2.5mm is a pretty big error. I use HSM, Tormach and mach3 often. I am using a good full version of mach3 and not the Tormach version but I SERIOUSLY doubt that has anything to do with it.

Send me your email and I will email you my post file since I don't know how to upload to here

One thing to try is to increase the allowable deviation from perfect in hsm. I don't have it open so I don't remember the exact terms, but HSM assumes you have a machine capable of High Speed Machining when the Tormach isn't even in the ballpark. My 2014 Haas gets bogged trying to run some of the code HSM outputs, but 15ipm seems like it should be able to handle it unless its a VERY tight radius. I use a large radius and ramp at .05" per step and run at 15ipm minute with 1/4 all the time and don't have any issues on my Tormach.

You can also send me the gcode and I can run it on my tormach and Haas in the morning and confirm if it is a control issue or not

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