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We were doing repair work on one of our machines which required the removal of both ball screws. We carefully cleaned them and inspected them for wear and they looked in good shape. But when they were spun in an engine lathe to test for smooth operation, we found them to be bent between 0.004" and 0.006". One is 60" long and the other is 78" long, they are both 1.500" diameter. Can they be straightened or do they need replacing?
Relax, It is not unusual for ball screws of the length and diameter you describe not to be perfectly straight. Some ballscrews, especially those over 8 - 10 feet in length and with a relatively small diameter can be over 0.100" out of straightness. What really matters with errors like this is that it is a gradual and naturally occurring curve caused by stresses within the material, that the diameter to length ratio allows for the ball nut and support bearings to compensate without overloading, and the ball screw is installed correctly. Sometimes trying to straighten a ballscrew with a stress related curve can add kinks detrimental to efficient operation and should be avoided.