It may be an indicator to centre work?

Howard

It's a cheap homemade centring tool. Usually there is a fixed bar with a dimple in in which the pointed end inside the ring rests. The sharp end outside the end rests in a dimple in the work. As long as the fixed bar maintains the short rod in contact with the work, then as the work rotates, the out of centre amount is magnified by the long length which describes a circle in free space. Adjustment of the work can then be made until the long end remains stationary at which point the work is centered.

Somewhere I have a book with a drawing for it, but can't lay my hands on it at the moment.

Peter G. Shaw

Well you lot beat me too it!

Neil

What do you suppose that ring with the 4 square bosses is made from? Commercial casting or kit? Or cut from some extruded section etc the maker found lying around?

It's a cool old piece of kit from back when dial indicators were a luxury item in the home shop. I mightbhave to make one.

Rose joint….

Lump of rubber. Long wire(knitting needle).. continuously adjustable ratio…..

The device can only be used with the small end toward the workpiece as it has to be held between the internal point and the centre mark. The long end amplifies the movement in the same way as a lever indicator (here) making it easier to see the error.

Brian G

Ok I have totally misinterpreted the replies above, I was under the impression that a rod with a centre drilled into its rear and a point on the other end was held in the centre punch mark, and held with the tailstock, this tool then clamps to the rod and draws the circle in the air.

Thanks for the link to the website.