Threaded spindle questions


Nov 19, 2013
Hello all,

I am fairly new to machining and metal work. I have always been interested in lathes of any kind. I have been a woodturner as a hobby for a long time now. I acquired and restored an old Logan metal lathe several years ago. I am slowly teaching myself how to properly run a metal lathe. I am getting more and more confident. I've been working on cutting threads and tapers lately.

In my wood turning experience, it has not been uncommon for me to want to make my own chuck, faceplates, adaptors and tapers. One thing I have noticed in trying to make things to fit threaded spindles, is that threaded chuck and face plates usually have two flats being the thread that assist in maintaining concentricity. One is immediately being the thread, parallel to the spindle. The other is a shoulder that is perpendicular to the spindle.

What I am looking for is any input on making any of the following items properly and maintaining concentricity. I am interested in making:

Threaded adaptors, to make chucks fit different machine threads.
Basic chucks and face plates.
Machine spindles( I have a hand operated rose engine lathe that I am planning to build.)

Most threaded spindles use a shoulder to maintain concentricity as the threads themselves will not do a proper job in that area. The shoulder on the spindle is a close fit to a recess in the chuck or faceplate. It is this close fit that actually maintains concentricity, not the threads, thus due care must be given when machining the shoulder on an adapter or the recess in a backplate so that concentricity can be maintained to a proper level of accuracy.