Quote Originally Posted by JOGARA View Post
Could well be backlash.
I just measured it again and my 22mm diameter is 0.04 under in the Y and 0.14 under in the X.
It is pretty close but next week I need to do a 190mm diameter hole and close fit a bearing in it.
Yes I am using a caliper... Need a bore gauge.

It is not as off as I thought but if I can get it close as possible, would be less nervous about the big part.
You can't measure a bore with calipers and believe that 0.04mm measurement or even the 0.14mm for that matter..!! . . . Only a bore gauge can do that with any accuracy.

Also, it's not just the gantry squareness you need to worry about, the spindle tram and parallelism of the rails all come into play and I know for sure that these machines are not good enough in either of those areas to machine a bore that size to any decent accuracy.