You may remember that I had a problem with the variable speed drive box on the chipmaster lathe at Scienceworks. I had resolved to strip out the internals of the variator and replace it with a shaft that went straight through the box ( thus making it the most expensive pillow block I have ever seen) and vary the spindle speed with a frequency inverter.. Yesterday, I decided to have another look at it before I gutted it. I pulled it apart, and measured the diameter of the six balls. ( See photo at the bottom of this page
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).There didn't seem to be any real wear marks on them, though you could feel a slightly different texture on the area where they contacted the drive and driven plates. Ther was no more than 3 tenths of a thou difference in diameter , between the working area and the part that didn't thoch the drive/ driven shafts.I dismantled the ball/shaft assembles and turned the balls upside down on the shafts,so the wear was on a different part of the balls. I put it all back together and test ran it. Better than it was, but no cigar. There were still speed ranges where it slipped, then suddenly sped up. As a last resort, I increased the preload that forces the balls against the input and output shaft discs. Another test run. Break out the champagne! It ran over the entire speed range smoothly, and didn't slip even when I put a fairly heavy cut on. We were told that a new variator would cost about A$6000 and the alternative ( a variable frequency inverter) was about a thousand dollars. The great thing about being retired is that you can take the time to do things the right way!