I'm in the need for a high speed spindle (24k RPM) which can accommodate an ATC and use something like the Tormach ER20 holders.

Since these are readily available in the thousands of dollars for an import brand, I was wondering about making my own hollow spindle that can be used with an ATC setup and driving it with a side mounted 3hp water cooled Chinese spindle like the routers use. The spindle would have to be ground and balanced of course and some decent bearings but that seems doable for less than what it cost to buy one.

The only thing I see that may be an issue, is the side load on the spindle motor, but thinking about it, routers put a pretty good side load on the bearings already. at 24,000 RPM, the torque requirement for a belt is very low so a simple belt without too much tension should work pretty decent although I hadn't done the math yet.

The ATC itself and code is not problem as I have one I built and been using for sometime on my RF45, but now I want to add one to my CNC Router/Mill.
Yes, I mentioned mill for doing aluminum, 3D profiling at high speed.

Ideas and comments very welcome.

Richard