.

I've never yet had the need for one … but it's nice to know they are available.

MichaelG.

The only thing I have ever seen them used for is for machining commutators on old car and motorbike generators and starter motors. Many don't have centre drill hole in that end of the spindle for some reason. And others that do have a centre drill hole, the OD of the spindle and the commutator are not concentric with the centre hole. Something to do with the way they are made in a rapid-fire production process. I had a 2001 Honda starter motor armature that was like this.

So, you grip one end of the spindle in the headstock chuck and the other end in a revolving tailstock chuck and take a fine cut over the commutator segments if they need cleaning up and thus get them concentric with teh spindle where it fits into its bearing during normal service.

I think they used to be called an armature chuck once upon a long time ago.

Are they worth having? Yes if you recondition DC generators, electric motors (brush type), magnetos, starter motors etc.  Otherwise? I can't think of any other time I needed one. Usually you can drill a centre hole and use a tailstock centre, even if you then cut the end off and face it to get rid of the centre hole afterwards. Or turn up a bushing to fit over the end of a shaft, with a centre hole drilled in the bushing.  Much easier to use a revolving chuck though I suppose.

Edited By Hopper on 22/10/2016 13:04:24

Edited By Hopper on 22/10/2016 13:08:37

Made myself a revolving drill chuck, and have used it to hold small parts without a centre, or sometimes as a small running centre, in the Tailstock . Not a n absolute essential, but occasionally a very useful tool to have.

Howard