Making a W12 wax chuck

In order to hold various parts, such as the barrel and balance wheel, for machining, I wanted a wax chuck. I briefly considered making a brass copy of a W12 arbor but decided that was going to be a lot of work and difficult to get accurate. After all, part of the idea of the wax chuck is that I can swap the part between the Schaublin 70 lathe and the Aciera F1 mill without losing concentricity through any remounting.

Eventually I decided to take a steel W12 arbor blank and make a threaded spigot on the end onto which a brass boss could be screwed. This has the benefit that the brass can easily be replaced if necessary.

I wanted to be able to make the thread on the spigot on the lathe, so I needed a way to hold a W12 collet on the Hardinge, which takes 5C collets. In one of the job lots I had bought there was a sleeve, parallel sided on the outside and machined inside with a parallel bore and a short taper to fit a W12 collet, complete with a nut with a buttress thread. I turned this sleeve down to 3/4″, the largest collet that I have for the Aciera F3 and a size I have for the Hardinge lathe, and tapped a small hole for a grub screw with a spigot turned on its end to fit in the locating slot on the W12 collets.

The arbor in the sleeve:


And without:


And next to two pieces of 5/8″ brass bar, faced and tapped to fit. I have used thread lock in order to hold the brass securely in place, which may in turn require flats to be milled on the brass for its removal.


The wax chuck was then mounted in the Schaublin 70, faced, grooved and turned down to the diameter of the barrel.