3 Axis CNC router

[JAZZCNC]

You know how you have geared (if not 1-1) your motor to the ballscrew. You know what microstep setting you have used. This gives an exact "steps per" value, and if the machine isn't achieving this, you really need to find out why.

Actually neal it's not that simple and I pretty much guarantee you that if your using timing belts then the steps per won't work out per the calcs.
This is one reason why mach's calibration is best used for most people who are using belts and only have basic measuring tools.
Even then it still won't be spot on and can be improved upon. But to do this you need Linear scales and to measure over large distance.

When I build a machine I initially set it up using the calcs then I fine tune using linear scales and EVERY TIME the steps per is different to the calcs. Close but it's always bit lower or bit higher.