GRBL resolution

Hi,

I am trying to mill circuit boards at the moment with varying success.

One thing I have noticed while just setting up is 0.1mm in the GRBL interface does not equal 1mm (10x0.1 doesnt move the same distance as 1mm). This is a massive pain for setting up the Z especially when I am milling to a depth of 0.1mm.

I am wondering if this is what I should expect or there is something up with the mill.

I notice a little bit of play in the collet too, it moves up and down slightly even with everything tight. It is a bit stiff, so I am wondering if this is designed to avoid breaking bits... or is this perhaps why I am seeing issues with the 0.1mm.

Thank you,
Paul