Ok, I have been fooling around most of the day with this. If I try to calibrate the stepper motors using the milling program. I get very high speeds which change each time I turn on mach3. If I switch from the milling side to turn, then the motors go on a dead slow. The information from one side of the program is not transferred to the other, which is a bit silly.  So can anyone help. I have tried to follow the manual, but the last instruction on the calculation is just nonsense. So here is the information I have. My leadscrew is 18 TPI . The motor encoder is set to 4000 steps per revolution. The motor is set to 200 turns per revolution. The motor is connected to a pulley with 19teeth, this connects to the leadscrew pulley with 22 teeth.  Can someone please help me out here. Why can,t calibration of a lathe be simple like the milling machine.

What do you means by milling side and turn? Is this Mach3 or Mach3?  In M3 you in effect have 2 programs with different machine profiles with no connection between them? I can't imagine M4 is different. 

Hi, so I found out. I just don’t understand why mach3 turn makes it so hard to calibrate the motors.

Ho-hum.  Well I'm not quite sure what your information means, but I assume that you have a stepper-servo drive with a 4000 line encoder, the stepper being 200 steps/rev.  If I understand these devices correctly, the stepper is irrelevant, it just needs 4000 input pulses to get one rev of the motor.  The goal is to set a parameter in M3 which is steps/unit, i.e. steps/inch.  No real need to calibrate if your machine data is correct (though 18 tpi is an odd leadscrew pitch!).  (Getting 4000 steps out of a 200 step/rev motor just needs "microstepping" by a factor of 20 which is handled by the driver.)

You need 18 turns of the LS to get 1 inch of movement.  This corresponds to 22/19 revs of the motor (why those ratios? Seem rather odd).  So steps per inch is 18 x (22/19) x 4000 = 83,368.421052631578947368421052632 STEPS though you could ignore everything after the first decimal place.

Could you actually have a metric leadscrew of 0.7mm pitch?  Even then that's odd as feedscrews are usually chosen so one rev is a convenient feed in native units.

I run my lathe in metric, it has a 5mm pitch cross-feed screw but an 8 tpi leadscrew.  Steps/mm for both were calculated as above and are exact as far as I can measure

Hi, the leadscrew is odd. However it’s On a  German manufactured lathe so anything goes. I am in the U.K. so it’s all metric here these days. I must thank you for your help. But I do wish that who ever wrote the turn program had put in the auto calibration has in the mill program it would of taken all the pain out of sorting the lathe out. I will try your numbers and see how it works out. Thanks again.

"it’s On a  German manufactured lathe so anything goes"?  Most likely to be metric then.  Good luck.  You don't need auto-cal, you can do the same by just setting in a number for steps per, asking the lathe to move one unit and measuring how far it actually moves, then scaling the number you first thought of.

It’s an odd lathe for sure. However I just wish that artsoft had just input the auto calibration on the lathe software. I have looked at mach4 and they have also left it out. So it’s back and forth with the motors all day, when it was just a two minute job. It’s a pity. But he’ll what else is there to do.

Do the calculations! Or just type the number I gave you in steps per unit box.