I'm nearing completion on this project , not a lot left now . All that's left is the nut to hold the sleeve in the bottom plate and the one for tightening the collet , plus I still need to drill/mill the index dimples in the collet holder . That completes the fixture , then I need to machine a means to hold the grinding wheel . Could go with a dedicated mandrel , could machine washers/plates to use one of the mandrels I already have . Snag "You can lead a dummy to facts but you can't make him think."
The collet tightening nut on my commercial fixture has a hex hole for an Allen wrench. The collet nut I made which accepts an insert to center an S&D drill bit shank has four radial slots that fit a dog-type wrench, as that was simpler to machine, although I have cut internal hexes by using a lathe as a shaper. The wrench handle is a V of 3/16" welding rod with the ends bent inward to fit holes in the OD of the wrench.
Since it's small I made it look nice to add to the samples I took to job interviews. At lunch today I was chatting with a retired HR manager and showed her some. She agreed that they were more convincing than anything I could write on a resume, since they were physical proof instead of questionable claims. Similar goodies got me into Segway.
1-1/4" is a common center hole size for surface and tool grinding wheels.