Lathe Bed Restoration

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earthbound

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Hello folks,
I've found a lot of good information on this forum so I though't I'd pick the brains of the experienced machinists here about restoring the bed of my lathe. I have an Atlas 12 inch lathe, and like many who own one, it's seen better days. I've done a lot of work on the thing (and had a blast doing so) and I'm having trying to weigh my options with refinishing the bed. For those of you who aren't familiar with the Atlas lathes, they have flat ways instead of the inverted v ways and this seems like a simple enough thing to fix up. Would it be worth having a machine shop surface grind these? Or heck, maybe even fly cut the ways and I'll take a stab at scraping them after? Is scraping then flaking something very hard to do? I've never tried to scrape metal but I've been working with wooodworking hand tools for about a decade and a half now and I have a decent touch with this sort of thing. I realize I'd need access to a master surface of an appropriate size. Has anyone ever reconditioned an Atlas lathe bed that turned out really good? Thanks for the input!

Drew
 
First, welcome to the forum.

Please define how worn out it really is. Report back with real numbers. If you want to find out how to do that, and how to do scraping, read Machine Tool Reconditioning:
http://www.hobby-machinist.com/threads/connelly-on-machine-tool-reconditioning.41802/
it is a free download in our files section, around 500 pages or around $100 to buy in hardcover. Restoring a lathe by scraping is in no way a trivial project. Just learning to scrape well enough and understanding how to rework the geometry of the lathe so you can start the project will take considerable time and effort. I am not trying to scare you off, scraping is a great way to get excellent results in restoring a lathe. It might take at least 100 hours for a competent scraper hand to do the job, probably way more for a beginner. If you try to cut corners the project will never come out correctly and will probably be sold disassembled, from what I have often seen.

The flat ways do not make the job much easier, and the other surfaces of the lathe should be made flat, parallel, and square, with the proper geometry, as well. Intuition will lead you down the wrong paths.

Typical machine shops cannot handle grinding lathe beds. It takes a large grinder, in excellent condition, and a skilled machinist who has done lots of that work. Few shops will touch it, and it is expensive. Milling is not accurate enough, and considerable scraping would still be required afterwards.
Again, not trying to scare you off, just a reality check. The only quick and easy way to get a reconditioned lathe is to buy one in nice shape and then sell (or keep) what you have now.

Well worn lathes do lots of very nice work. That is why I asked for numbers on how bad it really is. Machinists make accurate parts, the lathe is just a tool.
 
My thoughts, and I'm no expert but I also have a lathe with flat ways (Myford ML7) which could use a little work so I have been giving it some thought with a view to a mid life spruce up of my 57 year old lathe.

While the top horizontal surfaces of the ways are the most obvious and visible, they are the least important. Any wear here will cause the tool to rise and fall which would result in only a fraction of the wear's difference in the diameter of the work being turned.
Any wear on the vertical guide surface however will cause the tool to move towards and away from the work resulting in a change in diameter equal to twice the wear.

As an example (in the extreme to demonstrate):
For wear on the vertical guide surfaces of the ways:
D2 = D1 + (2 x Tool Horizontal Movement) i.e. if the original diameter is 25mm and the tool moves 1mm back then the new diameter is 27mm

For the same wear on top horizontal surface of the ways:
D2 = Sqrt( D1^2 + (2 x Tool Vertical Movement)^2) i.e. if the original diameter is 25mm and the tool moves 1mm down then the new diameter is 25.08mm

So my thought is to concentrate on the vertical surfaces of the ways. This wear also causes my problem that when the saddle gib is adjusted to be nice and firm at the chuck end of the bed it binds up as you move to the tailstock end, so you end up adjusting it for the unworn tailstock end and living with it being looser than ideal at the chuck end. To fix this I need to remove some material from the width of the way at the tailstock end to bring it in line with the narrowest (most worn) area's width.

I'm not familiar with the Atlas, but when the Myford was manufactured all four vertical surfaces of the ways were machined, however on mine only two are used for guiding the saddle (only the front way). The two inner vertical surface are used for guiding the tailstock. So the back surface of the back way is untouched and a virgin reference surface. Some lathes are 'wide guide' (including the later model ML7s) and use the two outer ways to guide the saddle so it would be one of the inner vertical way surfaces that was the best reference surface.

Figure out what is your least worn surface and measure everything with reference to that surface to determine how much material you would need to remove to bring then all back to straight and parallel. I have mic'ed mine and I would need to take a maximum of 0.05mm off each side of the front way.

In my case I'm considering following a method I have read about where a jig is made up to run on the reference surface and grind the worn vertical surfaces back to parallel - I'm not looking for perfect, but it should be able to make an improvement (and there is no way I can justify spending the sort of money it would take for a professional regrind). Still in the pondering stage so not fully committed to this idea yet.
 
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Drew,

There's bound to be grinding shops in the Chicago area that can surface grind the top of the ways for you. And probable touch up the sides too, without getting too carried away. There's a couple of machinery rebuilders west of you in Rockford, but I doubt they would touch it without you paying the price of a new lathe.
I guess the question is, how much are you willing to spend on reconditioning your lathe?
If the wear is minimal, less than .005", scraping the bed might be the way to go. You will need a fairly large surface plate and or straight edge to start the project off.
 
Gents, I measured a .008 dip on the ways... That seems like a lot in my novice opinion. I have to measure the difference in the width of the ways. I can see how that gib riding on the outer vertical surface can act like a taper attachment. Ive found myself offsetting my tailstock frequently mid project depending on how far I am from the headstock.
 
Myford used to say more than 0.005" variation in way thickness or 0.003" in way width was time for a regrind - back when the used to offer a factory regrind service.

upload_2016-7-27_8-12-22.png
From the Myford guide "Pre-owned Lathes - A Guide to Inspecting before you Buy", Sept 2010.
 
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Looks like I may contact a shop to grind it and then I'll try scraping it myself. Obviously id practice scraping something like a steel plate first. Has anyone ever made a home made straight edge? Is it dumb to try to scrape a face of an I-beam with a master reference surface? It seems like that's all a camelback edge really is. An iron or steel face with a structural spine.
 
There is no point of scraping it after it was ground, that is good enough, don't even flake it just something to collect direct. Scraping is a art if you don't know how don't even attempt it on something like that . I did machine repair for 25 years and plenty of scraping, on thread grinders. In order to make a straight edge you have to use cast iron steel is to un stable, it will change from the heat of your hand when you are scraping it in to a granite block.
 
Was just going to say the same thing - if you get it professionally ground you wouldn't need to scrape the bed. I doubt it would of been when originally manufactured.

You may need to scrape the saddle to make good contact with the newly ground bed - but ideally you would get the contact surfaces of the saddle reground at the same time so you shouldn't need much scraping.
 
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