Ok, I have just checked the voltages from the spindle 3 board to the vfd and readings increase by roughly 1 volt per 1000 rpm (set the spindle to 1000 = 1v, 2000 = 2v ..... 9000 = 9v, 10000 = 10v). Everything over 10000 the spindle board just spits out 10v, and at 10v the vfd displays a speed of roughly 22000. This explains why I thought I had no control, I never tried to take the speed lower than 10000 so the it always ran at the same speed.

So I guess the issue would be with the config in mach 3 (motor tuning?)? I have just checked the mach 3 setup manual and I'm not sure it's in English! Even if I could get my head round it will i will still be stuck as I have no information on the vfd/spindle and therefore have no idea on the correct values to enter?

Am I stuck cutting everything at 22000?

Ic2 - thanks for the pulley tip, I was wondering why mach 3 kept moaning when I tried setting lower values! As for measuring the speed I do not have any tools to do that.... I only have the display of the vfd.

Jim