A collet chuck for the Unimat SL.

Another piece of tooling for my Unimat SL, this time a genuine Unimat collet chuck. This is used with seperate collets, which are individually sized, to hold milling cutters when the machine is set up as a milling machine, or bar when turning. The collets are ground and clamp the workpiece/cutter far more accurately and securely than a drill chuck or 3 jaw chuck. As they clamp over a larger area there is less chance of marking the surface of the part being held, unlike a 3 jaw chuck which holds the work in 3 relatively small areas.

I found this on Ebay, and managed to get it for the starting price as no-one else had bid on it, unusual as these are usually highly sought after. Must be the post Christmas slump...
Here it is mounted on the headstock;

With the clamping nut removed, showing the ground taper;

The clamping nut has an M20x1.5 thread.
Four collets were included, 3/16", 5mm, 6-7mm (which takes FC3 milling cutters), and a home-made collet which needs final finishing. The collets are of the obsolete E16 type, so only available secondhand although making your own is an option.

I'd read that the more modern ER16 collets will fit, so I bought a cheap 4-5mm one from an Ebay seller (£2.71, including postage, from Hong Kong apparently). On the left is an E16, on the right the cheapo ER16;

Note the larger face diameter of the ER16, and the release groove.
It works in the holder, here it is holding a 5mm drill, note though how the front of the collet is recessed behind the clamping nut which sits further out from the chuck body;

And for comparison here's the same drill mounted in the 5mm E16 collet;

 

So it looks like ER16s can be used, and I'll probably get a few more, but I'll be on the lookout for secondhand E16s. I should point out that this chuck hasn't been used in anger yet.

Paul.