Chinese Spindles

[Jonathan]

questions that arose in the thread including tool balancing, questions about hollowing the shaft and physical workable material in the shaft i thought it may be better to opt for a tormach like solution with atc which is where the man i2i has come up with the goods, the speed was just a side effect of the spindle rather than a requirement for the project,

Ahh fair enough, would have linked to that myself if I'd known! For me 6000rpm is useless as the tools I use the vast majority of the time run at 9000-13000rpm.
Making an ATC system for 6000rpm is a lot less challenging since, to an extent, balancing is no longer an issue. Also you can use much bigger/stronger angular contact bearings than at 24krpm which makes the design much easier. Still not saying it's a straightforward project, but I'd consider it as even though that spindle is a good price compared to the rest it's still a lot of money to spend...

For motors you've got lots of options at 6000rpm. Most standard induction motors will overspeed quite a lot, so a 2-pole motor and a belt will give plenty of power and options. However they're rather heavy and bulky.

The motor I used on my micro lathe is actually ideal here:

[That's odd - it's dissapeared from www.hobbyking.com, it was called 'Turnigy 80-100-B 130Kv' ... I'll email to find out where it's gone, hope it's not discontinued. They're available elsewhere but more expensive. http://endless-sphere.com/forums/vie...?f=28&t=39779]

Being rated for 6.5kW (as if!) means you could probably afford to run it direct drive and still have plenty of power at 1000rpm, athough it would still be better to have two ratios. Probably 3:1 and 1:1.