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.
![Smiley :)](https://www.machsupport.com/forum/Smileys/default/smiley.gif)
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.