To be honest with you here Ross...I would rather go and buy one of those Chinese spindles on ebay,just seen one for £130 or nearest offer.
Yes but I want a ER 32 collet and 8000rpm is still to fast for milling. its also part of a whole one piece Z axis that I'm trying to design.

Your taking this to the extreme by worrying about precision from the motor and its housed bearings arrangement,too much headache.
Well its my hobby and I like to do things properly. I what to learn how to machine accurately so If nothing else it will be a learning exercise.


I wonder if you need to break this down a bit. Maybe convert a big old mill to cnc for the lower speed, big roughing out work in Ali, and concentrate on making a high speed VFD controlled spindle (20,000 - 30,000 rpm) for the gentle stuff and the routing in wood.
Yeah I'm coming to that conclusion. Although not with two machines (I'm not made of money...) but with a cartridge type spindle that can be swapped for different jobs, A/C for high speed and taper bearings for high load.


From what I've found the problem seems to Lay with heat.....

For high load you need a high contact angle 40 deg or more and therefore more friction, and heat but for high speed you need the opposite, a low contact angle (15 to 25deg. seems to be the favorite) which reduces the heat but also the load capacity. so therefore it would seem you cant have both (Unless any one knows different?)

The heat also affects the preload which in turn affects rigidity. for high speed you need a variable spring loaded one but the most rigid is the fixed permanent type

Hence "Mills for milling and routers for routing", but at least I now know why :heehee:

Anyway this should really simplify the design and manufacture of the separate spindles