Gerrit,
I want to build a small milling router for steel next year. I will use this motor (0.47 Nm) or the 0.6 Nm variant to drive the spindle at a 1:1 ratio. I will use the HSS tooling from my BF16 mill (max 6 mm diameter HSS, no carbide), that runs at max 3000 RPM. Doing so, I don't have to run that fast and can keep the construction "light weight" and the steppers small (Nema23 52 mm). I will make an ER11 spindle using 7000AC contact angle bearings. The motor will be besides the spindle and connected using a belt (thick O-ring). This makes the construction low and makes it easy to change the ratio. The O-ring also keeps the noise down.
Running at 8000 RPM when using small end mills is doable. Just beware of the max RPM of the bearings. Mine are rated for 3000 and high RPM bearings are pretty expensive.
Contact angle bearings and fan's consume a lot of power when running at high RPM. For cooling the motor I will make a heat sink. Mounting of the heat sink is easy because the motor has a round body. If passive cooling is not enough, I will add a small 24V fan.
Huub
