I'm hoping it'll be fun, although until I read the collet thread I hadn't thought of doing this - I was just going to buy a small router or die grinder to use, so this is yet more work!

Robin wrote (in the other thread I was clogging up with this stuff)
Hi Jeremy

What is a suitable coupling for 500 revs/second?

Balance probably isn't a prime consideration, but no bending parts obviously.

I'd probably go for a rod though one shaft engaging a pair of driving dogs on the other, then spend half an hour adjusting it 'till it ran quiet

best

Robin
Good question. I've been looking at the small Huco and Lovejoy couplings and think I might be able to adapt one of the ones that uses an elastomer spider. Hopefully this will reduce any noise and allow for a small degree of misalignment. Now that I'm being less ambitious with my speed expectations (due to the difficulty in getting affordable bearings) the problem sould be simpler.

I may revert to driving the spindle with a small belt drive, as although this would be more bulky, it might well end up simpler to build.

Jeremy