How much way wear is too much?

Is the bed of the Chipmaster ONE PIECE with the stand? If the bed is screwed to the stand,shims could be placed under the foot of the bed at the tailstock end. I have had to do this on my 16" lathe,which has a 1/4" thick welded steel stand. I could not get the bed straight enough by just adjusting the pads on the floor. The rigid stand was too strong. I loosened the bolts at the end of the bed and added shims until the lathe was level,and turned true cylinders.

I haven't used a Chipmaster,so am asking the question.
 
I would respectfully differ with those of the opinion that the bed simply cannot be twisted. That's nonsense. It might appear and seem like it would be impossible, but all metals have properties that make them stronger in one direction than another, and machine designers take these properties into account when designing a machine. But there are always compromises. And metals change as they age. Green cast iron, in ingot form, is totally unsuitable for anything requiring rigidity, so of course, subsequent processes change the properties to improve things. But there is absolutely no way to make any metal totally stable. Even special metals that are used for measurement standards are kept in special environments to compensate for their instability, as insignificant as it is. A piece of cast iron, properly designed, is cast in the best shape thought possible to compensate for its far less than perfect stability. After casting, it is processed with various stress relieving heat treatments. Then it is rough machined. Again it is heat treated. Why? Again to try and improve its stability. Then it is semi-finish machined. Likely again heat treated. Then some machines are induction hardened on the ways. And machined further. There is no way that the end product is totally relaxed and stress free. What that means is that in time, it WILL move. That's why all the instructions come from the factory regarding leveling and mounting of machines. They are almost alive, and need to be restrained/constrained in the final shape, the same way they were held in the machinery that did the final machining, whether grinding or whatever.

I realize that the theory of the three point mount is to minimize any distortion from improper mounting, and it does make things more forgiving, but you are fooling yourself if you think the metallurgy of cast iron has developed enough to create a piece of machinery that stays as straight as manufactured. Just because the bed is a complex webbing made to look ultra stiff, trust me....it still moves. Time will get to it.
 
Indeed, time will get to it.

After all, that piece of solid iron at which you are looking is mostly empty of any atomic particles at all. Stability is a function of change over time. Less change and more time are the things we call stable.
 
I had levelled my lathe, and followed the manual to the letter - hence why I can't see how the bed would be twisted. I also know how well the previous owner looked after it and that he had it levelled since buying it new. The only chance it would have had to attain a permanent twist would have been in the 3 weeks from when the lathe was moved from the owners place, to the warehouse, and then to my garage. Given the rigidity of the bed, I think it would take a longer time to permanently twist the bed. Even if the lathe is slightly un-even, it's mounted on 3 feet which prevents twisting. I am unaware of anyone that has needed to adjust Chipmaster headstock since there are adjustment bolts under the headstock that are set from factory and from all reports, they are very accurately set.

I am still working on the electrics at the moment and when done, I will do a test cut and measure. Despite Colchester's best efforts and it's caring previous owner, I guess it could have a twist however unlikely it might seem. As they say, the proof is in the pudding and it's impossible to say with certainty that it is perfect until I cut with it and measure .



Paul.
 
Look at it this way too, Paul. It has 3 feet to allow twisting, too. The designers hoped, in this case, that it wouldn't be left with one foot up in the air out of 4 and that uneven weight distribution cause a more or less permanent distortion to occur. It's well known that a 3 point suspension will let things stay pretty much as straight and flat as they can be, but that's no guaranty that it won't/can't twist of its own built in stresses.

But you're right. The proof is in the cut. You can almost always find a more accurate level and see a little closer where it is, and there has to be practical limits on how close you can get it. But remember, it's not all about level; it's about getting it the same in all planes. On a rolling ship, the machinery is not at level very often, or for very long, yet they are set up with precision and are able to do precise work.
 
In my classes I teach that the use of 3 points is also a "Lost Art" as is "Hand-Scraping". I was looking at a Sheldon lathe that was mounted in the conventional way and after you posted the picture, I now see you were right. I was wrong. Hardinge also mounts its lathes on 3 points, Sip and Moore Jig Bores use 3 points too. Surface plates are mounted on 3 points to eliminate the chance of twist. When I set a mill table on horses when I scrape it I put it on 3 points or the scientific name is Kinematic Mount Principal so the table doesn't twist.
Merry Christmas everyone.
 
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