Metal lathe options

[VicHobbyGuy]

Personally, I don't think much of Facebook groups. I am only there for marketplace.

I agree. I REALLY don't like FB Marketplace but I have to go there for the same reason I use the FB mini-mill and 7x groups: it's where the action is. For buying and selling in Victoria, usedvictoria used to be the go-to place. Now, I put identical ads both there and in FB marketplace - but 80% of the buyers come from FB.
When I got a 7x lathe a couple of years ago, I split my time between FB and the old yahoo 7x groups (now groups.io). Now it's 95% FB because the activity on the other group is sparse.
Things change.

 

[whydontu]

I spent three weeks in Israel, Jordan, and Egypt last year. Mostly looking at really, really, really old stuff. Anyone here want to make 500 almost identical 20ft high x 2ft diameter fluted rock columns, with matching decorative carved caps? Using only wooden mallets and bronze chisels? The human hands and brain does the work, not the machine. Within the work envelope of a 7x14 lathe, anything that can be done on a Monarch or Hardinge can be done on the 7 x14. It takes practice, perseverance, and the willingness to ask questions, experiment, and be open to new ideas. @Chris Cramer sounds like he’s willing to do this.

 

[Susquatch]

And, sometimes "Get a bigger lathe" is the correct answer, too.

Yes, I can imagine times when that is true. But I'd like to think that advice would only get given when it's apparent that it's necessary and then only with humility - a rather tough emotion to convey.

 

[Chris Cramer]

You can also see that I put a very small radius on the tip as well as honed all the edges. I also marked the top as Up.

All the blanks I've received from Amazon come with a slight angle on both ends in one direction which I see you used for your side relief. The top I can tell is slightly concave with a curved positive edge, but because of the camera angle on the second picture, I can't tell for sure if the end is slightly tapered on both sides giving it a more narrow tip.

 

[Bandit]

After a post by VicHobbyGuy, I took another look at the Vever 7X lathes, they don't have a 2 speed transmission in them! (All or some, not sure). Learning again!
For those that have these lathes, what rpm would you be likely turning for 1.25 ss shaft? A ball park. I know, material dependant, etc. Using HSS, type of carbide?
I know, lots of variables. The general HSS tool bit idea of slow it down (rpm, 10, 20, etc.) does not seem to work as well here.
An idea, good, bad?

 

[Susquatch]

All the blanks I've received from Amazon come with a slight angle on both ends in one direction which I see you used for your side relief.

Although I sometimes do, I don't believe I used that relief this time. But I didn't do a fine grind or a water grind or any honing on the whole relief so it might look like I did.

The top I can tell is slightly concave with a curved positive edge, but because of the camera angle on the second picture, I can't tell for sure if the end is slightly tapered on both sides giving it a more narrow tip.

The tip is not really concave either (or shouldn't be anyway). If it is, it was accidental and inconsequential. It is ground down a bit to give you some elbow room to get on center. It also has a very slight negative edge that was caused by honing a drop shelf. It shouldn't affect anything. Maybe in hind sight the drop was a bad idea. I just didn't know what height you needed until after I made it.

The nose itself has a very small tip that transitions to a bigger radius to help guide the chip. That might be what you are seeing.

 

[VicHobbyGuy]

After a post by VicHobbyGuy, I took another look at the Vever 7X lathes, they don't have a 2 speed transmission in them! (All or some, not sure). Learning again!
For those that have these lathes, what rpm would you be likely turning for 1.25 ss shaft? A ball park. I know, material dependant, etc. Using HSS, type of carbide?
I know, lots of variables. The general HSS tool bit idea of slow it down (rpm, 10, 20, etc.) does not seem to work as well here.
An idea, good, bad?

I don't own the Vevor 7x14 any more so I can't do any testing, and report back here- I'll leave that to @Chris Cramer, if he is willing. (I kept my 7x14 MicroMark lathe.) All the Vevor 7x12 and 7x14 lathes were made by RealBull and don't have a Hi-Lo transmission inside the headstock. The big majority of 7x lathes (Harbor Freight, Grizzly,BusyBee,Micromark, LittleMachineShop) are manufactured by Sieg and most of them have the 2-speed transmission. BTW, that two speed transmission is nothing like the back gear arrangement on an old Logan/SBend/Atlas, so put that out of your mind. . The 'Low' speed range is 0-1500 RPM. So even on low, there's not much torque under 300 RPM or so. (I upgraded my 7x14 from the stock brushed motor to a brushless motor with twice the 'nominal' power, which does have better low speed performance.)

 

[Chris Cramer]

The RPM of this 7 x14 550w mini lathe is 50 - 2500 RPM, and the torque of the motor is 3/4 HP. On some reviews I watched on this machine, they tested the RPM of the original 3 jaw chuck without any stock and measured 2800 RPM. I ordered and installed a four jaw chuck of the same diameter (100mm) but I'm still feeling it would be heavier than the original.
The machine doesn't have a multi speed transmission, it just has one set of pullies; but the control box offers variable speed to the motor.

 

[VicHobbyGuy]

The RPM of this 7 x14 550w mini lathe is 50 - 2500 RPM, and the torque of the motor is 3/4 HP.

Does your lathe have a tach (RPM display)?
If it doesn't, this handheld tach would be useful:
https://www.amazon.ca/gp/product/B004Q8L894/
I bought one a couple of years ago and it works well. For a while, I didn't have a tach on my 7x lathe, so I put masking tape around the speed control knob and 'calibrated' the control using the handheld tach. I did the same when I got a small milling machine.

 

[Chris Cramer]

Does your lathe have a tach (RPM display)?
If it doesn't, this handheld tach would be useful:
https://www.amazon.ca/gp/product/B004Q8L894/
I bought one a couple of years ago and it works well. For a while, I didn't have a tach on my 7x lathe, so I put masking tape around the speed control knob and 'calibrated' the control using the handheld tach. I did the same when I got a small milling machine.

That is a good simple solution to keep track of the RPM. The machine does not have any display. I was thinking about using a simple speedometer that works with a hall sensor and magnet, but they probably aren't designed to process the data fast enough for something that spins this fast.

 

[VicHobbyGuy]

That is a good simple solution to keep track of the RPM. The machine does not have any display. I was thinking about using a simple speedometer that works with a hall sensor and magnet, but they probably aren't designed to process the data fast enough for something that spins this fast.

The cheap Hall sensor tachs will work on a 7x lathe. I put one on my drill press when I re-powered it with a variable speed motor. But, for my tools - drill press, lathe or the mill, at my level of skill, the RPM numbers just help to get me into the right 'range'. So the markings around the speed knob work OK for me. +/- 75 RPM or so doesn't make a big difference for the work I do..

 

[Chris Cramer]

So the markings around the speed knob work OK for me.

That makes sense, as I measure the RPM with the tach I can mark the different positions of the knob as a faster way of setting the RPM. The occasions that I think it would be most important is when threading, and when turning the cross slide along with the auto feed, since the auto feed depends on the RPM of the spindle.

 

[Susquatch]

@Chris Cramer - in addition to figuring out your rpm, can you also estimate depth of cut and the feed rate?

 

[VicHobbyGuy]

The occasions that I think it would be most important is when threading, and when turning the swing along with the auto feed, since the auto feed depends on the RPM of the spindle.

For threading, for me it's just a case of "as slow as it will go and keep turning and cutting metal smoothly" So that is 'by feel', pretty much. I think I mentioned using slow feed change gears for turning, to slow down the travel/rev- it can help with cutting as with slower travel it's often easier to use a bit bigger DOC (depth of cut), and also improves the surface finish a bit.

 

[VicHobbyGuy]

@Chris Cramer - in addition to figuring out your rpm, can you also estimate depth of cut and the feed rate?

I can help here, if that's OK?
The stock change gears for normal turning are 20-80-20-80 which drive the leadscrew at 1/16 (20/80*20/80) the speed of the spindle.
With the metric 1.5mm leadscrew pitch on @Chris Cramer's machine, this will result in a sideways movement of the tool (feed) of (1.5/16)= .094 mm per revolution, or .0038"/rev .
This is the same as the feed rate with the 16TPI 'inch' leadscrew which is .0039"/rev - equivalent to a 256 TPI thread.

The cross slide dial is graduated, so once the backlash is taken up, that's a convenient way to measure DOC.

 

[VicHobbyGuy]

Here's a pic of the slow feed gears on my lathe - they reduce the feed from .0039"/rev to .0026"/rev.
The slower gear sequence is 20-80-15-90.

 

[Susquatch]

@VicHobbyGuy & @Chris Cramer

Thanks for that Vic - I assume it's Vic.

I'm a bit confused. Are you saying that Chris's standard feed rate is 4 thou? Or that this is what he used earlier?

Can he also choose other thread pitches to get higher feed rates? Say 128 to get 8 thou, 64 to get 16thou, etc.

Chris - I assume you can tell us what you were doing previously based on the info Vic provided above.

Or maybe, as Vic suggested earlier, I just don't understand.

 

[DavidR8]

@VicHobbyGuy & @Chris Cramer

Thanks for that Vic - I assume it's Vic.

It's John actually but he lives in Victoria hence the name.

 

[VicHobbyGuy]

Are you saying that Chris's standard feed rate is 4 thou? Or that this is what he used earlier?

Assuming @Chris Cramer is using the stock setup of the change gears, yes.

Can he also choose other thread pitches to get higher feed rates? Say 128 to get 8 thou, 64 to get 16thou, etc.

Sure, but I don't know why he would want to do that. Just replace the 80T gear attached to the end of the leadscrew with a gear with a smaller tooth count, and the leadscrew speed relative to the spindle will increase.
Increasing the feed would cause more problems in cutting hard materials with a 7x lathe, I think. You have selectable -via a lever- feed on your lathe? What feed rate do you usually use?

Or maybe, as Vic suggested earlier, I just don't understand.

So far, your report card comment would read "Student is willing to learn" Nothing wrong with that. "Coach-ability" is a very important quality! Thanks for taking the time to delve into this.

 

[Bandit]

I think part of the key to this, is the Vever lathe seems to have poor slower spindle speed operation and I need a think set change, to operate at much higher spindle speeds by myself, when I am used to the ability to turn much slower when machining difficult materials. And threading could be interesting also.