Hi again Sage.
At the risk of sounding a bit defensive you need to read and comprehend ... the text you
edited out of my post said that I
then took 0.5mm OFF as a FINISHING cut which would make it 40.0mm !!
The purpose of the exercise was to see what differences there were between TCNC3 and Mach3. Each test consisted of three actions - manually driving the tool by MDI, then doing the same but from a gcode file and finaly one was to see if radiusing the corners had any bearing on the outcome as the part I was working on when I found this issue has radiused corners. Pretty simple really and I'm sorry if it confusses you.
TCNC3 had the parts to within 0.02mm (0.0005") whereas Mach3 was up to 0.11mm (0.004") out - by my calculations that's 8 times 'worse'. You need to remember that I usually work in metric and 0.01mm is roughly 0.00025". To people who usually work in imperial 0.02 looks like allot - but it's not!!
And again as
already stated Graham has the code and is doing his own testing.
If I get the chance later today I will make some test files and post them here.