tonyfoale
6,000 RPM is fine,I have done lots of them, some up to 12,000 RPM, the whole Head has to be modified to do these speeds, the noise from using a timing belt is very high,at those speeds, it's best to use a poly-V Belt, Everything has to be balanced, including the Drive motor, good quality Bearing fitted to the Drive motor, unless you are able to do rigid tapping then the Poly-v Belt is the best