I'm curious about these ultra high frequency spindles. You don't see much info on them here. I get that the ones made by Yager, GMN, Weiss and IMT are probably too expensive for your average hobby user but I noticed that cheaper copies from China and Taiwan have started appearing on eBay recently. ATC variants start as low as $1100. Is anyone here planning to buy one?
I had assumed that they were of little use outside of micro-engraving applications but Datron machines use them for full-on milling applications in aluminum and steel. I wonder if there would be any benefit in using one instead of your typical 24,000 rpm CNC router spindle on a machine for aluminum projects.
If anyone here has one, is it your main spindle or a 2nd spindle? What sort of project do you use them for? Why did you choose a 40,000 - 100,000 rpm spindle over a 24k one? Do you notice better results in terms of speed or part finish?