New to CNC.

[JAZZCNC]

I think I maybe having a unit metric vs imperial problem as I have done the sums regarding steps, revolutions and distance travelled but I am getting odd results.

What odd results.?

However, it's a simple enough calculation. Take the Micro steps set on the drives and divide by the pitch of the ball-screws taking into account any ratios if you have any. So let's say 1600 micro-steps and 5mm pitch, then 1600/5=320 Steps per MM.

This is what you enter into Mach3 steps per setting. This will give you the correct movement so if you are getting different results in the commanded distance then it's coming from elsewhere which could be from a number of places.

Secondly, it is a nema 34 8.7nm stepper on the axis (approx 1200mm 20mm dia 5mm pitch ) looking at the x axis motor movement profile what are suitable velocity and acceleration speeds? - (a nagging thought about being mechanically sympathetic)

Now that's not easy to answer because several factors come into play that determines how to set up the machine regards motor tuning and unfortunately it looks like you may have fallen foul of the "bigger is better" assumption when it comes to motors and this will now be robbing you of speed.

NEMA 34 motors of this size require lots of volts to get any decent speed from and I'd put a small wager on it you probably have less than 50V which will limit the RPM and torque, which when combined with a 5mm pitch will result in quite slow speeds.

Give more info on the electrical side ie: Drive make and Volts to drives, Micros steps set on drives.