Hi,

This is an educated guess - I suspect it's a bug in Mach.

I say this because I've learned that Mach is not consistent about handling coordinate transformations when reporting G31 touch points. For example Mach does not handle Coordinate rotations and G31 correctly (where that means "mathematically correctly").

Since the formula you are using should be treated (from a math viewpoint) as a concatenated coordinate transformation, I have this gut level feeling that this could be another example of not all parts of mach uniformly handling all other parts of mach....

My suggestion would be to get a (as simple as possible) reproducible test case, write up the steps to show the problem and then contact Andrew at artsoft

Andrew is the first line bug checker these days - if you can show the problem to him, he can be the path to further action inside artsoft.

Dave