Power output in High Frequency spindles

You have to add a much bigger motor or some other type of drive to generate the torque you need.

If speed goes down a factor of 60 then torque has to go up the same factor to hold power at a constant level!

So a motor this big will overload the bearings as radial and axial forces go up with torque.

Best choice would be a big PMDC motor coupled to the shaft by a very good belt drive. Flat belt recommended almost totally encircling the wheel at the spindle by two elastically suspended rollers.

RHABE

I concur fully. The bearings will not tolerate such abuse. If you force it, you will end up with no functioning spindle at all. Much better buying one with the right specification.