DIY CNC machine for steel?

[Sven]

You can also opt for building in epoxy concrete (often called epoxy granite).
And yes, you can use a chinese spindle but the bearings have to be ok.

A guy close to me built an epoxy concrete machine with a chinese spindle (I think 2200 watts but up to 18000 rpm) and can easily mill steel, to about 200s of a mm.
He used old servos but you can get simmilar results with closed loop steppers.

Have a look over here in a dutch thread (maybe use google translate):
http://cnczone.nl/viewtopic.php?f=8&t=8410&hilit=epoxy&start=406

Here it is
Here it is in action, steel 12000rpm, 4500mm/min feed, 15mm doc, 0.5mm, at long life settings:


He says he can also do 20000rpm en 9500mm/min but that is no good for tool life.