Thanks for the response. The XAxis is scaled and seems to work correctly. I attached a photo of the problem as well as the xml file for the machine. In the photo, the outer circle is correct and centered on the x. The inner circular pocket is skewed. The cut starts in the center at the x but moves +x on the part. The resolution in the photo isn't high enough to make out the circular machining marks but it definitely starts in the center. Again, the XAxis is set up properly. I've used Mach3 for a few years and am confident it works fine but in this case I'm not so sure. The toolpath preview in Mach3 looks normal however the actual toolpath on the part is not. I can't see where the stepper controls would do this. If I had another suitable PC my next step would be to install Mach3 on it and give it a try. I've reloaded Mach3 on the existing PC and that didn't correct the problem. By the way, the toolpath was generated with Aspire. I have checked this machine against known good toolpaths used in the past and the problem follows this machine. This is a new machine with Mach3 running on a spare WinXP Pro PC. Thanks again for any thoughts or ideas!