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How to calculate a minor diameter for a ball screw?

Sparks51

Plastic
Joined
Oct 27, 2014
Location
Boise, Idaho
Hello Gents,
Can someone please explain how to calculate the minor diameter of a ball screw?
I need to make an adaptor for the ball assembly to slide onto so I can turn it around and reinstall it onto the ball screw. The manufacturer put it on backwards!
I've look around a lot but haven't found anything specific to a ball screw!
Thanks very much!
Tom
 
You can measure the OD, then measure the depth of the groove from the OD, double that and subtract from the OD. Yes a depth mic with a flat end wont give you a true reading but you can estimate a small addition. Or you can drop a smaller rod or pin gauge into the groove and measure down to that.
 
Calipers on the root and about 10-20 thou smaller will work just fine if your ID/OD runout is zero.
Note here that since the calipers will not be 90 to the shaft the reading is bigger than actual.
You can get away with lots more slop than this before you will lose your balls.
It is easy, don't overthink it.
 
Last edited:
You can measure the OD, then measure the depth of the groove from the OD, double that and subtract from the OD. Yes a depth mic with a flat end wont give you a true reading but you can estimate a small addition. Or you can drop a smaller rod or pin gauge into the groove and measure down to that.

That probably works for most simple stuff but people should know that a lot of ballscrews are not simple grooves. There's several shapes but a 'gothic arch' is pretty common. The balls don't actually run on the bottom.
 








 
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