I've started this new thread here, rather than continue on the collet discussion thread.

Prompted by the discussion on collet types in the other thread, I purchased an ER16 collet chuck, with a straight 20mm shank 100mm long, from Arc Euro, together with a couple of collets. My intention is to build a relatively high speed spindle for my CNC router project.

First off, full marks to Arc Euro - less than 24 hours from order to delivery.

I've just ordered a suitable motor, but have reduced my maximum speed requirement a bit to make bearing choice more affordable. The motor and speed controller I've opted for is rated at 550 watts, but my power will be limited to about 360 watts by the 12V, 30A power supply I already have.

The motor is a three phase brushless one, with a Kv of 1400, giving me a maximum rpm of about 16,800 at 12V. Total cost for the motor and speed controller, including postage, was just under £33.

I've also just ordered some deep groove bearings, that are rated at 20,000rpm, so should be OK in this application (I hope).

I'm hoping to be able to build a fairly high speed spindle, suitable for light duty routing with small diameter tools and a high degree of accuracy. The ER16 chuck is pretty good as far as I can tell. I can't see a difference on a DTI between the run out on the shaft OD (due to the innacuracy of my 3 jaw lathe chuck that I stuck it in to test) and the run out of a 1/4" bit of tool steel in the collet. My guess is that it's better than about 1/2 thou TIR, which should be OK for fine work like PCB milling.

Next job is turning up a bit of 2 1/2" diameter alloy bar to make the housing, then milling a mounting flat on it to allow it to fit to the Z axis plate. The motor will be directly coupled to the top of the spindle. I'm hoping that the combination of direct drive and a three phase brushless motor should make for a quiet spindle.

I'll post pictures as soon as I get something machined up.

Jeremy