My sizes are out

[Doddy]

A couple of experiments for you to try.

*** CAUTION: Hand coded G-Code and un-tested. Sit next to your E-Stop!!! ***

test2.nc

This should slowly rock the X-axis by 0.5mm (or 18 degrees on a 1610 screw) - wrap a bit of tape around the x-axis screw with a visible tail and run this g-code through the controller and observe the tape. The G-code has got a feed rate of 10mm/min so my poor maths suggests around 3 seconds to go 0.5mm (18 degrees) and 3 seconds to go back to 0 (0 degrees). It repeats... a few times. No spindle and no z-movement.

This is just to verify that there's no backlash compensation active erroneously or not in the controller. You'll have to eyeball the 18 degrees rotation on the screw/tape.

Remove tape.

test.nc

This one cuts two pocket outlines - with your 12.7mm milling bit, starts at (0,0) and cuts a 3-tooth comb with a positive displacement on X, 50mm between teeth. After the 3rd tooth it reverses and cuts another 2 teeth offset in Y 30mm back the other way also 50mm apart. This to verify again that there's no backlash effects or compensation in operation.

Sorry, that's all I can think of at the moment.