Terry,
Just make your own. I've been making my own 2pc collets for years. As a toolmaker, I just couldn't find any OEM collets that ran true enough. With your attention to detail, this will be a breeze.
Start with the ID features of the nut, but turn out blanks first. Turn the OD above the points of the finished hex and face the shaft end. Turn out as many as you want. Then, bore out a soft collet matching the OD of the nut blank and do one operation at a time to all your blanks until you have the ID features done. Set them aside.
Start the same process with the collets, turning the OD and facing the shaft end of the collet. Then, bore out a soft collet matching that OD. Again, one operation at a time, turn your pilot diameter and step, drill and tap for the crank threads and bore the ID for the flex shaft. This should ensure almost perfect runout between the mounting face and the flexshaft. Set them aside.
Turn out a stub fixture, starting with the mounting end, matching a 5C collet of your choice. Mount into that collet, bore it for your pilot and drill and tap it for a threaded stud matching the crank threads. Do not remove from spindle until collets are finished. You can then, again, one operation at a time, turn out the OD features of the collet, matching the threads to the tapped threads of the nut. This should ensure near perfect runout between the ID and OD features.
Next, mount the fixture in a 5C indexing fixture. Mill the hex on both collet and nut, locking a nut onto each collet as you go. Tool pressure should only serve to tighten the nut onto the collet as you mill the flats. Once the hex is finished on each collet/net pair, remove the nuts and cut slits in the taper area of the collets.
Deburr and enjoy near zero runout. Don't forget to sweep up.
You might also consider turning out a stub fixture, and, using your flywheel collet, turn the mounting face of your flywheel(s). Once you lock the flywheel onto the fixture stub, you can remove the nut and it should stay affixed. You'd be surprised at how far out this face can be.
This sounds like a lot of work, but it's really not. If your churn out a dozen or so units, you should be good for quite a while. IF you hang onto this tooling, collets and fixtures, you will be that much ahead if you ever need to make more.
I have found 17-4ss to be a very adequate material for these.
Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC
