So I purchased one of those Chinese knock offs, it actually runs fairly well but I need some help... In Mach 3 they have you set it to mm, then motor tuning set steps to 400 , velocity to 2000 and accel to 200. This is for x and y. It works well enough, but I need inches! This is where I need help if I change Mach config to inches the cnc doesn't like it at all. Is the motor tuning in mm and need to be converted? Need help going from a mm setup to inches...

This is the cnc:
CNC 3020 Router ENGRAVER Drilling Milling Machine H | eBay

Heres the manual on my skydrive
http://sdrv.ms/10hAFR1


Any help is appreciated

First thing is Config menu then Native Units and set to Inch.
Next go to motor tuning and multiply Steps per unit by 25.4 and divide Velocity and Acceleration by 25.4 then press Save Axis
Do the same for the rest of the axes, remembering to press Save Axis before you move to next one.
Once that is done restart Mach and you should be all set.
Hood

Looks like thats working, going to test the accuracy. When I put in the velocity as 78.74 and save it mach changes it to 78.72, any idea why its doing that? Will that affect the accuracy of a cut or is it really the steps that are accountable for that?

Its the Steps per unit setting that determines the accuracy. Velocity and Accel could affect accuracy if they are set too high such that a stepper stalls but other than that have no effect.
Hood

I also have a "3020 cnc" from China sold by MIB and I also want to switch it to inches. But my instructions say 320 steps. I wasn't sure what to divide or multiply by 25.4 but thanks hood I will try this tomorrow morning.