That looks a bit like the chuck mounting on my Sieg C6. It has three driving studs which are attached to the chuck backplate and are inserted through holes in the mounting flange on the spindle. There is a rotating plate behind that with bayonet-style holes which engage with the driving studs, and then held in place by nuts on the threaded end of the studs. Sounds more complicated than it is, harder to describe too. Mine is a 5" chuck and only has three drive studs, but i imagine the larger sizes would have more. The drive studs and the bolts holding the flange to the spindle all seem to be evenly spaced.

Don't know if that helps at all.

Geoff P

I had an Emco 8.6 that used a modified version of the Din mounting. Just the short taper and 3 threaded studs in the chuck, no drive stud needed. Fix with three loose nuts and washers from the back which for out ME size machines is adequate.

Its a very tight tolerance on the taper as you want it to be fully seated as the back of the chuck touches the rear flange, too little and it won't self ctr on the taper, too much and it will get stuck.

Hi Rainbows

My Heidenreich and Harbeck lathe has a Din 55027 size 6 spindle nose.

The taper and face dimensions are the same as a similar size Camlock spindle nose, the difference is there are no cams the chuck is bolted to the face. Note the dark (knurled) ring on the back face, it can be rotated a few degrees, this presents holes and slots that are milled in the ring, "keyholes" that allow the chuck fitted with posts that have a smaller diameter threaded section with a nut pass through the ring. the ring is then rotated capturing the nut. The nuts can then be tightened with a spanner.

The process is a little slower than rotating keylock cams, on the other hand it is extremely stiff. My lathe does not and never did have the driving stud, the 4 M12 studs are more than enough to hold the chuck fast on the taper and face. Far more securely than a Camlock.

For a 6 inch chuck surely 3 firmly tightened bolts would be fine.

A few images below that include measurements.

**LINK**

Regards
John

The 2 'little studs' are shown in the standard as counterbored holes (presumably to take cap head screws with a little clearance – I guess these would go through the obround slots in the bayonet ring to allow it to be held in place behind the spindle nose).  [edit – or maybe they limit rotation of bayonet disc].

Edited By David Jupp on 27/07/2016 14:04:33