I did a test job on the weekend and found that the holes were .2mm undersized, could this be backlash?? whats the best way to measure for backlash??

Thanks

Jim

Backlash will show up in circles as either flat spots at the cardinal points or even an oval shape depending on how bad the backlash is.

Easy way to test for backlash is place a Dial indicator on the table, mag base on table and point agains the head or quill and then jog one way  for a wee bit. Zero the axis DRO then put Mach into step jog mode and set the step increment to maybe 0.01mm and start to jog the opposite way a step at a time. As soon as you see the needle move your backlash has been taken up and you can see how much by reading the DRO.
Hood

Tools bend. It could be just tool deflection.

or an undersize endmill

Improper tool dia. description in whatever CAM you might be using ? ? ?

Thanks for all the info, I've also noticed that it's taped too, so I guess this must be tool bend, it was a 6mm end mill cutting alloy, at 4mm stages, I guess I should add a finish cut with .5mm wall?