Lathe Bed Wear

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earthbound

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Hi folks, I'm getting to the point of practice where the wear in my bed is starting to hinder my progress. I'm always offsetting my tailstock on parts between 6-12 inches and I get a bad taper in all the parts I turn close to the headstock. I'd like to have the bed reground but every shop in Chicago that I've contacted has flat out rejected my inquiry so I have a few questions. 1) Are the ways of this machine made of cast iron? 2) Is cast iron more problematic to deal with resulting in perpetual rejections? 3) Would a properly executed flycutting job on a mill be a possibility for the tops of the ways and an endmill to take care of the sides? I'm really at a loss because I'm really in love with this machine. I've invested a lot of money finding nicer components and I'd hate like heck to simply part it out or get rid of it.
 
Hello earthbound. I see no one has replied to you yet so let me get the ball rolling. If you would advise the make and model of your lathe it would help.

1) Re the ways, if we assume your lathe is an Atlas or equivalent flat bed lathe then the Atlas MOLO advises:
‘Lathe beds are made from selected close-grained semi-steel iron castings. The entire bed, comprising the cross ribs, ways and base is made in one piece’.

http://vintagemachinery.org/pubs/detail.aspx?id=13891

3) Re flycutting the ways. Wow that seems a bit drastic. The Atlas MOLO advises that the bed is first rough milled, then seasoned, then finished milled and then the ways are finish ground. I suggest there is a very real possibility you would scrap your lathe if you sent the bed away for milling/flycutting.

Have you thought about setting up your lathe from scratch to eliminate tapered turning? So, level the lathe bench or stand and shim the bed feet so that the lathe bed is not twisted when it is bolted down.

http://vintagemachinery.org/pubs/detail.aspx?id=7401

Is the tailstock sloppy running between the ways. If it is not a snug fit between the ways then the position of any centre mounted in the tailstock ram will not be repeatable. You may be able to shim out any free movement between the tailstock and the ways.

If you are getting a bad taper when turning close to the headstock it could be that your tailstock is misaligned. For taper-free turning using the tailstock centre the tailstock centre must accurately match the centre-line of the lathe spindle. Some people recommend cutting a test bar but I have found that using two arbours (one in the tailstock and one in the lathe headstock spindle) in conjunction with a dial gauge is fine. And the 2 plain ends form an infinitely adjustable test bar.

Hope this helps, atb, Ian

Arbours MT2 x plain ends.JPG
 
That' what I use. Stub arbors from Busy Bee are only about $10.
 
Ian, the taper near the headstock that I'm referring to is when I'm turning something maybe an inch or less without a tailstock. This inclines me to believe that its really the bed that's the issue, specifically the outer faces of the ways. The tailstock sits extremely snug between the ways but there's a visible erosion on the tops of the ways where the tailstock rides. It's probably about 10 thou deep or more in some spaces. I think since I tend to turn smaller parts that the outer sides of the ways are the most important issue to address here. Droop wouldn't make a 5 thousands taper on a half inch thick one inch long part, but the outer surface of ways sure could cause that. Thoughts?

Andrew
 
Seems to me thats a pretty steep taper to come from wear alone. Might check some other things too, bed alignment with the headstock, your chuck, bed level, etc.
 
I could surely check that too. It's really only like the last 1/4 inch or so that gets this kind of taper. The headstock fits extremely snug with the inside of the ways. Im not sure I could cock it one way or another if I had to... I can certain try though. I'll have to check when it's above, 10 degrees F because I can't stand working for long periods of time in weather like that. I really appreciate all the replies so far. Has anyone had success regrinding an Atlas bed?
 
Earthbound (you should set up your Signature),

Yes, there have been some few cases of reports of people having their Atlas beds reground. However, it is quite an expensive proposition. It sounds from your description that your be is in fact excessively worn. But I would suggest that you find a replacement bed instead. The few people around (mostly found on eBay) who sell used Atlas parts regularly never bother with the beds it seems. Probably due to shipping costs. But that does mean that beds are around and if you can find a good one, it shouldn't be expensive except for shipping if you cannot go and pick it up. Unlike a V-bed lathe, it is relatively easy to accurately assess an Atlas bed for wear. Measure the thickness of the front and rear ways near the front and rear edges of each, and measure the width of each. Do this right at or underneath the headstock and about every two or three inches all the way to the tailstock end. Nominal thickness is 0.375" on the early beds and 0.500" on the late ones. The actual original thickness from bed to bed varies maybe +/- 0.005" but the thickness of any individual bed originally varies only maybe +/- 0.0005".

Note that the 9" . 10" and early 12" beds were made from the same castings and would be interchangeable except for the drilled or drilled and tapped holes for mounting the legs and maybe the headstocks and either FWD-REV box or left lead screw bearing housing So one could use a 10" bed on a 12" or vice versa I think. But it would be extra work.
 
never worked with Atlas lathes, so no expert by any means. However, one possibility comes to mind re: taper close to the headstock. Is your headstock bolted to the ways? If so, perhaps someone removed it previously and did not properly level it when rebolted.

I recently was reading a lathe rebuilding thread and the author mentioned it is critical than the headstock be properly torqued on all four corners to be square with the centerline of the lathe.

Seems to me the taper you mention is so severe that the spindle must be canted off the center line, or improperly ground- causing the work to be non concentric.


Something to check out, maybe.

Glenn
 
Thanks for the replies gentlemen. I'm going to chuck up some drill rod later today and throw an indicator on it to see if you what it looks like down the length of the bed. I have some 7/8" tgp drill rod that should be straight enough for an inspection like that. And to answer your question Glenn, yes it's bolted to the ways and there's a real possibility it's been removed. The machine is probably 60-70 years old and its been used heavily.

Andrew
 
Hello again Andrew. Interesting further info there.

Firstly focusing on 5 thou taper on a 1/2 inch diameter part, 1 inch long. The longitudinal movement of your cutting tool is controlled by the carriage, which should be snugged up to the ways by adjusting the carriage gib. A bit of trig suggests that to produce a 5 thou taper would require the carriage (and cutting tool) to drop or rise by 35 thou from nominal. This seems most unlikely, especially over a length of 1 inch.

So perhaps the axis of the headstock and spindle is not parallel with the ways of the bed. A 5 thou diametral taper over 1 inch (2.5 thou on radius) implies an angular misalignment of the headstock of 0.143 degrees. I am not sure there is much or even any adjustment on the headstock position, but 2 things to check would be cleanliness of the mating surfaces and internal/external corner clearance - the internal corners of the headstock should be smaller than the external corners of the ways.

Turning to wear on the ways. Normally the tailstock runs on the 2 inboard sections and inside faces of the 2 ways; and the carriage runs on the 2 outboard sections and outside faces of the 2 ways. There shouldn't really be any significant way-wear on the areas that the tailstock runs on, as the tailstock is only moved under no load. If the erosion you mention is actually from corrosion it might be possible to effect a repair of corrosion pits with plastic metal, i.e. clean and fill the pits up to the original surface.

Regards, Ian
 
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