Re: Spindle rpm 8000-24000?
If you want to spend the $$$$ you can get spindles that will run 0-24,000 RPM, but you are not going to find them on Amazon. I have one that will do it, 12KW I think. (not for sale) Several thousand $ new.
In order to get a useful range that you want, you need to get into the heavy industrial stuff.
As Gerry said, if you try to do this with the small spindles you will instantly fry them.
If you really need the lower speed ranges, then separate the motor and spindle and use a belt drive so you can change speed ranges.
Jim Dawson
Sandy, Oregon, USA