I have an ER40 chuck on a bib-bore 7 but the principle is the same.

The backplate screws on the spindle nose just like a standard chuck backplate.

There is an oversize register on the backplate that you then machine concentric and a very good fit (slightly tight) into the recess on the collet holder part.

Then bolt the holder part in place and you're good to go.

Buy a ball bearing collet closer to make it easier to get good clamping force.

Should not be a problem to fit a 5C chuck to the Myford, I have held spur gears in my 5C collets a number of times and they grip at the end.

Another alternative would be to get some soft jaws for your existing chuck that can be machined in-situe and give the best contricity of all the options, again that is how I hold larger spur gears. A slight step in the soft jaws make sit easy to eliminate any wobble that you can get when gripping by just the edge.

If you do go with ER then you will need to make a plug to go in teh back end so they close down parallel onto the spur gear

Edited By JasonB on 12/02/2020 07:30:20