I've done the ends of ball screws 5 times now using this method.
Get the screw running in the lathe as true as you can using any of the suggested methods. If it is a long screw make a plug or rig a simple chuuck for the back end of the spindle. Drill the ball screw 3/8" X 1-1/2", (drill, don't bother reaming). Machine a piece of stock large enogh for the end you need with a 3/8" tongue. Test fit it into the screw. You want a slightly sloppy fit. If the fit is tight, file a flat on the tongue. Coat the parts with silver solder flux, assemble and silver solder with the lathe running slowly.
I put the tail stock up to the end because if you have too much flux in there the end will blow right out. After it cools machine the end you need making certain the screw is still running true.
To get a true running rolled ball screw, I use a C5 collet that fits snugly. 5/8" is too big. You can also make a fairly thin walled tube from aluminum that fits snugly and indicate on that.
Jerry |