bearing lock nut on ball screw, how to?

[replicapro]

I just finished turning down a 5/8 ball screw so I can put the bearings on for my Z axis. The lead screw im replacing has a threaded section above the bearings for a set of 2 nuts which are used to take up the slack and lock the bearings in tight.

My question is how do I make thread on the ball screw that are larger than the section I already turned dow, yet smaller than the ways already on the ball screw shaft. It seems like on the exsisting lead screw they had the threads for the lead screw the same as the threads for the lock down nuts, so if I were to reproduce that on the ball screw, I would need a set of nuts that have the same thread as the ball screw.

[HuFlungDung]

Can you make an accurate sketch of what it looked like, and how you are planning on changing it over?

I suspect that you should be turning to a shoulder on the ballscrew, maybe 3/8" to 1/2" diameter. That shoulder should serve as the abutment for the support bearings, and you really only need one locknut to tighten the bearing's inner race to this shoulder.

Generally, a nut with a jamnut is a poor way to preload a set of bearings, even on a simple machine, it is difficult to remove the backlash and assure that the faces of the nuts are not creating a bend in the shaft and a lack of a true running surface to push against the bearings with.

Better to use a single nut, and some appropriate custom machined spacers or shims to create the proper preload to eliminate backlash.