[409vny]

Having difficulty setting up "steps per unit". Running Mach3 to Taig CNC mill with 20 tpi acme. So according to the Mach 3 instructions:

Default units set to mm
1.8 deg steppers
Xylotex XS-3525/8S-4 set for 1.8 deg

360 deg / 1.8 = 200 steps per turn
200 steps per turn times 20 tpi = 4000 steps per inch
Therefore 4000 / 25.4 = 157.48031 steps per mm

When I specify a 30mm circle at that setting it creates about a 6mm circle.
Then changed the steps per unit setting to 1574.48031 thinking maybe it calculated in cm internally and this resulted in about a 36mm circle. Kept taking a percentage off and now it is set at 1270 steps per unit which is close BUT there is no logic or reason to base this setting on other than trial and error so ...

..can I not read the Mach 3 instructions
..am I incapable of operating my calculator
..going senile
..all of the above

Any ideas or assistance greatly appreciated - thanks

[ger21]

Xylotex default is 8 microsteps, so you should have 20 x 200 x 8 = 32000 steps per inch, divided by 25.4 = 1259.8425

[409vny]

Plugged the numbers in and it's working perfectly. Thank you very much - you saved me from having to commit myself