Thanks everyone, that's really helpful.

m_c, yes I will be replacing the vee belts with timing belts to eliminate any slip. I want to be able the do fine threading in stainless so I was under the impression that I needed good control over the spindle.


Clive, I think I have settled on EMC so I can use the multi pulse spindle encoder like you suggested. so if the controller reacts to the spindle speed is it quick enough to pick up the change in spindle speed as cut starts? Im looking at as high a speed and max depth of cut as possible.

A_Camera, thanks for the link. That looks like a better option especially with the detachable panel. I will be using an inverter duty 4 pole motor to get the best performance over the speed range needed. they do one that can go from 150-3000rpm so should be perfect. As you say the advantage of the encoder feedback is that it goes down to 0 rpm so good for indexing.

Im still confused about the PID feedback as the inverter I mentioned shows an external connection to a speed pulse.

For the extra money of the closed loop VFDs I think I'll try the senorless first and upgrade later if and when needed.

Many thanks All