maching Aluminium with sub 4mm bits

[Chaz]

You can certainly find spindles like this but they are pricey. For precision, you can also look at air bearing spindles but lots of money. What size bits are you cutting with that need this RPM? I run a 24000 rpm spindle on my main concrete mill and this works for alu without an issue.

Sub 4mm in the title, OK, but still, unless you are doing sub 1mm, just run at 24K RPM and adjust the feeds accordingly. Is saving 50% of the machining time (lets assume your machine can run high speed accurately) worth a couple of K on a new spindle?

[kell]

yes will be going down to at least 0.50mm