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Where to get good used mill

RobinHood said:
I have heard about these oddball dials before - especially on older off shore machines.

Here is my best guess as to how they arrive at 110 divisions: the lead screw they used is likely metric. Something like a TR40x14(P7)LH. What that means is the nominal OD of the trapezoidal thread is 40mm. (Probably not that big of an OD, but you get the idea). It has a lead of 14mm per revolution, with a thread pitch of 7mm. That means it is a two start screw (14/7=2).

How does that give us 110 divisions on the dial? Well, 14mm is about 13.97mm. 13.97mm = 0.55” per turn. 0.55” / 110 = 0.005” for each division —> as is stamped on your dial. Hence the odd ball number of graduations.
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I managed to hobble out to the shop this afternoon on my sprained ankle. My plan was to try and measure the lead screw pitch on the x & y axis so I could make a proper metric scale for it. I had no idea what kind of surprise laid in wait for me.

I discovered that it's actually an SAE 10tpi screw! Ten full turns equals 1 inch on both axis

That will make the job a lot easier. All I need is new SAE dials or at least new scales. I doubt they are hard to find but if so, I can always make new ones or even simply turn down and remark the existing ones. SAE dials will also probably increase the sale value a bit.

In fact, maybe I'll even try to make or fit some friction scales so I can set zero.

I confess that I am more than a bit embarrassed to have to admit to you guys that I never looked at this before. I did some quick measurements when I first got it, and then abandoned all use of the dials or counting turns because it was so whacky. I just used it by marking and measuring parts and didn't use the dials for anything at all. If I had known then that it was actually a 10 tpi screw, I would have fixed the scales many years ago.

But now I am more curious than ever about how it got those 11 graduation dials! What a weird mystery.......
 
@Susquatch : those dials are from a machine custom built for a member of the Rock Band "Spinal Tap"....Most dials go to 10 but "Spinal Tap" dials: they go to 11...ya mate....11 ...hahahahaha
 
Brent H said:
@Susquatch : those dials are from a machine custom built for a member of the Rock Band "Spinal Tap"....Most dials go to 10 but "Spinal Tap" dials: they go to 11...ya mate....11 ...hahahahaha
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KolinFous said:
I think this is a limited edition
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It is such a quandary. My brain hurts. Except for the 005 marking on the inside, the opposing marks look so totally oem. Yet, so out of place.

It's reminiscent of the common counting mistake that so many people make by counting edges instead of the spaces between them. For 10 spaces (increments) you have 11 edges. The zero edge is the first edge, the first space is a 1, and there is no zero space.

Then there is the issue of number bases. Most of us think we live in a mostly decimal world. But in reality, we live in a mostly binary world. To help address orders of magnitude and reduce paper, some of us learned to use octal, decimal, and hexadecimal. But 11? Where in heck did that come from. The Kings foot was 12 inches. Maybe his brothers foot was 11......

Part of me wants to think it's just a huge mistake that somehow made it into production and onto the shipping truck before anybody could stop it. I probably paid more for it well used than what they sold it for off the truck!
 
Even badly worn out screws == big deal. Measure the screw length, go to eBay or Aliexpress and buy a new screw for like 200, max 300 CAD with a brand new nut. Main problem will be that it may not match your dials... not a big deal, China sells BP clone metric dials for around 20 a peace. I am talking about grade7 ball screws. For like 30 CAD extra you can get 2nd ball nut and bring backlash in your repaired machine to around 1 thou. That is WAY better then factory.

With rolled balls screws cheap these days, why would anyone bother with ACME as much - I guess main problem could be ball screws do not have a lot of friction... but you can just tighten the ways.

For under 3000 a working machine was a good deal. Unless it shows clear abuse - like table used as an anvil. Or holes made as gun range target.

Also why such a big worry about backlash - in manual machine this is standard - I only worry about it on a lathe when parting - you do not want it too loose.
 
YYCHM said:
Did you go have a look at it?
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Not really. I could see that the bed was chewed up and the guy wasn't forthcoming with info. It gave me a bad feeling. In any event, my real reason for bailing was my wife. She has always wanted an industrial sewing machine to do upholstry, leather, and heavy canvass. She found one so I gave up my cash. She is a dream come true that any fellow half my age would grab in a heart beat. It was an easy choice. Life has many turns and things usually happen for reasons.

I'll keep looking and in the meantime I'll fix up and use my existing machine. That will make it more usable and also easier to sell.

It's quite the story. See my next post......
 
Tom Kitta said:
Even badly worn out screws == big deal. Measure the screw length, go to eBay or Aliexpress and buy a new screw for like 200, max 300 CAD with a brand new nut. Main problem will be that it may not match your dials... not a big deal, China sells BP clone metric dials for around 20 a peace. I am talking about grade7 ball screws. For like 30 CAD extra you can get 2nd ball nut and bring backlash in your repaired machine to around 1 thou. That is WAY better then factory.

With rolled balls screws cheap these days, why would anyone bother with ACME as much - I guess main problem could be ball screws do not have a lot of friction... but you can just tighten the ways.

For under 3000 a working machine was a good deal. Unless it shows clear abuse - like table used as an anvil. Or holes made as gun range target.

Also why such a big worry about backlash - in manual machine this is standard - I only worry about it on a lathe when parting - you do not want it too loose.
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I'm not really fussed about backlash. I was only observing that 70 thou is more than 1/2 of a 10 tpi thread and therefore unlikely. I'm no expert though. I just can't see how that can happen.

My lathe has excellent backlash but nowhere near zero. And for what it's worth, I find that parting is always a challenge even with low backlash. Maybe I'll master good parting before I die. Lord knows I do a lot of it because I don't have a metal cutting bandsaw. I do what I can the normal way and when that fails, I flip the tool upside down and cut in reverse. This almost always works but can be noisy.

So time to fess up. I measured my screw wrong in an earlier post. (insert red face here) I made the classic mistake of not counting turns properly.

So, it turns out that the 11 is close to correct. My screw is actually a 7/8-9 regular 60 degree V thread.

Maybe it was metric at one time, or maybe not. About all I can guess at this time is that the original screws were worn out or metric and somebody swapped them out for a standard 7/8-9 threaded rod with 60 degree threads.

When I get time, I plan to remove the table completely and figure out what it takes to install ACME 10 tpi lead screws and nuts or even "Grade 7 ball screws and nuts" as per your suggestion (have to figure out what that is all about and if it makes sense for my machine) along with properly calibrated handles.

My appologies to everyone for my goofy error and the wild goose chase.
 

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I think the mill has sold......


Nope - Still there.....its listed as "Bridgeport Mill" so if you were looking for a milling machine it would not pop up ......might buy someone some time...
 
Brent H said:
I think the mill has sold......


Nope - Still there.....its listed as "Bridgeport Mill" so if you were looking for a milling machine it would not pop up ......might buy someone some time...
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Holy Cow. You guys are sure right about how fast these things go. I never even got a look at it on Kijiji let alone in person. Too busy farming. If I do get the chance I might have to go into debt though.......
 
Susquatch said:
I'm not really fussed about backlash. I was only observing that 70 thou is more than 1/2 of a 10 tpi thread and therefore unlikely. I'm no expert though. I just can't see how that can happen.

My lathe has excellent backlash but nowhere near zero. And for what it's worth, I find that parting is always a challenge even with low backlash.
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yeah, imo how much backlash there is (with in reason, see photo) doesn't effect most operations. There has to be some in a tradition screw, so if there is some how much there is usually doesn't matter. e.g. aggreseive climb milling will be problem at 50 tho backlash, as it will at 15.

Lots of backlash will be in an area of high wear. Where it matters is when you're measuring or transitioning over a long distances that goes from areas with different amounts of backlash- i.e. two holes on the mill 12" apart. Time to get out the toolmakers buttons.

Having said that, where backlash does really matter is in sizing up a machine. Excessive backlash is wear, and if there is excessive wear in one part of a machine, dollars to donuts there will be lots of wear through out.

Fb1MP1N.jpg
 
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Mcgyver said:
yeah, imo how much backlash there is (with in reason, see photo) doesn't effect most operations. ........ Time to get out the toolmakers buttons.
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Nice summary of the wear backlash issue. And what a great photo! Thanks for that.

So, I am a hobbiest and no pro. So maybe I don't need them or don't even need to care, but you tickled my curiosity nerve. Besides, i love learning new things. What is a tool makers button and how are they used?
 
thanks.....imo being a hobbyist isn't dissadvantage, I'm a hobbyist as well.... only difference is someone told me about toolmakers buttons :). its a ground cylinder of precise dimensions. Say you need two holes 4" apart and and each tool button is .25 diameter. drill tap two holes around 4" apart and mount the buttons. Put a 3.75" gauge block stack between the buttons and tighen them. Indicate the botton, drill and bore with boring head. Do that for each button and you now holes 4" apart. Its pretty much jig borer accuracy with simple equipment. The shots below are me making holes to perfectly line up with existing dowel pins. When the DRO isn't good enough :).

I apologize for straying, but since you're the OP I'll risk the torpedoes....here's the process. Making an adapter for a lathe two speed gear box - part of upcoming article in HSM

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fits perfectly!

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Mcgyver said:
thanks.....imo being a hobbyist isn't dissadvantage, I'm a hobbyist as well.... Fits perfectly!
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I didn't actually follow all that in detail, but I get the general idea. When measuring is too difficult, make a precision block (or stack of blocks) and use buttons (pins) as precision locations instead. Very cool. Thxs for explaining.
 
you are welcome. its a fairly elegant in its simplicity - the buttons are just a way to reference an axis. That you are using gauge blocks not the feedscrew means its condition or accuracy doesn't matter, . I was a using a coaxial indicator, it could have improved that slightly with a 10ths DTI, but it proved good enough
 
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