My mill has metric lead screws, but everything I do is in US units (inches).   Any worry with me setting native units to inches, then entering a converted decimal amount under motor tuning "steps per".  Or should I be setting it to metric and just use US units G-code?

thanks

Just set your native units to inches. When you calculate the axis steps per unit it comes out at a long decimal number but Mach handles that without issue.  

Tweakie.

Great  - thanks