Well, prototyping of the Arcsin board has led me to build another high-speed spindle so I can CNC drill the next proto. I was also looking for a super quiet solution. Here is what I came up with.
I tried many different AC motors from the thrift store and finally settled on the open frame brushed AC motor from an old salad-shooter. This thing must turn at least 15k rpm, and is very quiet.
I turned the spindle and housing to suit my needs and then milled a flat on the housing so I could bolt it to a flat plate. I also borrowed the O-ring drive system that I used on the original green PCB mill. This setup works very well and only took a few hours of late-night machine work to complete.
The trickiest part is getting the spindle bore exactly in the center of the shaft so the tiny bits show zero runout. I somehow managed to get a perfectly centered hole on the first try. That is a .0145" drill bit spinning somewhere in the 20k rpm range on skate bearings with no wobble!
After a quick install onto the TK421, I drilled a few holes and tested the new spindle out. It works great and will definitely be used to drill the holes on the next Arcsin proto.
Ahhhhh! No ear piercing noise. This thing is very quiet and generates very limited vibration. Cool how the brush arcing turned out.