cross slide action will always be against the taper attachment. Since I really don't think I will use it much anyway, I will likely just make up a bracket from the back of the cross slide to the top of the taper attachment. If I then take out the bolt that attaches the cross slide to the nut that is on the screw shaft, the cross slide will move with the taper attachment. The compound can then be set parallel with the cross slide and can then be used to adjust the cut appropriately. I will also need to make a bracket that attaches the centre of the slider block to one of the ways on the bed. That is a pretty easy thing to make as well.

That is my plan for now. Maybe I'll get really keen some day and figure out something better if I actually use the taper attachment. For now I'm going to get it all operational without worrying about the taper attachment. A proper job on the taper attachment may happen some winter when I'm bored.

Over the winter the lathe has received a lot of TLC - pictures are coming. After looking at it a bunch, I decided that I really don't want an old beat up dirty lathe, so I embarked on a complete disassembly, cleaning and re-building process. I got yelled at several times for smelling like solvent and was not allowed back into the house unless my clothes went directly to the washing machine and me directly to the shower.


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## JohnW (May 12, 2016)

Once I got the machine inside and warmed up, I started into checking stuff out, disassembling, cleaning  and fixing up worn and broken stuff.






Here is what it looked like under the cover on the side of the headstock. Lots of dirt and old chips. Even the motor that you can see down below is covered in chips and oil.

Some the insulation on the wiring was cracked and starting to fall off from age and exposure to oil. That's not an issue since it will all be re-wired to support the VFD I will be using to drive the 3 phase motor. My shop has a 100A service (sort of) but it is single phase. I say sort-of since my property is fed by a single transformer that is only 90A and that has to be shared with the house. Still, there is lots of power in the shop.

The oily rags are there because it made a big mess when I drained the oil from the headstock and gear box.

The brake mechanism was soaked in oil because the seal on the input shaft was leaking a bit. The brake shoes are somewhat worn, and a previous owner had tried to fix that by extending the yellow bar that applies the shoes, but although that probably worked for a while, it could not really spread the shoes enough without some clearance issues in the mechanism.






You can see here where the brake level has been hitting the brass spacer ring and how everything is covered in oil.

The brake shoes are probably available. I cross referenced the part number cast into them, and it looks like they are common with the front wheel of a 125cc Yamaha motorcycle. I decided there is probably still enough pad there to last my lifetime, so I went with a modification to open the shoes up a bit:






I added a short piece of brass tubing on the top post, and made up an aluminum spacer for the actuating cam.  I spent a couple of weeks wrapping the shoes in an acetone soaked rag and storing it in a plastic bag for a week while I worked on other stuff. Every time the rag absorbed some of the oils from the shoe material until the shoes lost their dark brown color and looked a lot more like a brake shoe.


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## PeterT (May 12, 2016)

So THATS what a brake looks like under the hood. I've always wondered!

I think the teardown & solvent spa treatment will yield nice end results.

Re the VFD conversion, are you saying the box will drive the existing motor, or you replace motor to something that matches the VFD?

What size is your I-beam that obviously held a 3000# lathe? That's impressive. I always thought those had to be supported by heavy duty columns on either end. Look like yours is integrated into the truss system if I understand, its axis is perpendicular to the garage door? 
_Before I covered in the ceiling, I beefed up a couple of the roof trusses and framed in a big "slot" in the ceiling where I installed an I-beam with a dolly and chain block. The most I had lifted on this since I installed it was my motorcycle. It is much easier to work on when it is lifted up and in no danger of falling over. But that was in the 600lb range, so it was a no brainer. The lathe is 3000lbs-ish so it will be the first real test._​


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## Louis Dusablon (May 12, 2016)

Hi Peter

Nice lathe,  I have been restoring mine as well you can check out Old Lathe Project,  It is a 5 hp,  220 three phase machine I did install the VFD and able to use all original dashboard, I did add the variable speed dial.  if you require any info or help let me know glad to help.


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## JohnW (May 13, 2016)

The brake drum is the inside of the triple pulley that is driven by the motor. The pulley is obviously removed at this point. I've seen some lathes that use an external strap on a drum for a brake, but this seems like a good idea where you just use an existing motorcycle part.

As for the VFD, I will be using the existing motor. This picture was taken before I cleaned it all up. there is no really direct way for chips to fall in there, but lots of them made it down there.




I've obtained an Allen Bradley VFD that is rated for a 5HP motor. The VFD is designed for a 3-ph input, but that doesn't really matter since the first thing the VFD does is rectify the input current to feed the internal DC bus. I will need to de-rate the VFD somewhat, which means that it is really just big enough. It is rated for a maximum  22A output, and the motor is rated to draw 14A.  It may be necessary to use a bit of a conservative acceleration curve for the motor to make sure I don't over stress the VFD. In the end, the motor will only draw that kind of current under very heavy loads, which I am unlikely to subject it to, and while accelerating, which can be mitigated via the acceleration curve. Even if I only had 3-4HP available, it would be plenty for my purposes.

Almost all of the control wiring will be replaced (i.e. fwd/rev switches, jog, brake, etc.), since it now only 10V low current instead of the 120V it was previously.

I have also sourced a couple of big 100-ohm 225W resistors to use as braking resistors so I can use the VFD to quickly stop the motor as well. The use of dynamic braking will also reduce the wear and tear on the physical brake.

All that stuff is only sort-of designed in my head so far. I'll post more on my design once it is getting closer to reality.

The ceiling I-beam is 6" high and probably 2.5-3" wide. It is installed parallel to the existing trusses. That allowed me to install it about 18" higher than the ceiling so I gained enough height that once the trolley and a chain block is installed, it can still lift just about right up to ceiling height. The total span is 22 feet from the front to the rear of the shop.

If I remember correctly,  I welded metal straps (1" x 1/8") onto the top of the beam about every 1.5 or 2 feet. I strengthened the existing trusses on each side of the beam by screwing 5/8" fir plywood to the trusses going up 24" or so, and I added a flat 2x6 to the existing 2x4 members of each truss in what seemed like the appropriate places, including along the full length of the lower member, and used lots of #12 screws to put it all together. Then, the straps from the beam connect to a 2x10 that runs parallel to the beam right above it. The 2x10 sits on 4x4's that are spaced every 1.5 or 2 feet that span across 4 of the existing trusses. On top of all that, the ceiling is covered with 7/16" OSB instead of the usual drywall (using lots of screws near the beam), so it provides a lot more strength than the drywall would. I also screwed 12" squares or triangles of 5/8" plywood over most of the joints in the trusses on each side of the beam to be sure there was enough strength there. I hope that makes sense.

I pretty much just kept building until I figured it was way more than enough. I don't think I have any pictures of the structure, or I would post it. It is too late now, since after it was all done I blew in R40+ of insulation that pretty much obscures all of the structure.


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## JohnW (May 13, 2016)

Its easy to post lots of stuff when I'm catching up on a project I've been working on for the last few months. . . .so here is another:

I took lid off the headstock to inspect in there after I'd drained the oil. Here is what it looks like:






Full disclosure: This picture was actually taken after it was all put back together, but I didn't have a good image from when I was taking it apart.

It all looked pretty nice in there. There was just a bit of dirt and some very small debris that had settled to the bottom of the oil.

Once I started checking out all the gears, I discovered that one of the gears on the input shaft was spinning on the shaft. All of the gears on the input shaft are locked into place with a long key - or at least they should be. In the picture above, the input shaft is connected to the triple pulley (the brake is inside that pulley). The rest of the shaft and its gears are sort of visible under the secondary shaft at the bottom of the picture.

Power goes from the input shaft up to the secondary shaft when one of the four gear sets is engaged (four main spindle speeds), and then over to the spindle shaft via the two sets of gears at the left side of the spindle (spindle high-low range). These gears are shifted via the concentric levers on the front panel (there is a picture of that way back near the beginning).

At that point the pulley and brake had already been removed, so with the removal of a few snap rings, the input shaft should have pulled out reasonably easily. Well, it didn't. I had to weld up a custom puller to pull the input shaft off of the input gears and out of the right side of the case. Every millimeter had to be pulled, with me changing sets of washers and spacers on my homemade puller thingie every couple of inches.

Here is what I found:






At some point in its life, the spindle must have had a serious crash. It sheared the keyway in half, leaving half of the keyway in the slot in the gear, and the rest in the shaft. After that, the gear could spin relatively freely on the shaft.

In the end, this looks much worse than it was. The shaft is scored up a bit under the one gear, but once I filed and polished the high spots back down, the gears still fit it very nicely. The gear that spun, was obviously hardened as it only had some very minor marks on the inside of its centre hole. A bit of grinding compound on a slightly under sized bit of steel I machined up cleaned that right up. Since the gears are fixed to the shaft I didn't think the shaft would need to be replaced.

Since the keyway slot was widened out, I put the shaft on my mill and extended the slot all the way to the end of the shaft. That gave the gear that spun a nice clean slot to hold the keyway a bit better. I bought a new 6mm keyway, then cut it to size to replace the whole key. It was way too tight, so I needed to spend a few hours polishing down the keyway by about 0.03mm to get a good fit.

Unfortunately I didn't take a picture of the repaired shaft, but it went together reasonably smoothly (I used a new oil seal to keep the oil off the brake shoes), and the input shaft was fixed.

Overall, a pretty easy and cheap fix ($10 for the keyway, $2.50 for the seal, and several hours of work) for what could have been a really serious problem.

While I was in there, I carefully inspected all the teeth on all the gears and everything was fine. I also documented all the gear ratios for future reference, including the high-low and reversing gears for the feed drive output shaft.

Here is what the headstock looked like with the input shaft and one of the shifter shafts removed:






That all went back together nicely. I looked up what oils was required, and it seems that hydraulic oil is a pretty standard lubricant for lathe headstocks, so I added the 8 liters or so that it took to fill it and bolted the lid back on. Actually that's a lie since I didn't really bolt the lid back on until I had finished cleaning and painting everything, but that comes later in the chronology.

Since it made a big mess when I originally drained the oil, I replaced the original threaded oil plug with a short pipe nipple and a cap, so it is possible to drain the oil into a funnel and catch it before it runs all over everything. Hopefully I will never need to drain the headstock again, but it will be easier in the future if I have to.


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## JohnW (May 14, 2016)

One note: These postings are not really chronological at this point since I did a lot of this work over the winter. I think it makes a bit more sense to combine all the work on one part of the machine into a single posting at this point. The current status of the project is that is is mostly re-assembled. I did a final degreasing and painted the back splash today and will give it another coat of paint tomorrow. While it dries, I can work on installing a DRO I have for the lathe, and then the final wiring will be the last major bit to work on. It will start looking pretty complete once I install the back splash, but it is easier to work on without that in place. Since the machine will be hard to move once it is fully assembled, I am doing the assembly with it about 2 feet from the wall where it will live. Then I only need to move it back 2 feet to its final resting spot.





Above you can see the mainly assembled, cleaned, painted lathe as of this afternoon. In the foreground, I've just painted the back splash.

The next thing I worked on was the carriage assembly and the feed shaft and lead screw. First, I took it all apart and cleaned all the gunk off of everything. Here is the cleaned and re-assembled carriage gear box looking up from the bottom:





The bottom cover had a homemade gasket on it that did not fit very well. The bottom cover was really just a piece of 1/4" hot rolled that looked like it had been plasma cut and ground a bit on the edges to make it look a little bit better. Rather than make a new gasket, I hammered on the plate a bit to get it as flat as I could (it was pretty good), then put it on the mill and machined a nice flat and smooth sealing surface. When it goes together I will just use some silicone on the mating surfaces.

I disassembled, cleaned and reassembled most of the carriage. A common problem I've come across on this machine is that there is 30+ year old semi-dried oil in many of the parts. All of the moveable dials on the hand wheels were almost impossible to move. Most were even really hard to get apart. Once they were cleaned and re-lubed they were nice and smooth. There wasn't a real problem or even any corrosion, just dried up oil gumming up all the works. All of the hand wheels have nice ball-bearing thrust washers, but again they were generally all gummed up and worked beautifully once I cleaned them.

While it is apart I again counted all the gear teeth and documented that. Why? Once I'm done I will be able to make up my own accurate feed and threading tables. The ones on the faceplate have at least one error and make some approximations. I'll have a posting on that later.

The more astute will have noticed that there are some missing parts in this picture. In particular one gear and the shaft and gear that drives the feed against the gear rack under the ways is missing. That is because in removing the carriage I found the worst problem that the machine had. Here is the feed drive shaft from the carriage.






And another view of the gear itself:






One tooth was broken and the one beside it is badly worn and / or bent. The carriage still moved OK when using the hand wheel, but did have a bit of a rough spot when the missing tooth was run over the rack. It didn't skip yet, but would do that some day. Clearly this is not the way I wanted to put it back together.

I've read about cutting gears and the various standards involved, but now it was time to do lots of Goggling and bone up on the subject.

With some careful measuring, I determined that almost all the gears on the machine are metric Module 2. That includes the feed drive gear above and the rack under the ways. M2 is a standard metric gear size, and basically means that each tooth is nominally 2 x Pi millimetres apart - i.e. 6.28mm.

To repair this I will have to fill the missing tooth with weld, and machine it down. I thought about using a hand ground custom HSS cutter, but I've always wanted to play with making gears, so off to China I went (by e-bay), For about $100 cdn I ordered a set of eight M2 gear cutters. The gear cutters needed a 22mm arbour, which, of course, I didn't have, so another e-bay purchase out of Hong Kong had a 22mm R8  arbour on its way (via slow boat from China).

So, fast-forward about 7 weeks and the gear cutters and arbour arrived. The gear cutter package fell open in the mail and two of the cutters fell out! The good news is that the cutter I needed (for 12-13 tooth gears) was there. The seller promised to send me the missing two cutters, and I am still waiting for that (it has only been about 4-weeks so I'm not worried yet).

I'll cover the gear restoration in the next posting.


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## JohnW (May 14, 2016)

So finally some good machining content in this post . . .

I researched gear repair and came to the conclusion that filling the gears in with silicon-bronze via a TIG brazing process would be the best idea:

Brazing does not need nearly as much heat, so there is less chance of the heat warping the shaft.
Silicon-bronze is quite strong and hard. The bronze also has nice lubrication properties against the steel rack it be meshing with.
For non-critical gears, SiB seems to be the preferred filer material for gear repair - especially for cast gears. This is not cast - it is probably 1018 or something similar. SiB is not what you want to repair a differential pinion gear with, but for stuff like this it should be fine.
I'm not that good a TIG welder (yet), so using SiB brazing reduces the chance I will ruin the shaft while attempting to weld it.
I started out by trying bronze fill on a chunk of rebar, and machining it down to see if I can get a nice fill and good adhesion. I thought the rebar is usually pretty terrible metal and if I could work with it, I'd do OK with the gear. After a couple of practice runs on rebar and cutting it away with the lathe, I was having good success, so I started with the real gear.

First, I ground out the broken tooth, and removed most of the bent / worn one:






I filled it with SiB and let it cool relatively slowly so it would not get hardened.






Another view:






Then I put it on the lathe and got rid of all of the extra material. That identified the areas where I needed some more material, so I added more, and again let it cool slowly.






Another pass though the lathe (I'm using my old 12x36 for all of this) and it looked good:
















In the next post I move over to the mill with the rotary table and involute gear cutter.


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## John Conroy (May 14, 2016)

Very nice work John. Looks like that gear repair is going well. It's going to be a really nice lathe when you are done.


John


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## JohnW (May 14, 2016)

And now to cut the teeth . . . .






I installed a huge number of fluorescent lights in my shop and the mill is right in front of a window, but it seems there is still not enough light for my old eyes.





I mounted up my 6" rotary table and the new arbour and involute gear cutter on my mill. I have a 4-jaw chuck I can mount on the rotary table, so it took me a bit of time with a dial gauge to get the gear shaft centred to 0.002" or so. I couldn't get it any better. I think that's as good as the rotary table holds the chuck in position, but it should be good enough for this project.






I carefully lined up to an existing gear tooth (using a magnifier) and noted the angle being indicated by the rotary table. I would need to move it 13/360 degrees for each tooth which is 27.6923 degrees, or 27 degrees, 41.5 minutes (the table is calibrated in degrees, minutes, seconds).

It was time to go into the house and make up a spreadsheet that calculated the absolute positions for each gear for me, since I was way too likely to make a mistake trying to change positions. I set up the spreadsheet such that I could enter the starting position and it would calculate the absolute position of each tooth-gap for me.






The 0-30 ticks column is there since for some reason my rotary table has the "minute" ticks listed as 0-30 instead of 0-60 on the dial. With that column I can just read off something like 154-4 to set it for tooth number 6. The rotary table has a 90:1 ratio, so it moves 4 degrees for each rotation of the hand wheel and in theory can position to about 2 minutes of angle.

When I went through a few teeth manually, the cutter just barely scratched the metal (I tried it on about half of the existing teeth), so it looked like it was all setup properly. Sorry there are no pictures of the actual machining, as I was busy keeping my head straight on what I was doing.

The SiB is pretty hard and my little mill was vibrating a bunch while it was cutting (I had all but the X direction on the table locked down while cutting). Apparently SiB can be hard on HSS cutters, but the cheap Chinese cutter survived and still appears to be sharp.

I did it as two main passes. The first I did slowly and cut almost to depth (maybe .010" short). The second pass was to depth, with a couple of clean-up passes.

Here are the results:






I'm pretty happy with it. There is one side of the tip of one tooth on the right hand side of the repaired teeth that is missing just a bit of fill right on its edge, but that is more cosmetic than anything since that portion of the gear does not actually mesh with the rack. I let the fill material extend just a little bit past the original gear to add a bit of strength to the teeth since there was clearance, and that is where most of the bad tooth is. If anything my repaired teeth look less worn than the originals.

Reassembling the carriage and installing it was uneventful, but the end result is that the carriage now advances very smoothly as it should. Once it is all assembled, you can't see this gear anyway.

Clearly the feed was crashed pretty badly in the past to rip off that tooth. The feed gearbox output shaft used a steel roll pin (hardened!)  as the drive mechanism to the feed shaft that goes along the ways. My other lathe originally used a brass pin there. I crashed the carriage once and it sheared off the brass pin on that lathe with no other damage. I didn't have any brass around at the time, so I made a replacement pin out of aluminium which has worked well for the last few years.

Aluminium is softer than brass, so it should shear more easily. I did the same thing when assembling the feed and leadscrew shafts on this lathe - I used aluminium shear pins on both shafts to protect the gears. I don't know if the original lathe used steel pins or they were replaced by a previous owner, but the aluminium just seems like a way better idea to me. As long as it doesn't shear under normal use I think it is the right thing to do. If it wears out every 10 years or so, I can deal with replacing it.


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## John Conroy (May 14, 2016)

Great job John, that should last the life of the machine.

John


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## JohnW (May 14, 2016)

Thanks. Or at least my lifetime. The machine is already older than I have left!


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## PeterT (May 14, 2016)

Great pics & learnings here. I am really impressed by your effort. Especially the gear fix. I'm going to guess that the drive shaft is hardened? (ie.  turning off the remaining teeth & retrofitting a commercial module gear on the reduced boss was probably never an option?). I've read some articles where people heat (anneal) things like this in order to modify fix, but I've never really been clear if they leave it that way or re-harden & then risk distortion.

It sure paid to look under the hood to detect the crash carnage & deal with it now. If you have the mindset & resources to put TLC back into the machine you are going to get something like new, or in your case, probably better than new. This supports my personal theory: if I ever buy a retro project lathe, I better keep my existing lathe & mill, Ha-ha.

Are you going to DRO this baby & if so, what system are you looking at?


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## JohnW (May 15, 2016)

My current lathe and mill were purchased new about 7-8 years ago, so I knew their condition. With this lathe I quickly decided that although I wanted a larger lathe, I didn't want a beater, and I've just got sucked into the TLC vortex. I'm having fun though, and it is cheap entertainment in the end.

I don't think the shaft was hardened. I don't think I heated it up enough to anneal it (the SiB melts at well under 2000F, while steel needs closer to 3000F). The shaft near the teeth was certainly not hard when I was cutting the teeth as I ended up cutting slightly larger notches into the shaft when I went to the end of tooth. It was also easy to grind off the bad teeth - and that was before I heated it at all.

Once you have a lathe and a mill in the shop you never want to be without one, especially when you are working on stuff like a lathe or mill. My old lathe will go up for sale eventually, but not until the replacement is completely operational.

I never thought about cutting the shaft down and then adding a commercial gear via a press fit. That would certainly have worked, but where is the fun in that? It would probably have been my third alternative. I would more likely have pressed on a blank and then cut the teeth if the brazing had not worked out. I also thought about making up a whole new shaft. It doesn't have any splines or even a keyway in it, so it would not have been too hard to make. 

In the end I was probably somewhat blinded by an inherent desire to make a gear some day, so this was my starting point. I mentioned that most gears in the machine are M2, which encouraged me to buy a full set of cutters. If any gear ever fails, M2 cutters are what I will need to fix it. Also if you look waaaay back somewhere up there, I think I said that there is a 48 tooth external gear missing for the feed section of the lathe. That replaces the 24 tooth gear on the output shaft of the headstock. It is not required unless I want to cut stuff with a pitch over about a quarter inch. The normal gearbox can do everything from about 84 TPI through 4 TPI (0.25 mm through 7.0 mm). The 48 tooth external gear extends that to 2 TPI or about M14 which are pretty big and rare threads to need. These are things I'm unlikely to do, but being just a bit anal about stuff, I will probably want to have that gear just because some day. It is better to have a tool you don't need, than need a tool you don't have!

Part of the reason I went with repairing the gear is I've never done that before. Deep down my biggest hobby is learning stuff, so I could not pass up the opportunity to try something new.

The lathe is indeed getting a DRO. I got DRO's for both my mill and lathe about 4 years ago (it was an Xmas present), and installed it on the mill, where I will never want to be without one again. I never quite got around to installing the DRO on the lathe (the timing was just wrong as other life projects got in the way for a couple of years).

I got my DRO's from Shooting Star Technologies (http://www.star-techno.com/index.htm). They are a BC based company that makes DRO's based on a precision rod with gear teeth cut into it. On my mill it seems to be reliable and repeatable to 0.001", so I am happy with the unit on the mill. I spent part of this afternoon installing the DRO on the "new" lathe. I might get it finished tomorrow. I will eventually post photos.


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## JohnW (May 15, 2016)

Here is another minor issue and the fix my lathe got a couple of weeks ago:





The curved t-nuts that hold the vice to the cross slide were both cracked and a bit bent from over-tightening over the years. Here are the old nuts on top of a piece of hot rolled scrap that has already been through the mill to square it up and remove the scale.






I drilled and threaded the two holes first, then bolted it from the bottom with countersunk heads into to a sacrificial piece of MDF that I bolted to my rotary table at exactly the radius of the circular vice hold down slots in the cross slide. This lathe has a strange mixture of metric and SAE fasteners. The vice t-nuts are 3/8-16. There are lots of 1/4-20's holding on access panels yet most of the other bolts are 5mm, 6mm and 8mm.

Once I had it carefully mounted in position it was just a matter of taking a bunch of small passes with an end-mill while rotating the table to hew out one large curved t-nut. I had a lot of vibration from the MDF flexing. I should have used 3/4" instead of 1/2", but that is what I had lying around. Still, it worked OK by keeping the cutting passes less than about 0.020" of Z motion.

This time I remembered to grab the camera in the middle of the machining operation. This is when the narrow part of the nuts have been cut. I then moved the table in the X direction and cut the curves for the shoulders of the nuts. Since it was mounted on MDF, I just cut right into the MDF to finish the sides.






I cut the piece in half and got two nicely fitting curved t-nuts. The nuts sit about 0.020" below the surface when they are pulled up so they will allow the vice to be clamped down nicely. They are a bit longer than the originals, and are as long as they can be and still fit through the slot in the bottom that they must be inserted through.






Here is a comparison of the old and new parts:





The originals used bolts that threaded into the t-nuts. I think that contributed to the failure since it eventually wore out the threads, and forced the bolt to hold in the top, very thin portion of the nut.

Instead, I made a couple of studs out of two grade five 3/8" bolts with rolled threads. I have lots of 3/8" ready rod around, but I do not think they are made of very strong metal. I had to extend the threads on the bolts a bit to make the studs - you can see where that started since the bolt is a little bit small right at the end of the rolled threads and leaves a short bit of missing thread on the stud.

I put the studs into the t-nuts and glued them in place with JB weld while keeping a bit of tension on the studs so they would be metal-to-metal while under tension. That way the rolled threads are sticking up and will see the stress and wear instead of my cut threads, the studs won't loosen, and the JB will add some strength to help stop the nuts from splitting like the previous ones. There is still very little metal on each side the threaded holes near the top.

The chamfered edges of the t-nut shoulders was not intentional. That was just the edge of the original metal. The new nuts still have a longer shoulder than the originals.

I had a couple of nice 3/8" shoulder nuts from a small hold-down kit I have for my rotary table. I'll e-bay some replacements out of China some day, but this was a better use for them for now. The nuts were just a bit too tall to fit properly on the vice, so I did two things there. I milled down the nuts a bit, and I took a 1" end mill and cleaned up the mounting surface on the vice by cutting out 0.040" or so. The vice mounting flange was a bit beat up at the edges of the holes by the small surface area of the original hex head mounting bolts.

The other reason I went with the studs is that I prefer to be able to use a wrench to tighten the vice over using an Allen key. With a nice polished surface on the bottom side of the nuts, and a large smooth surface on the vice mounting flanges, the vice can now be tightened very smoothly without moving while the nuts are turned.

And the final result:


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## PeterT (May 15, 2016)

Its always good to use a 3 foot snipe to really crank down that compound I always say   When I DRO-d my lathe, I also put an encoder on the RHS of compound mine is crowded in there. I ended up having to use cap screws for that reason. My T-slot has a hole on the underside to load the T-nuts in from the underside. I don't quite see how the wider part of your nuts got in there, the threaded boss looks to be the same width as the groove on the base. What am I missing there?

I also put in 2 filler crescent shaped inserts between my T-nuts so they always stay phased at 180-deg if I removed the compound, but this is more to deal my setup being a little more blind finding the nut holes again.


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## JohnW (May 15, 2016)

With the studs sticking out it is easy to move the t-nuts and position the vice onto the studs, so the spacers are not really required in my case. They are a cool idea though.

My curved t-nuts go in from the bottom via a slot that you can't really see in the previous photos.






In this image I was test fitting the nut by inserting it upside down before I cut it up. You can see the opening the t-nuts have to come up through from the bottom in the upper left portion of the slot. I made the new t-nuts as long as I could and still fit though that hole. I don't think it really matters anyway since most of the clamping force will be very close to the stud. I think the longer nut may slide a little more smoothly in the slot.

My lathe DRO is only two-channel, so I will still have to watch the dial and count turns on the compound.


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## Tom Kitta (May 15, 2016)

Quick question about VFD - how does the 5hp VFD work on your lathe - have you tried it yet? I know there is a lot of talk about "some" VFDs having issues with single phase input as they are using 4 out of 6 inputs & there is some talk about de-rating VFDs.... not sure whatever this deals with people simply wanting bigger. 

Other thread talks about 3hp VFD being able to start 50hp motor over 20-30 seconds...

With a lathe it seems the startup is critical as the chuck is heavy - not so with a mill.

Yet other people talk about how it is not possible to run multiple motors on a VFD - while other people compute the VFD power needed just to do that.

Great work on the lathe BTW - I see how much I have to do to restore my old K&T 2E - she is older than my dad. So far the mill head and gears were in as new condition.


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## JohnW (May 20, 2016)

Sorry, not a big update today, as I'm out of town and just wasting some time in a hotel room.

Most of the ball-oilers (oil nipples) on my lathe were either missing, badly damaged, or just plain gummed up. I don't really have any good pictures pictures of the old ones, but here is what I did.

The machine uses 6mm, 1/4" and 8mm oilers. I looked through e-bay and the usual sorts of suppliers and they are available, but for $5 to $6 EACH plus shipping!. I found one guy on e-bay (out of China), who was selling sets of twenty 6mm and 8mm oilers for less than $5 Canadian (including shipping). He didn't have any 1/4" ones listed though.

Wait a few weeks and here is a picture of a few of the 6mm ones that showed up in the mail. The 8mm ones looked similar. They are very nice little units for super cheap.





So, what to do about the 1/4" ones I needed?

I found some thin 6mm OD brass tubing in my collection that could shim them up, so I built a swaging tool to expand the 6mm OD tubing to just less than  6mm ID.

First, I cut the tubing into a few 7mm long pieces.
Then, I tapped the long part of the tapered swaging tool into it using the smallest hole in the die portion (#1).
Then continue with hole #2 which is a little bit bigger.
Then finally with hole #3 the taper would go right through and the ID was just under 6mm with the OD just over 1/4".




The reason for the different sized holes is that they needed to press against the edge of the tubing so I could press the tapered swaging tool through. With too big of a hole, the tubing would just slide into the hole.

Then I pressed a 6mm oilers into the little piece of tubing. The final hole in the die is tapered, so it rivited the brass tubing over the end of the 6mm oiler so it still has a tapered end to make it easy to tap into the 1/4" oiler holes.

Here is what the modified oilers looked like:




And here is what the oil holes look like with the nice shiny new oil nipples in place.




Unless you look really closely, you can't even see the sleeves on the 1/4" oilers.

So, for a $10 investment I have nice new oil nipples and a small bag of extras for another project.


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## Jimbojones (May 20, 2016)

Nice work, John. Glad to see it come together


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## Johnwa (May 20, 2016)

Nice work!  I searched aliexpress for oil nipples and it came up with a bunch of scantily clad females.  I was a little apprehensive searching for ball oilers, but that one worked.


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## JohnW (May 20, 2016)

I guess I should have posted this information before:

If anybody else is looking for these, the e-bay seller I used was: *wenyuandin*
He described them as: *LOT 20 Brass Push Button oiler press fit ball oiler for Hit&Miss Engine Motor*
*





*

Disclosure: I have no connection to the seller other than have made one purchase that I am very satisfied with.


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## Bofobo (May 23, 2016)

JohnW said:


> Its easy to post lots of stuff when I'm catching up on a project I've been working on for the last few months. . . .so here is another:
> 
> I took lid off the headstock to inspect in there after I'd drained the oil. Here is what it looks like:
> 
> ...


I recently experienced a sheared woodruff key in my latest dirtbike acquisition. It was all my own fault for not putting enough torque on the bolt, it began to come loose but would still run untill the key sheared in two  oops but some slight grinding to fit a new one has yielded great results. No tow this muddy weekend! Lol 

Keep this one coming it's looking great!


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## JohnW (May 24, 2016)

Time to catch up on some stuff I did a few months ago - the chip tray and some of the painting.

The original chip tray was a huge drawer that hung under the lathe bed. The best picture I have is one I posted before from when I first saw the lathe before I bought it. The tray is sitting partially pulled out in this image.




 

The tray is probably great if you are doing lots of cutting all day long. It will hold a day's cuttings and let the coolant drain back into the reservoir for re-use. The whole tray then slides out to make it easy to empty. The tray actually sat a little bit crooked as some angle iron had been welded in to give it some additional slope and it did not really slide in and out very well. 

I want to build and install some large drawers under the lathe to store big heavy stuff like the chucks, and did not like the way the drawer worked. Storage space is always at a premium in any shop smaller than a large Walmart store, so I don't like wasting the space under the lathe.

I cut out the front and part of the bottom of the the drawer with my plasma cutter, straightened it and welded it in place with the rest of the sheet metal that sits under the lathe to make up a smaller, flatter tray. I still kept some slope that goes to a drain pipe that feeds into the right hand stand where a future coolant pump may go.

Here is the bottom of the new welded together chip tray:




 
The back of it is facing the camera. I overlapped the metal for a couple of inches and tacked it every inch or so on the bottom. The top was a continuous weld. It slopes to the welded area from the front and the back, and also slopes towards the tube that sticks out on the right side in this picture. That tube goes into a hole I made in the side of the right hand stand, where I will mount the coolant tank and pump if I install one some day. In the meantime, I will just put on a short piece of hose that can drain any cutting oil that runs onto the tray into a small container.

The shiny parts are where I ground the paint off for welding and where it came off because I was pounding on it to straighten out the original bend.

Here it is from the top:




 

I used some body filler to fill in some of the dents and cracks from the original pan (and pretty up a few bits of my ugly welding). The original lathe had body filler all over the place to smooth it out over rough welds and castings. A lot of that came off during pressure washing and especially when I was hammering on the chip pan. Once I sanded the filler, it didn't look nearly as beat up any more.




 
And with some paint it actually looks like it was was meant to be like this. You can see the drain hole on the far side of the lower part of the chip tray. Although the paint looks like it has a lot of brush strokes (it was still wet when i took this picture), as it fully dried and hardened up over a couple of weeks the finish came out looking pretty good. You can see the back-splash and other metal covers leaning against the wall in the background. They haven't been painted yet.


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## JohnW (May 24, 2016)

Another quick post to catch up on some old and new images of the general assembly and painting. . . .

The paint was not in too bad shape when I got the lathe, but by the time I hit it with degreaser and used the pressure washer on it, a lot of paint and filler flaked off, so it really needed to be painted. The insides were only ever painted with a flat primer that was really hard to clean.




 
These are the base castings after cleaning just before they got painted.




 
This is the stripped down lathe after some painting.




 
I panted the bases (inside and out) and re-assembled the main lathe components. This is still being done under the ceiling hoist I have in my shop. 

I used my plasma cutter to cut a new door into the front of the right hand base unit before painting it. It is made of 3/8" steel (not cast). It had an opening on the back, but that would be nearly impossible to get to once the lathe is against the wall. Eventually there will probably be a coolant tank and pump in there. I also welded in a couple of pieces of angle iron to support a base shelf inside the right hand base unit.

I then raised the main assembly onto a heavy duty axle I have (1.5" steel bar with a bearing on each end - visible in this picture) and a heavy duty moving dolly type of platform I have and rolled it over to the other side of the shop and positioned it about 3 feet in front of the wall where it will reside and used a crow bar to let it down onto a couple of 2x4's.

You can also see the 40A 220V stove plug that will power the new beast, and my mill in the background.

Once it is fully assembled (and heavy), I only have to move it back a couple of feet and put it on proper supports.




 

I painted lots of other parts before assembling them.






One corner of the back-splash was cracked, so a bit of MIG welding, grinding and painting fixed that up:




 

And the back-splash with a fresh coat of paint on it with the now more assembled lathe in the background.


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## JohnW (May 30, 2016)

A couple of days ago, I worked on making new rubber "shoes" for the lathe. The lathe has six adjustable levelling screws on the bottom of the bases - four under the headstock, and two under the tail stock section. The bolts have rounded ends, but I think they would put too much of a point load on my shop floor, likely damaging the surface when I turned them to level the lathe. My solution was to make 3" round hard rubber shoes with a steel top so the lathe could still be easily levelled, but still spread the load a bit and provide a bit of vibration damping.

My solution was to use modified hockey pucks. Hockey pucks are cheap, 3" in diameter, and just about the right material for this.

I started off by plasma cutting some 2 1/2 inch disks from some scrap 1/4" steel plate I had. I got all six out of one piece of scrap with almost no waste. I created a 3" diameter template out of a piece of 1/4" acrylic I had by cutting it out on my old lathe. I was a bit aggressive in cutting out the hole and chipped the acrylic a bit, but it still worked fine as a template. It got slightly melted in a couple of spots during the cutting by some wayward plasma, but it held up for the job, and could still do a bunch more if I needed them. I made sure to remove the acrylic as soon as I was finished cutting so it would not get over heated by the metal.





Here is the acrylic guide clamped to the scrap (it had already had a few disks cut out). The plasma cutter cuts about 1/4" inside of the guide disk, so even in this case I ended up with a nice round disk. When you are cutting something like this, make sure to cut off the little corner bits first so the whole piece doesn't drop out with the corner you were about to cut still attached and then you have to try to re-align the template to cut off the last bit. How do I know that?





Here is me doing the plasma cutting.





I did a quick grind along the edges of the disks to clean up the dross from the plasma cuts, and then put them on the lathe with a 3/4" ball nose end mill in the tail stock to make some dimples for the lathe levelling bolts to fit in.





I put the hockey pucks into the lathe and cut out a relief for the steel plates using an HSS bit. The pucks were really hard on the bit! On the third puck I could smell some rubber burning and the HSS bit was completely dull. The edge had been rounded over and made all shiny by the rubber. After that, I re-sharpened it after every two pucks since it would quickly get dull again.





I was aggressive in the cutting and ended up with a big pile of rubber spaghetti, so I was not doing lots of rubbing with the bit. Maybe hockey pucks use silica sand as a filler or something? I never thought the rubber would be so hard on an HSS bit. The huge rats nests of rubber made it hard to see what I was cutting.





I put a dab of silicone seal on the pucks and inserted the steel disk. A squish in the vice spread the silicone enough to come out a bit around the edges.





I've left them sitting in a clamp so the silicone can set. I'll probably leave them there until I'm ready to move the lathe into position and onto its new shiny black shoes. It will probably take a while to cure since it does not get a lot of air under the disk.

A quick update: I mentioned that two of my set of 8 M2 gear cutters got lost in the mail. The Chinese e-bay seller was a good guy and he re-shipped the two missing cutters. They arrived a couple of days ago so it all worked out. You gotta be patient when dealing across the Pacific.


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## Louis Dusablon (May 30, 2016)

I had those under my 14x40 found them a bit bouncy,  made some steel ones with a stick on sandpaper underneath worked great.


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## JohnW (May 30, 2016)

Hmmm, I'll have to see how they work. If they are a problem, I'll just rip off the pucks and go with the steel disks. It will still be a few weeks until I know.

I like the idea of adding on the stick on sandpaper to the metal though.


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## Tom Kitta (May 31, 2016)

Some great ideas!

I also have few oilers I need for my old mill - good find! The hockey puck gave me an idea! Way cheaper then buying commercial stuff - I guess I am going to buy a lot of stuff at sports store for "alternative" uses.


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## John Conroy (Jun 1, 2016)

I've been using hockey pucks under my 2500 lb mill for a year now. I think they work great.

John


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## Louis Dusablon (Jun 1, 2016)

No punt intended here
I do have pucks under my mill also


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## Louis Dusablon (Jun 1, 2016)

they will be replaced either with steel or aluminum disk
just my thought.


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## JohnW (Jul 6, 2016)

I haven't posted an update in a while. Back when the weather was good, I was off riding the motorcycle a lot.

This is another catch-up post showing some work I did earlier this spring.

One of the sub-projects I worked on along the way was the switches driven by the carriage mounted fwd-off-rev level. The lever turns the lowest shaft long the front of the bed, which then moves a rod in and out that goes to the back side of the lathe (lower left in the image below).

The shaft has a keyway along its length, that is engaged by a key in the collar that the fwd-off-rev lever attaches to (a pretty standard configuration). The key was half worn through, so I machined a new key. Sorry no pictures of that. I also squared up the notch that creates the "off" detent position. You can just barely see the notch in the image below.




 

The rod had a couple of hokey levers with a small ramp brazed onto a bolt that actuated two micro-switches as the rod was moved in and out. When I got the machine the tops of the micro-switches were covered with a fine metal-oil mixture, which is interesting since the screw connectors the top of the micro-switches were switching 120V to drive the main motor relays (aka contactors). That was a fire just waiting to happen.

Here is the rod along with the original switch actuator ramps and the new one I machined out of a block of HDPE.




 

Here it is installed with the original (cleaned) micro-switches. I had some nice flexible shielded 8 conductor cable, so I connected up all the contacts. The cable will run back to the electrics box where I can connect up the appropriate contacts and run them back into the VFD. These wires will only be carrying low-current 10V signals.




 

The two ramps slope in opposite directions. It is shown in the off position here. The rod moves in to turn on one switch, and out to turn the other one on.




 

And since some metal filing apparently manage to get down there - it is behind the back splash and reasonably well protected - I installed a plastic cover over it (the bottom of a one litre Castrol oil bottle). Having a shaving fall across a switch contact and turning the motor on unexpectedly would be a BAD thing.






The next topic will be the installation of the DRO, which I started a few weeks ago, I'm going to finish it this evening, since all I have left to do is mount the display unit.


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## JohnW (Jul 6, 2016)

I just came in from the workshop after finishing the DRO install on the lathe.

Here is what it looked like today. It's getting close!






As usual, the story starts a while ago (early May) ago when I started on the DRO install. I bought DRO's for both my lathe and mill about four years ago. I never got around to installing it on the lathe, which turned out to be a good thing so I didn't have to move it over to this machine. Procrastination can be good sometimes.

They are from Shooting Star Technologies (http://www.star-techno.com/), based in BC near Chilliwack. That was nice since the Canadian dollar was low back then so buying a Canadian product made sense. I've been quite happy with the 3-axis unit on my mill. They use a 1/4" steel rod with a precision gear rack machined into it, and a rotary encoder that slides along the shaft.

So here are some pictures of my install. I made up all the aluminium bits you see, including placing all the encoders and rods underneath 1" x 2" x 1/8" aluminium angle's to protect them. The big aluminium bracket holds both encoders and is bolted to the rear of the carriage. The two "unused" bolts are there to bolt on the taper attachment, which will fit with the DRO brackets installed.






If you look really carefully at the lower front of the tailstock (below), you can see a small notch I filed into the angled portion of it. That notch will cleanly hit the aluminium angle protecting the Y-Axis DRO sensor, so when the tailstock hits the carriage no damage should be done. It would still be a bad thing to power feed the carriage into the locked down tailstock!






The notch in the Y-axis cover (below) is there so I can reach the oiling holes for the ways.

I haven't mounted the DRO display yet - just testing it here..






I was pondering how to run the wires from the encoders to the display without having them catch on stuff. Luckily, I was going away on two one week trips to Oregon shortly after this (one by car for business, the other by motorcycle to wear out the sides of my tires). That left time for an e-bay order of some drag chain to arrive from China. I found some for about $6 per meter, so I ordered it and went away while the slow boats crossed the Pacific.

I got it a couple of weeks ago, and installed it last week. While I was at it, I installed a vinyl hose so I can easily run coolant up to the moving carriage in the future. It is easy to install now before installing the chain, and before the back splash is installed.






That just left the display to install. I wasn't really sure where I wanted it, so I made up a swinging bracket that allows the display to move anywhere in an arc about a foot in radius. The wires run through some split loom to protect them. There is a short piece of 12ga solid copper wire in the loom near the right hand side in this image that makes it stand up so the bracket can move without stressing the wire.

The bolts at the swivel points are threaded into the lower brackets and have lock nuts on the bottom. That allowed me to adjust the joints to be just a little bit stiff so it will stay where I move it to. They can easily be readjusted in the future if it loosens up.






Here is what the finished install looks like. The display looks fuzzy because it still has the protective plastic on it.






I've started working on the wiring, and I will probably work on installing the VFD and the various wiring next.


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## Tom O (Jul 10, 2016)

Looking good John your doing a great job!


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## Janger (Mar 20, 2018)

Just great work John - I forgot how detailed this thread was with all the pictures. Very inspiring to add the shooting star DRO I have in the cupboard to my lathe..


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## JohnW (Mar 25, 2018)

Its been a long time since I've posted any progress on this project, although I have actually done some stuff on the project over the last two years. . . .

I've added a coolant pump. Busy Bee had a 220V coolant pump and reservoir on sale about 2 years ago - I think it was significantly less than $200.

https://www.busybeetools.com/products/coolant-pump-for-metal-working-mach-csa-b3087.html

They call it a 5 gallon reservoir, but that is only true in some other reality. Realistically, it can hold maybe 8 liters of coolant. The tank is a double reservoir design, so filings and metal bits can settle in the first tank, then the coolant overflows to the second tank where the pump picks it up without recycling too much junk.

I wanted to run mine on 120V instead of the 220V it is listed at, since it fit my wiring plan better. I did some web research and this pump is made (or imported) by Flair America (flairamerica.net). It seems to be one of the MC-81xx pumps which are available in 120V and 220V models.

I took the BB pump apart to see how the motor is wired. It is a simple 1/8 HP induction motor. The field coils are two identical 120V coils wired in series to operate at 240V. That is what I had expected since they probably really only make one motor with slightly different wiring for 120 or 240V. I changed the wiring to put the field coils in in parallel for 120V operation. I was careful to keep the phasing the same, and now it is 120V motor. So, problem solved. I added a cord with a regular plug on it. It doesn't look like I took any pictures of that operation, so you have to trust me.

I used some scrap aluminum (from an old computer monitor bracket) to make a bracket to hold the drain tube from the chip tray in the correct spot. You are looking at a couple of my first non-practice aluminum TIG welds here. I had to machine out the hole in the bracket to be a bit larger to hold the tubing, so there is some machining content here.

 It would make a real mess if the return tube (from the bottom of the chip pan) decided to come out of the filter basket, so this bracket will ensure that it will stay put. I then added a drain and a valve to the bottom of the reservoir so it is easier to change the fluid in the future. Without the drain, you'd have to hold it upside down while it made a mess draining out from the big hole. It seems I can never leave well enough alone!





When I was re-assembling the main lathe pieces a while ago, I cut an opening in the right hand side pedestal so I could easily get in there from the front. Of course, the hole was not quite large enough for this reservoir, so I had to make the opening a bit wider. Also here you can see the angle iron I added to make a base inside the pedestal. 15 minutes with a metal cutting blade in a saws-all with a few daubs of paint, and the opening looked like I had intended on doing that in the first place. No one (except the whole Internet) will ever know.




I installed the rear cover and a piece of painted MDF on the bottom (you can see that on the RHS of the image), and sealed it up with silicone so if some coolant leaks, it will come out the front instead of all the places where it is almost impossible to clean up.

Here is the completed pedestal with the coolant pump installed. There is a plug installed on the top of the pedestal where the coolant pump plugs in. That plug is switched with a switch on the front control panel of the machine (more on that soon). The only thing left to do here is make a cover and attach it with a few magnets. The little hose on the bottom drains anything that might spill or leak in the pedestal, so I will hopefully notice it before it makes too big of a mess when the cover is installed.





Up top,  I added some plumbing that connects up to the vinyl tube that runs up with the DRO wiring (see a previous post). I used a simple air fitting attached to the carriage (hopefully that will work OK with water based coolant). I then used an old magnetic dial gauge stand I had hanging around and made bracket to hold a piece of tubing and connected up a valve to control flow and a nozzle that can be moved around to direct the coolant wherever I need it.


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## Janger (Mar 25, 2018)

Nice job John. My bandsaw has a very similar coolant pump and tank. Emptying it is a big pain and a mess. The drain is a good idea. Would you mind posting a couple close ups of the drain details? How do you keep it from leaking where it joins the tank?

My lathe also has the coolant coming up there beside the cross slide. I find the compound tends to back into it when trying to cut a taper. So I ended use removing the coolant wand and wondered what to do about that. I like your reuse of the mag base.


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## JohnW (Mar 25, 2018)

The next sub-project was making up a new front control panel for the machine. Here is what the original panel looked like. It had a couple of large switches, and the previous owner had moved the main power switch, which was originally awkwardly on the back of the machine to the front. Those are the holes over on the right hand side.  The letters on the bottom are the labels for the feed gearbox levers.





Part of my plan is to use a VFD to power the motor and completely re-design the control wiring for the lathe so I needed to make a new control panel. Here is the new aluminum panel with the new switches installed. The aluminum is from an old sign.

The front:





And, the rear with the wiring installed. There is a bracket in the middle as a stress relief for the wires. The harness is tie-wrapped to the bracket so the wires are held solidly. You can see the countersunk screws that hold the bracket in the previous image. There are both 24V and 120V wiring here. The 24V circuits all go through the smaller shielded black wire, and the 120V wires are in the split loom. All 120V wiring has heat-shrink over the switch terminals so very little is exposed. When installed, the wire harness makes a loop, so there is room to remove the panel and pull it six inches or so away from the machine in case I ever need to get in there.





Here is where the control panel will be mounted. It is not in this picture, but I added a strip of 1/2" x 1/2" x 1/8" aluminum angle iron across the top of the opening to support the new control panel. The old one had no support there and moved a bit when pressing the buttons.





I have documented all of my wiring diagrams, and I will be posting them soon when I describe how I have the VFD and controls set up in more detail.

Edit: added the last picture.


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## JohnW (Mar 25, 2018)

Janger said:


> Would you mind posting a couple close ups of the drain details? How do you keep it from leaking where it joins the tank?
> .



Well, hopefully it won't actually leak. I haven't added coolant yet. Here is what I did. Its been a while and I didn't take pictures. I just ran out to the shop and grabbed these pictures. Hopefully they will tell the story well enough. I'm pretty sure it will work OK.

I found this fitting in the plumbing dept at Home Depot. I'm not sure what it is really for. I think it came with a big nut and a rubber washer, so I bought two (I think this is the left over one). It was only a couple of bucks. From the pictures (I don't really remember), it looks like I cut off the large end and only used the treaded parts and the plastic nuts with rubber washers.






I drilled the hole in the tank and roughed up the plastic a bit near the hole and then installed the fitting, rubber washers (one on each side) and plastic nuts and used lots of automotive RTV on all surfaces. I used some acetone to make sure there was no oil or grease. the acetone likely helped rough up the surface of the plastic as well. I tried to get the fitting as low as I could without risking leaking at the bottom. I will likely have to tilt it forward to get the last of the lube out, but I think it will be OK.

Here is a close up of the outside:





And here is what is inside. Its nice to be able to just stick the cell phone camera in there to get a shot.





The plan is to bring the tank half way out of the pedestal (like I did to get these images), let the valve overhang a drain tray, tilt it forward and be able to remove most of the liquid. Then wipe out most of the filings with a rag and re-fill. A good plan, but only time will tell if it works.

I wasn't sure if the coolant nozzle might be in the way for some project, so I used the air quick connect and the magnetic mount so it can be removed quickly, and moved where it won't be in the way. I have a taper attachment that bolts on to the end of the cross-slide, but I'm only going to install it when / if I ever need it. The coolant plumbing should not interfere with it.

Where the coolant line comes out of the base there is another valve and a T fitting so I can easily install other coolant plumbing in the future if I want to.


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## JohnW (Mar 25, 2018)

So today is really catch-up day in this saga. I dug out and edited photos last night, and took a couple more this morning, so I'm ready to go with another update:

The control panel obviously needs some nice labels. I created the following design in Adobe Illustrator. It is carefully sized to match the new control panel.







I used some acrylic sign making material (https://www.trotec-materials.com/laser-materials/plastic/trolase-reverse.html) and one of the laser cutters at Protospace to make the front of the control panel.

The panel is made out of 1/16" clear acrylic that is painted on one side with paint that provides a brushed aluminum look when looking through the acrylic, and is black on the back. You then use the laser to cut out the panel, and all the required holes, then engrave all the marking you want on the panel. The engraving burns off the paint on the back side and leaves the acrylic sort of a frosted clear where it is engraved. Then using some acrylic paints (I have easy access to that as my wife owns an art supply store), you paint the clear sections from the rear. The rear painting does not have to be accurate in any way since the paint will only be visible where the rear coating has been burnt away.

It easier to show with pictures. We start with the above graphic burn it in reverse on the back side of the acrylic, and cut the appropriate holes. It took the laser cutter about 5 minutes to do this.






Then grab some acrylic paints from my wife's studio and use a small brush and rear-paint it. No skill required:






Once it dries, the front looks like this:






And a close up:






I think it looks great. It is acrylic though, so it is not as durable as a screen printed piece of aluminum. But, since all the paint and graphics are on the rear scratches will not affect the text or colors, and would have to be very deep to really cause a problem. 

I used more mounting screws than the original panel had, and put nylon washers under each screw to reduce the chance of the acrylic getting stressed and cracking.

Once I installed it, here is what the new control panel looks like:





And:


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## buckbrush (Mar 25, 2018)

great read. F.Y.I. Colchester lathes have been made in Taiwan and now China for almost 30 years.


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## JohnW (Mar 25, 2018)

And now onto some electrical stuff.

I obtained an Allen-Bradley PowerFlex VFD used from e-Bay waaaay back when I started this project, and it has always been the plan to use it to drive the 5HP 3-phase motor on this lathe. As with most home shops, my shop power supply is single phase.

This is my installed VFD. The label says PowerFlex "40", but it is a "4", not a "40". I'm not complaining, having the wrong cover plate was the only bad thing about that e-bay purchase - I can live with that. The wires coiled on the back are for a future enhancement that I will describe when I do it.





I mounted it behind the headstock where it would stay clear of most chips and splash that might come from the lathe, but still be reasonably easy to reach, and I can easily see the display that can show things like motor drive frequency, rpm, or current draw, etc. The control knob is what I will be using for speed control. It could easily be moved to somewhere else, but I decided not to.

I welded up a stiff bracket to hold the VFD and allow the various wires to be securely fastened and reasonably well protected. The bracket is held by two 3/8" studs that are threaded into the cast iron of the headstock. My aluminum TIG welding is getter better, but not quite show-quality yet.

The metal box under the headstock at the back is the main junction box and contains the control electrics, which I will be posting about soon. Some day I will make side covers for the bracket just under the VFD to better enclose the power wires.





A side note: I had to buy three new belts for the machine as what I got with it had belts that were unevenly worn. When running the motor slowly I could hear the belts squeaking because they were riding at different heights on the pulley. They are installed here and work much better that the originals.

A bit of background on VFD's for those that might not be as electronically geeky as I am:

When using a VFD, you can use acceleration and deceleration curves to start and stop the motor, which is nice since it keeps down the stresses on the mechanical components and the peak currents that the motor draws. When you accelerate, the VFD (obviously), takes power from the electric supply grid and uses it to apply energy to the motor to speed it up. No problem there.

You can also have the VFD smoothly decelerate the motor rather than waiting for it to coast to a stop, or using a physical brake.

When decelerating, the VFD must take the energy from the motor (and all the other rotating stuff like a big, heavy chuck) and do something with it. On very large VFD's and much more complex systems it can be fed back into the grid. In smaller systems, any excess power is just dumped into what are called braking resistors to make some heat. It is possible to do without braking resistors, but if you try to use the VFD to slow down the motor much faster than it would coast to a stop on its own you will get an error on the VFD since it needs to dump the power somewhere and it can't.

The first thing VFD's do is take in the input AC and rectify it to create what is called a DC bus voltage. That voltage will be in the order of 1.4x (square root of 2) the input voltage on a single phase input, so 240V AC will create a DC bus voltage of about 340V. If the VFD had 3-phase 208 as its input the DC bus voltage would be about 360V (208 * sqrt(3)).

The VFD's then use solid state devices called IGBT's (insulated gate bipolar transistors) - basically big high voltage and high power transistors - to rapidly switch the DC bus to create a 3-phase AC current to run the motor at almost any frequency you want. The internal computer and software uses the various signals and parameters applied to the VFD to create a suitable 3-phase AC current to drive the motor.

When accelerating, or even just running, the DC bus will be re-charged from the line, and stay in the 340V range (from here on, I will consider only a single phase 240V fed VFD).

However, when decelerating quickly, the motor acts as a generator and will feed power back into the DC bus. That will make the DC bus voltage rise. If it rises to around 400V or so, the VFD will protect itself by disconnecting from the motor and indicating a fault condition (DC Bus over-voltage error). Basically it shuts down rather than exploding. After that you must reset the fault to continue. Once the VFD disconnects, the lathe will coast to a stop unless you use a physical brake.

Most VFD's have the ability to use a big resistor to dump the extra energy into to control the DC Bus voltage. As the voltage approaches 400V, it will start to dump energy into the braking resistors. It will then attempt to keep the voltage in the high-300's until the motor is stopped again and not acting as a generator.

That theory was the lead-up to me describing the braking resistor setup I've installed.

Commercial braking resistors can be expensive, but resistors are simple things, so I made up my own.

My VFD is rated to use braking resistors down to 36 ohms. Using a lower resistance risks blowing up the VFD as the resistors will take too much current. I found a good deal on a few 100 ohm, 225W ceramic resistors. Placing them in parallel provides a 50 ohm load to the VFD which will allow the VFD to dump energy but not so much as to hurt itself.

The resistors are rated to 10x that power for up to 10 seconds, so they can each handle peak loads of 2250 watts for a total of 4500 watts. At that power level they can stop the lathe in only a couple of seconds, so even if I were to cycle the lathe from full forward to full reverse several times in a row, I would not exceed the capabilities of the resistors.

Here is what my home made braking resistor setup looks like:





I got the resistors at a clearance price because they are not ROHS certified (there is lead in the solder on them). Nobody can really use them in commercial products. So, $3 each instead of about $30 each. I'm OK with the lead. They are mounted on two raised studs that are attached to a nylon rod that is then attached to the lathe. Good insulation is important here as there is almost 400V on these puppies. They are mounted far enough above the nylon rod that there should be no problem with heat getting back to the rod and causing problems.

The thermal switches JB-Welded on each side are normally closed thermal switches. They will open at about 130C. The thermal switches are wired in series as part of the enable circuit for the VFD (more on that later), so if the resistors get too hot for some reason, the lathe will shut down until they cool again. JB Weld is good for over 260C constant and 316C for up to 10 minutes, so that should be OK.

The resistors are installed in the left pedestal under the headstock where they are well protected from oil and metal chips and should have good ambient cooling.





Mounting them vertically will give the best cooling since they are hollow and hot air can rise on both the inside and outside of the ceramic.


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## JohnW (Mar 25, 2018)

buckbrush said:


> great read. F.Y.I. Colchester lathes have been made in Taiwan and now China for almost 30 years.


Thanks. I thought Colchester's were British made. Am I wrong? I don't really know, I just asking.

Mine is a clone of a Colchester that is either Taiwan or Chinese from the late 1970's (the motor nameplate indicates 1978 - assuming the original motor). I know that many companies copied much of the design once the original patents ran out.

One big different between this lathe and the Colchester Triumph 2000, which is the closest match I've seen is that the original had a clutching system in the headstock that allowed the motor to run and the spindle to be engaged via a clutch. My lathe does not have that.

In the feeding gearbox, there are also some very minor differences form the official Colchester deign (i.e. something like using 13/26 gears instead of 14/28 gears, still 2:1, but just slightly different). I don't think I have posted about the gearbox yet. I will do that some day.


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## buckbrush (Mar 25, 2018)

they were but have not been for a long while. The 600 Group still says they are somewhat British. Their higher end Harrisons are made in Britan, although they tried Chinese manufacture for them as well and failed.


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## JohnW (Mar 25, 2018)

And one more quick post for tonight:

I have the VFD programmed to run the motor from 6 to 90Hz. The nominal line frequency is 60Hz, and the motor runs at about 1725 RPM with no load at that frequency. Induction motors always run at slightly lower than their nominal RPM in relation to the frequency. At 60Hz the nominal RPM is 1800 for a two pole motor. That is because induction motors only generate torque as they slip in relation to the rotating magnetic field created by the AC current. At 1800 RPM with 60Hz the motor has zero torque, so it slows down as it cannot overcome its own friction at that speed. As it drops below 1800 RPM it starts to develop torque and eventually settles at an RPM just under 1800 RPM where the torque equals the running friction.

I tried to run the motor slower than 6 Hz, but it got quite unhappy at abut 4 Hz, slowing down dramatically and making a high-pitched squealing. That is likely caused by a harmonic of the 16KHz switching frequency used by the VFD to make the AC that is driving the motor. 6Hz seemed like a good low-end frequency to stay away from any motor problems.

The higher the speed you select (beyond the nameplate frequency of 60Hz), the lower the motor torque will be. The VFD can in theory generate up to 240Hz, but the motor would have very little torque at that speed. Also the motor was designed to run up to about 1800 RPM. Going very much faster can be hard on the bearings, depending on how well it is balanced, and the centrifugal forces get larger at higher speeds.

I found some information in the web that indicates that almost all motors of 10HP or less can be run at 2x their nameplate frequency, but I thought I'd play it safe and stick to 1.5x or 90Hz.

That makes the speed range of the motor from about 150rpm up to about 2600 RPM when driven by the VFD.

With lower frequencies (than the nameplate frequency) the motor maintains almost all of its torque and runs very smoothly with even torque. That's great so the little VFD knob can be used to adjust the speed instead of changing a lot of gears. 

Except there is a problem: The slower the motor goes, the less cooling it gets from its built-in fan because the fan is turning slower (obvious). However, at lower frequencies, it is still making the same amount of heat. So running it say, 20 Hz under load can easily over heat the motor.

My solution:





This is a 24V 1.5A fan that blasts a huge amount of air. I got it out of an old mainframe computer 20 years ago. The VFD has a small relay built into it that can be programmed to do various things. I've programmed it to run this fan whenever there is power applied to the motor. Inside the control box (more on that later) there is a small 20V laptop power supply that runs this fan. The fan still pushes a huge amount of air at 20V.

The bottom line - even when running the motor slow, it should still have lots of cooling.


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## PeterT (Mar 26, 2018)

Very nice restoration/upgrade project, you have built a nice machine there!

Regarding those big resistors, that's exactly what I was wondering about when people set up proximity switches on the lathe bed. I've seen a video of single point threading. A switch sensed carriage position & the motor came to an almost abrupt stop. I can visualize the signal could say 'ramp down' maybe over several seconds, but couldn't help but thinking short duration 'braking' must involve dissipating quite a bit of energy. Would you say the resistors would be a common part of any VFD configuration if you wanted this capability or because you have more HP? For example my 14x40 lathe has a 1.5HP motor 220v 1P. 
I remember you posted some good info about VFD lathe motor conversion.
https://canadianhobbymetalworkers.com/threads/lathe-power-off-timing.812/#post-7808


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## Tom Kitta (Mar 26, 2018)

Given that the lathe has change gears what is the advantage of a VFD? More fine tuned speed control? Can slow down all they way to 10 rpm if needed at a cost of torque? Can slightly over speed (within bearing limits/ other limits)? Faster stop without having to hit the break (at the cost of having extra resistors installed)? 

Your lathe looks like a smaller version of my Indian lathe - maybe if you need more challenging project you can take a look.


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## Dabbler (Mar 26, 2018)

I have a friend that put a VFD on his 18X72 10HP lathe... He added a solenoid to the resistive breaking circuit to also engage his drum brake. He gets very consitent 1 turn stopping in a single revolution at 400 RPM!  I just shake my head when I see it work - wow. The benefits of advanced VFD programming and good braking resistors.


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## JohnW (Mar 26, 2018)

Peter:

With braking resistors, the lathe can slow down really fast. It can come to a stop faster than it can accelerate. If it has a 2HP motor (for instance), and it takes 1 second to go from 0 RPM to 1000 RPM on the spindle, it can go from 1000 to 0 in less than 1 second.

That is because when accelerating, it has to fight friction, when decelerating, friction is helping.

The VFD can be told to use whatever acceleration curves you want. For most operations, I have mine set to a 2-second ramp up/down which I think is a reasonable compromise between waiting for speed to change, peak power usage, and wear and tear on mechanical things. When deceleration is triggered by the brake switch on my machine, it switches to a 0.5s ramp down. The bottom line is I will only use the brake lever when I really want it to slow down. In normal stops, the 2s ramp down is fine.

If I have my big 4-jaw chuck on spinning at 2000 RPM, it will need to use the braking resistors to achieve a 2 second stop time.

It does involve dissipating a lot of energy to quickly stop a big rotating thing. That is why the resistors are big. My motor is rated at 14A @ 208V, so that is around 3000W. The motor also can generate about that amount of power when running as a generator, so the resistors need to be able to absorb that sort of power. In my case the resistors are rated at 4500W for up to 10 seconds. in reality, the braking circuit of my VFD is only rated to feed about 10A into the resistors, and in my case with a 50 ohm load, it will only be able to feed about 8A which at 400V is about 3200W. Intermittently, my resistors can handle that easily. Used continuously, my resisters would quickly (< 30 seconds) get dangerously hot. That is why I installed the temperature sensors that will shut down the VFD if the resistors are too hot as a just-in-case.

Another analogy is comparing the brakes on a large aircraft to those on a train. One needs to dissipate a huge amount of energy for 10-20 seconds, but never more than every 20 minutes or so (worst case, it has to abort a take-off 20 minutes after landing). The other needs to be able to dissipate an even larger amount of energy almost continuously when going down a mountain pass. I've installed the aircraft version.

Are the resistors required with a VFD? Not really. Only if you want to be able to electrically slow the machine much faster than it would normally glide to a stop. In my case, I found a good deal on the resistors, and it was a fun project to built them, so it was worth it to do.

There is another way that VFD's can apply braking. It is called DC braking. In that case the VFD applies a DC current to one or more of the field coils which causes a stationary magnetic field (instead of the rotating field that normally drives the motor). In that case the stopping is less controlled, and the heat ends up in the armature and field coils of the motor. The motor is large. As long as you don't do that continuously, the heat will not be an issue. Doing that continuously could be a bad thing.

In resistor loads rated for continuous use (like what might be used to control a down elevator full of people), there is an array of heating elements and fans to be able to continuously dissipate the energy. That is a large and expensive sort of thing - especially in a safety related use like with elevators. In that sort of implementation, usually the DC busses of several VFD's will be connected in parallel, so the power used by the up elevator can be fed by the down elevator. The big dummy loads are still required in the evening when all the elevators might be going down full of people as everybody goes home. At that point, a reverse VFD that takes the excess power in the DC buss and feeds it back into the grid might also be used. the elevators might even be programmed do go down more slowly than usual if there are several moving down at once.

The point is that you have the full power of the motor to decelerate the machine when using a VFD, not just internal friction.

If you have a good physical brake (like one that can absorb 5HP of power), the brake can stop it twice as fast as a 2.5HP motor. The VFD does it with no wear to anything though. Like using your transmission to slow down your car when going down a hill instead of the brakes.

If you want to stop really, really fast, you might need the help of a really good physical brake. Remember though that braking that hard can be hard on the gears since you are snapping it from running under power to reverse very quickly and will likely be taking at least some of the gears across their lash and impacting once the lash has been taken up. If the brake were to be on the spindle it would be a lot easier on the head stock gears.

Tom:

Those are the main advantages.

Yes, change gears give you several speeds. Usually more than enough, but only in steps. The variable speed motor allows you to achieve any speed, or make small speed adjustments very easily. It also gives you a wider range of speeds - probably down to 25% of your slowest gear to 150% of your fastest. So, a machine that had geared speeds from 100 - 1000 RPM could be extended to 25 - 1500 RPM.

Is the variable speed control required in most cases - no. Is it a nice to have - yes.

One case where variable speed can be useful is when facing a large surface. You can start the operation at maybe 20Hz with appropriate gearing to have a good surface speed on the outside of the part. As you work towards the center, you can increase the frequency to the motor. That way you can maintain an acceptable surface speed over maybe 90% of the face, rather than only maybe 25% when facing at a constant RPM.

Another is when machining to a shoulder (like threading that Peter mentioned). With the VFD, you can slow it right down as you get close, and then when you hit the brake at the last moment, it will likely stop in much less than a quarter of a turn.

Slowing down the frequency does not cause a significant reduction in torque at the motor (until you get really slow - the reason I've limited mine to a minimum of 6Hz). When running at 10Hz, for instance, the magnetic fields in the motor still come up to full strength and pulls the armature with the same force. Power is RPM x torque, so there is less power coming out of the motor when running at lower frequencies, but roughly the same amount of torque at the motor.

When you achieve the lower RPM at the spindle with gearing, the gearing increases the spindle torque and you maintain the same power output, but with higher torque at the spindle.

With a VFD it is normal to use both gearing and frequency control. Set the gears to the approximate speed range, and then us the VFD to adjust the speed from there. You can easily change speeds while cutting as you see the results of the cut. In most cases I will probably run my VFD between 45 and 80 Hz.

The torque is much smoother with a 3 phase motor as when compared to a single phase motor. That is probably the biggest advantage of a VFD - the ability to use a 3-phase motor. It is the equivalent of a 2 cylinder engine when compared to a 6 cylinder engine with power strokes spread evenly around the rotation of the crankshaft. The 3-phase motor provides almost constant torque, while a single phase motor must use inertia to glide between times of no torque between its "power strokes". Compare a 2-cylinder Harley (very unevenly spaced power strokes) with a 6 cylinder Goldwing. The difference in smoothness is night and day. Constant speed on a lathe can significantly affect surface finish by keeping a constant chip load..

The bottom line is that I'm an electronics geek in addition to a machining geek, so playing with and learning about VFD's and motor control is also fun for me. Also, the VFD is necessary when you have a 3-phase motor and only single phase service. Once you've been forced to have a VFD, you may as well use all of its features.


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## JohnW (Mar 26, 2018)

This post is the first of several about the lathe controls in general. Now that I've built it, I'll describe how all the controls work, and then go into how I implemented it all in further posts. I spent a lot of time designing all this, so it might be useful if someone else is considering doing something silly like completely re-wiring a piece of their equipment.

So first there is the main control panel. I've already posted a similar image, but here it is again for reference:




Power:

This is a momentary switch with the center position being off.
Pressing it up engages and latches the main power to the lathe.
Pressing it down unlatches the main power relay (contactor) and turns the main power off.
Turning the power off while it is running will cause it to coast to a stop.
When the power is turned off, the VFD takes about 30 seconds for its capacitors to drain to a level where it displays an input under-voltage fault, and then the display finally goes blank after about 10 more seconds.
It takes the VFD about 10 seconds to boot itself up when power is turned on. That is one of the reasons for the Motor Enable switch, so the VFD is not continuously cycled, which is not particularly good for it. It is better to cycle it less often.
Turning off the power also brakes the enable line to the VFD, so the VFD will instantly stop powering the motor.
It is important to use momentary contacts on the main power so if there is there is a power failure that the lathe will not automatically power itself back on when the power comes back on.
There is a 120V plug on the back of the machine that provides 120V (limited via an internal 7A breaker) to power external things like the DRO and some extra lighting I will eventually install above the lathe. That plug is live whenever the lathe is powered up.
Motor Enable:

A normal on / off switch.
The VFD has an enable circuit that has several switches in series. This is one of them.
If you set this to disable, it tells the VFD to not run the motor under any circumstances. Other switches in this circuit are the brake resistor over-temp switches, and an extra contact on the main power relay.
All of the switches in the enable circuit must be closed in order for Motor Enable to work, so a wiring or switch problem will tend to disable the motor rather than accidently enable it.
This is useful when working on setups. Like maybe adjusting a 4-jaw chuck. It is not necessary to turn the whole machine off to safely have the motor disabled.
The auxiliary power plug stays on when the motor is disabled so the lights and DRO remain on.
Turning this off while the motor is running will cause it to coast to a stop.
Coolant Pump:

This one's pretty simple. It simply turns the power on and off to the coolant pump.
I probably could have integrated this with the motor or the enable circuit so the coolant would only be on when the motor is on, but I choose to keep it simple for once.
Jog:

Another momentary centre off switch.
Pressing down gives a forward jog command to the VFD. It runs the VFD at 6Hz with a 0.5sec up and down ramp. It is easy to just rotate the chuck a fraction of a turn with a flick of this switch.
It has no affect if the motor is in regular forward or reverse motion as commanded by the F/R lever.
Pressing it up actually runs the motor momentarily in reverse. I had planned this to be just like forward jog with different speeds and ramps, but the VFD won't do it without disabling some other stuff that I think is more important (I would need a fancier VFD with three digital inputs instead of just the two mine has).
Still, it works OK as reverse jog. A brief flick upwards jogs the lathe backwards without actually going very fast or very far. The lathe is programmed with a 2 second ramp for normal operations, so a 1/4 second flick does not go very far or fast.
Power Off:

Not called Emergency Stop since what it really does is turn the power off.
Still a good thing if for some reason it is running (or on fire) and does not want to stop.
If the lathe is running it will coast to a stop when the power is off.
It is much faster to stop the machine using the brake lever across the bottom, and the Motor Enable function is better for doing setups, so this is unlikely to be used much.
Next I'll show the normal direction and brake controls.


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## JohnW (Mar 26, 2018)

Here is the schematic for the control panel.


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## JohnW (Mar 26, 2018)

On to the Forward / Neutral / Reverse Lever:

I may have posted this image before, but over on the bottom right is the FNR lever. The bottom shaft has a keyway running the length of it. The lever has a key that runs in that keyway to rotate the shaft and then move the shaft on the bottom left of this image in and out. When I rebuilt the machine, the key was very loose from wear, so I made a new one. Sorry, no pictures of that.





I put the bracket that holds the FNR level in the mill and re-machined the slots that are used as the detent. They don't look great in this image, but they were way worse before I cleaned it up.  The lever was very easy to knock from the neutral to the forward position because the side of the deeper slot was rounded off. The lever has a roll pin that sticks out and sits in the deepest slot for neutral, and is limited by the wider slot for the forward and reverse directions. I ended up drilling it out and installing a larger diameter roll pin and making the slot wider to be able to machine off the worn part.





When the FNR shaft near the headstock moves in and out, it move this HDPE ramp that I made (see a previous post) past two micro switches on the back of the lathe. What I inherited here looked like a poor repair of something that had been broken in the past. It was not good.










When using the FNR lever there a couple of things to note:

If the lever is moved from N to F or R the motor turns on in the correct direction based on the contacts that are made by the micro switch (obvious).
Those wires control an interlock relay in the control box that signals a forward or reverse command to the VFD (more on that later).
If the  motor is turned off for any reason when the lever is in the F or R position, it will not go back on until the lever is returned to the N position and then moved to F or R again. This is the safety interlock.
The motor could be turned off because the brake lever was pressed. In that case the interlock relay does not allow the motor to restart until the lever is returned to the neutral position. You don't usually want the motor to restart after pressing the brake even though the lever is still in the F position.
The motor could also be turned off because the motor enable switch was switched off. In this case the VFD is programmed to not restart the motor if it is enabled while a forward or reverse command is present.  The lever has to be returned to N first. Again, a safety interlock.
If the lathe power is turned on with the FNR lever in F or R, both the VFD and the interlock relay will prevent the motor from going on until the lever is returned to the neutral position.
I've attached the FNR switch wiring diagram as a pdf.


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## JohnW (Mar 27, 2018)

The next thing is the brake lever. This is the manual foot brake that runs along the floor under the bed. This is what it looked like after being repaired, painted and installed. The lever is held by a small stub shaft in a bushing on the right side. The left side has an extension shaft that goes through a bushing through the left pedestal where it actuates a vertical rod that actuates the actual brake.





The problem is that the shaft on the left side is held in the pipe of the lever by a couple of pinch bolts. this was never very strong and it looks like several attempts were made over the years to repair it when it came loose. Stomping on the brake lever with your foot puts a lot of force on this.

The rod with yellow paint on it in the background was quite a loose fit in the pipe and several attempts had been made to make pinch bolts and through bolts to hold it into the pipe. All of the fixes eventually failed. You can see some of the remnants of that work on the lower part of the image.

My plan was to drill out the lever a bit to clean it up, then insert the short piece of pipe sitting on the workbench and weld it in place with a bar that could hold larger pinch bolts that would have a half inch of thread to bite into. Here is what I started with:





A little cleaning up of the inside of the lever with a large drill bit, and the short bit of re-enforcing pipe could be hammered into place. I had already run a drill bit through the inside of the pipe to clean it up.





Once it was in, I ground out some of the existing holes so I could securely weld the inserted pipe into place.





Once the pipe was welded in place, I added a 3/8" thick bar on top, and drilled and tapped it for 3/8" (grade 5) bolts. The bolts now have over 1/2" of thread to bite into (the new pipe, the old pipe, and the bar) so they should be pretty strong and can be tightened without danger of stripping.





The ID of the inserted pipe is slightly smaller than the shaft, so I machined it down to be a good fit - a few thou clearance. You can see some of the previous attempts to attach this shaft to the brake lever.





To make sure the shaft does not rotate once the bolts are tightened, I machined two flat spots on the shaft for the bolts to clamp down to. Ha-yoo, some real machining pictures!!!





Close-up. Not really beautiful machining, but it is all hidden anyway.





Then I painted it, assembled it, and you can see the finished brake lever in the first image in this post.

I'll get into the brake electrical stuff in the next post.


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## JohnW (Mar 27, 2018)

Here is the next part of the brake mechanism. This is looking through the left hand pedestal from the end. You can see the brake lever from the previous post in the opening. This picture was taken before the braking resistors were installed. They would be in the upper right corner of this picture. I made up a new bracket to hold the brake switches. Originally there was only one switch and it used a bit of an ugly bracket that was mounted a bit further to the left than my new switches. The big spring is what keeps the brake held in the off position.





Here is a close-up of the switches and the brake lever. I added the tab on the right side of the lever to actuate the switches. The switches are setup up to provide two signals depending on how far the brake lever is pushed. The right hand switch clicks with the slightest movement of the lever. That way a light tap on the brake lever will tell the lathe to stop and use a normal decel curve (2-secs). A light tap is not enough to actuate the physical brake. The physical brake is applied by pushing the yellow bar up. Look way back to an early posting in this thread to see what happens up there.





Pressing harder on the brake lever will actuate the physical brake and the left hand switch. That switch sends a DC braking signal to the VFD telling it to stop as quickly as it can.

The micro-switches have a short piece of (split open) plastic tubing tie-wrapped over them to protect them from stuff falling on them. If a big metal filing were to fall on top of them it could short the contacts, so this way that will not happen. The extra holes in the bracket are used as a stress relief for the cable running back to the control box.

So the manual brake works as follows:

Press it lightly to stop the motor normally using a 2-second ramp-down. To restart, the FNR lever must be returned to N and then to F or R.
Press it hard to both apply the physical brake and tell the VFD to stop the motor as quickly as possible. This is the real emergency stop mode since it is way more effective than just killing the power. The lathe is stopped as quickly as possible in this mode.
Use this hard press on the brake for emergency stops, and to quickly stop when machining up to a shoulder

Here is the wiring diagram for the brake switches:


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## Tom Kitta (Mar 27, 2018)

You know you could write a small book called "Restoring my lathe" or "Lathe restoration and improvements".


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## buckbrush (Mar 27, 2018)

Yes, best posting on the site.


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## PeterT (Mar 27, 2018)

So relating to my example of threading up to a defined shoulder (ie. a position on the work that you don't want the cutting tool to cross over). Could you set up a limit switch ahead of the shoulder position so that when it sees the carriage arrival, it initiates a defined ramp-down in the VFD? Lets say it didn't even have to be a rapid stop, something conservative like 2 seconds. If I understand correctly, could you could still reliably count on this same zero rpm stop position for each repeated threading pass? Maybe you would have to tweak the sensor position with a few dry run passes to ensure the cutter point comes to a stop inside the target relief groove. Or maybe knowing rpm, time & thread pitch you could figure out the position. Anyway if it works this way, it would eliminate the typical threading disengagement lever pulling rigmarole, no?

_The VFD can be told to use whatever acceleration curves you want. For most operations, I have mine set to a 2-second ramp up/down which I think is a reasonable compromise between waiting for speed to change, peak power usage, and wear and tear on mechanical things. When deceleration is triggered by the brake switch on my machine, it switches to a 0.5s ramp down. The bottom line is I will only use the brake lever when I really want it to slow down. In normal stops, the 2s ramp down is fine._


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## JohnW (Mar 27, 2018)

Peter:

Yes you could do that. If the standard decel would work for you, the sensor switch could just break the motor-enable circuit (I will post the full schematic soon), and that would immediately initiate a 2-second decel. Alternatively, you could change the decal to 0.5sec or something more aggressive and do the same thing. It should be pretty consistent as to where it stops given the same RPM, chuck and work piece. It is easy to reprogram the decal rate for a use like this, and put it back when you are done.

You do need to be careful in stopping a carbide bit (if you are using that) while it is engaged. I have broken more than one by stopping in the middle of a cut. It seems to put a ton of stress on the bit as it comes to a stop and "ping" off comes a corner of the cutter.

The only problem with doing this in my set-up is that I've already used up all of the VFD input interfaces to do other things like F/R job, braking, etc. If you override one of the other inputs temporarily it is certainly possible to do.

If you wanted to be a bit fancier, the VFD can also be programmed and ordered around via an RS485 interface. An Arduino microcontroller could easily be programmed to interface to the VFD on the RS485 interface (RS485 is an industrial version of the RS232 interface that is often used by PC's and less industrial stuff). The RS485 interface can tell the VFD to do all sorts of things that override what the normal inputs do. 

You could, for instance, use two limit switches. The first senses when you are maybe 1/4" from the end which would then ramp the VFD down to minimum speed over maybe 1 second. The second might only be 0.010" from the end, and tell it to stop as quickly as possible, which would happen very fast from a slow speed.


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## PeterT (Mar 27, 2018)

Yes, that's what I've heard about carbide threading inserts in particular. The don't like sudden load interruptions like entering an existing thread with too much in-feed. They don't like stopping mid cut. And they typically like to run at higher speeds. All of these factors collectively working against you on a manual lathe. One more for good measure - metric threading on an IMP machine, most say don't disengage the threading half nuts.

I figure 99% of all external & internal thread jobs should have a relief groove incorporated on one side (meaning slightly deeper than the maximum thread depth). So if a VFD could be controlled to reliably terminate when the V point is inside the groove, that would be a very desirable feature over & above the VFD speed control advantages.


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## JohnW (Mar 28, 2018)

So now its time to get heavier into the electrical controls. After thinking about all the controls and switches, I designed the electrics. The actual order was:

Fwd / Rev switches - This was pretty obvious 2 micro-switches and an 8-conductor cable back to the control box. I used 8 wire cable when I only needed six because I had some very flexible, shielded, and tough 8-conductor cable that was ideal for this.
Brake Switches - I know I wanted to detect the two braking stages, so again, two micro-switches, and 6 conductors back to the control box in an 8-conductor cable. I'd figure out how to make it work later.
Once I was getting close to having most things rebuilt, I read the VFD manual several times, scratched my head for a while, and designed the overall schematic.
The VFD has 10 low voltage connections, so I ran a 12 conductor cable between the VFD and the control box. It is always a good idea to have a couple of extra conductors.
Once I had what I thought would be a working schematic, I found a way to arrange all the required components and terminal strips required on the original phenolic board that fit in the original wiring box for the lathe.
I drew up the schematic and all the connections using Visio. This is complex enough that if I ever needed to look at it again in a couple of years, I would need it all documented. Just to get the wiring right in the first place it was a good idea to have nice readable schematics to help me keep everything straight. I still made a couple of small mistakes!
Then I wired up the internal control board connections.
Finally, I installed the control board and connected it to all the wires that came in from the various external devices.
Set all of the VFD parameters to what I thought was the correct settings to make all of this work.
I tested it, found a couple of mistakes, and fixed them. Nothing serious here, I mixed up a couple of wires from the NC and NO contacts on a couple of micro-switches.
I spend some time tuning up various parameters in the VFD. It didn't all work out as I had hoped, but the major functions were fine. The only real issue was that I could not get reverse JOG to use a low frequency, or a different acceleration ramp. The result is that reverse jog is really just another easy way to select reverse momentarily, instead of reverse at a low speed. I can live with that.
So, here are some photos:

First, the control board. The left and upper portion (mainly black stuff by coincidence) is 120V and 240V stuff. The main 240V single phase input comes into the fuse block on the upper left. The power output to the VFD leaves on the terminal strip on the far left.

There is a small 1.6A breaker in the fuse block that provides current to the 120V portion of the control circuits from one of the input phases. That way any issue with the 120V control circuits doesn't end up in a huge (nasty and probably exciting) short circuit fed from the 30A slow-blow fuses, but instead quickly opens up the 1.6A breaker. That circuit needs far less than 1A to operate.

The big relay is the main power on/off relay (it was one of the originals from the lathe), and the smaller relay in the upper right is a 120V relay that is used to de-latch the main relay.

The  longer black terminal strips are where various 120V things connect.

The smaller white terminal strips are used to connect to the various low-voltage controls. All of the terminal strips are raised up on HDPE strips to make room for the wiring to run around below them. That way it is easier to install the external wiring on top of it all.

There are also two other breakers that are mounted on the control box itself:

A 7A breaker controls the auxiliary 120V circuits, which includes the coolant pump, the rear auxiliary plug that supplies some additional lights and the DRO AC adapter, and the 20V supply for the fan.
A 2A breaker on the 20V DC circuit that supplies the cooling fan, and some future electronics that I have planned.
So, here is the unwired control board:





And the control board with the internal wiring installed. The red and yellow wires hanging off the side go to the 7A AC breaker.





Another view of it. I tried to use wires of the same color to control similar portions of the circuit. The smaller relays are mounted in terminal blocks, so they can be removed easily and have nice screw terminals.





And what it looked like once it was installed in the control box and connected up. I installed 1/4" nutserts to hold the cover on instead of the sheet metal screws that were originally used. The 20V supply is mounted on the right side, the 120V 7A breaker and the 20V 2A breaker are mounted on the lower right.

All of the wiring comes up from the bottom, with either the hole labeled as to what is coming in there, or where several low-voltage cables come in together, there are labels on each cable to identify it. Nothing really fancy here, just white electrical tape, and a quality permanent marker (Staedtler).

The high voltage stuff is on the left, and the low voltage stuff is on the right. It is always a good idea to separate the high and voltage stuff as much as possible when they are combined in a box.

The white/black/green harness that exits out of the bottom of the picture goes to a 3-pin connector that connects to the 120V plug that is mounted on the cover. The connector allows the cover to be removed instead of hanging by the wires.

Some judicious use of wire ties keeps it reasonably neat.





I've attached a PDF of the layout document I created for the control box.

The next post will go into detail on the high voltage wiring.


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## JohnW (Mar 28, 2018)

Here is the schematic for the high voltage (240/120V) circuits. I've also attached a higher resolution PDF of this.





The 240V spilt phase AC comes in via a standard stove plug that is connected to a pair of 40A breakers in the panel. The connections to L1, L2 and Neutral come in on the bottom left.
The first thing in the circuit is a pair of 30 slow blow fuses that protect everything. Those two circuits go to the main contacts on the big relay (aka contactor) and then on to the VFD. There are three wires connected to the VFD, since it is a 3-phase input VFD. Two of the phases are connected together. There are a couple of reasons to do it this way:
Some 3-phase VFD's will signal a fault if one of the three input phases is dead. That is a good thing if you are connected to 3-phase power. In that case you want to know if you have a dead phase. Connecting the extra input like this will usually fool the VFD.
It makes life a little easier on the VFD in that two of the sets of input rectifiers will share the load. The third still needs to take the full load. That is not a big difference, but you may as well do it since it is easy.
The VFD needs to be de-rated by something like 30% in this configuration since it is only receiving power pulses from the AC line 120 times a second instead of  the 360 times a second it would receive with a 3-phase input. That puts more load on the input diodes and the DC bus capacitors. I will likely never run the lathe hard enough for this to be an issue.

The braking resistors simply connect to the VFD. The VFD controls them. Nothing fancy there.
The three phases from the VFD are fed out to the 3-phase motor. Again pretty straight forward. The VFD controls the motor based on signals form the low-voltage signals that are connected to it.
One of the phases from the main relay feeds a 7A breaker that runs the coolant pump (via the front panel switch), the 20V DC supply and the auxiliary plug. Again , pretty straight forward. That means that one leg of the input 240V will be loaded a bit more than the other, but only by a couple of amps, so it is not a big deal.
The main relay control is a bit more complex:
The control circuit is protected by a 1.6A circuit breaker. That allowed me to use relatively thin wires in this circuit. Also since these wires head up to the control panel, if there were ever a problem, there would not be a lot of current involved. This circuit uses a maximum of less than a quarter of an amp, so the 1.6A breaker I happened to have around is more than enough and small enough to protect the control circuit.
The "on" side of the main power switch on the front panel will energizes the relay when it is pulsed.
The relay will then latch on because the lower of the three contacts will feed power back to the coil once it has been energized.
The power in the relay coil has to go through two other devices before the relay can be (or stay) energized:
The E-stop switch. If the e-stop switch is opened, it will not allow the relay to close, and if the relay is already closed, it will remove the power and the relay will open and shut down all the power.
The Off-relay is normally closed, but is opened by a pulse from the front panel off switch. Once it opens the main relay releases and power is turned off.


And that's it for the high voltage control. The important thing here is that the main relay will release if there is a power failure, or if the e-stop switch is pressed. When it is released there is no power being consumed by the lathe.

I had thought about a pilot light to indicate that the power is on, but did not bother because the VFD display indicates that the power is on. Still, it would not have been too bad an idea to put a pilot light on the main panel.


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## JohnW (Mar 29, 2018)

Now on to the low-voltage schematic. This is a lot more complicated, so I will present it in several stages. Here is the schematic for the VFD enable circuit, and the cooling fan circuit.



The VFD is controlled by a 24V circuit that it provides the power for (VFD terminal 11). The VFD cannot provide a lot of power on this circuit (maximum 100ma), but that is more than enough for what I am doing here.

The VFD Enable input (terminal 1) must be connected to 24V for the VFD to run the motor. The VFD is programmed to provide a normal decel ramp when the enable line is disconnected.  It also provides a safety function such that if Enable and a motor run command (i.e.: Fwd, Rev, or Jog) are both present at power up or when Enable is activated, that it will not run the motor until the motor run command has been removed. That prevents the motor from unexpectedly running.

The enable circuit is quite simple. Since it is a normally closed loop (all switches must be closed and the wiring must be intact), any wiring problem will disable the motor until the problem is repaired. Failing off is much safer than the possibility of failing on. It is a series circuit including the following. 

The front panel Motor Enable switch,
The two brake resistor over temperature sensor switches. This is a safety circuit that will prevent the motor from running if either of the brake resistors is too hot. The thermal switches will open long before the resistors are dangerously hot, they should still have the capacity to help in one more stop if the motor is currently running and the VFD tries to stop it using the braking resistors. The VFD will not run the motor again until the resists have cooled again. The thermal switches have a hysteresis of about 30C, so they will turn off at about 130C, but not turn on again until they cool to below about 100C.
An auxiliary contact on the main power relay. This means that if the main relay is de-energized, that the VFD will also stop powering the motor. It won't be able to continue to power it for long if the motor was running since it will have had its power removed as well, but it does have some large internal capacitors on the DC bus. If the motor is not running when the main relay turns off, this prevents the VFD from executing any motor run commands. This is really not a very important function, but I had an extra contact on the main relay so I used it to signal the VFD.
The motor fan circuit is also quite simple:

The VFD has an internal relay that is programmed to be turned on whenever the VFD is providing power to the motor.
The motor cooling fan is powered by the 20V supply and turned on whenever the VFD internal relay is turned on.
I would have liked to have the motor cooling fan stay on for 30 seconds after the motor has run, but there was no VFD option to do that and I did not think it was important enough to design a delay circuit for that.

The "Instrumentation" box is some future electronics I have planned to provide a digital readout on what the lathe is up to. It is not installed yet.


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## Colten Edwards (Mar 29, 2018)

JohnW said:


> Here is the schematic for the high voltage (240/120V) circuits. I've also attached a higher resolution PDF of this.
> View attachment 2955
> I notice that you have 2 wires coming from one terminal on the main power relay. Seems to me that you are missing the connection to AC neutral on the VFD and I assume one of those wires should actually be ac neutral


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## JohnW (Mar 29, 2018)

Nope. The VFD does not use a neutral line. It strictly connects to the 3 hots in a 3-phase system, or the 2 hots in a spilt phase system.

If you are referring to the two lines leading from one contact on the main relay to the VFD, that is somewhat explained in the text. Since it is a 3-phase VFD, I have all three phases connected to the two hots that are available. Some 3-phase VFD's will complain if one of their phases is not live, but they are generally not smart enough to detect that two of the phases are identical, or that they are really only receiving single phase power with the phases 180 degrees apart instead of 120 degrees apart as they should be in a 3-phase system.

The diagram does show how the lathe is wired. There is a 4-wire cable running from the control box to the VFD:

Phase-1 - Black -  Input line-1
Phase-2 - Red -    Input line-1
Phase-3- White -  Input Line-2 - Should have blue tape on this wire to indicate it is hot, and not actually a neutral.
Ground - Green - Ground.
The second line off the other main relay terminal goes out to the 7A breaker for the auxiliary 120V circuit. Since that is a 120V circuit, it returns to neutral.

Update: added 3rd paragraph.


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## Johnwa (Mar 29, 2018)

The drawing shows 3 wires going into the vfd.  I think he was referring to the two wires off the top power relay terminal.  

I’m early in the process of properly wiring up my vfd.  I wasn’t planning on an e-stop that shuts off all power.  I’m now rethinking that plan.


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## JohnW (Mar 29, 2018)

OK, so on to low-voltage schematic part 2:




I've added the brake switches and the Fwd/Rev switches to this diagram.

The 24V signal goes through the NC (normally closed) contacts of both brake switches to feed the F/R switches.
If either switch is open (the brake is pressed), the power is removed from the F/R switches, which will remove any forward / reverse / jog signal being given to the VFD.
If the brake lever is pressed lightly, only the stage-1 switch will open, which removes any go signal from the VFD as described above. If the motor is running it will ramp down to a stop since the VFD is just seeing its go signal being removed.
If it is pressed further, the stage-2 NC switch will open and connect 24V to the NO contact. That will then send a signal to the VFD DC Injection Stop terminal (#6). When the VFD sees that, it uses DC injection to bring the motor to a stop quickly. With that and the physical brake, the motor comes to a stop very quickly.
Here is a great benefit of documenting what you do. In re-reading this post, I realized that the brake switch contacts are actually labeled wrong here, the description above is also wrong. The NC and NO labels should be reversed. The brake switches normally sit partially pressed in, so their NO contacts are closed and the NC contacts are open. When the brake lever is pressed, one or both of the switches will be released moving the switches to their NC positions. I will update the diagram and re-post it. 

Sorry!


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## RobinHood (Mar 30, 2018)

Excellent write-up! This is a great tutorial for someone wanting to go down the same road and improve the wiring on their lathe.


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