Hi Paul,

I have tried to jog the machine and I can manually jog the machine with the bit and z set to top of material to beyond th 15.6mm depth by another 27mm You might be onto something though, as it is the shortest bit I own and have tried to cut all the way through my material.

The gcode has the lines to suggest it is cutting to 15.6mm and 13.8mm, which I guess is the tabs and the final cut depth?

I just tried setting the z a little bellow the top surface to see if it would cut deeper and I did along some of the part and then went back to being above bottom of the panel surface. I wonder if there may be some slippage with the collet, so I may look at this now. It's a 3.175mm mm bit in a 3mm collet, but maybe as the bit is shorter it is only holding at the end of the collet? I don't have this issue when using my 3mm engraving bit, but then I'm only milling a few mm into the top surface. The next collet down is a 1.5-2mm collet, so it may not fit.

Thanks for your help guys, unfortunately the plot thickens.