I needed some help programming a 1/8-27 NPT external thread on the lathe. Controller on lathe is Mitsubishi.

The thread is .3125 long. I have to go about .035" past .3125" to account for the .035" shoulder on the threading insert. I will start threading .2" in front of the part.

**Also, one of the things I am confused about is which thread height to use in calculations. Do you use the "height of the sharp V thread" or "maximum height of thread" for your P value and to calculate your X? Refer to the link. For right now in the code below, I will use the "maximum height of thread".**

NPT Thread Calculator

Here is what I have. Let me know if it is right or wrong.

Major Diameter of Big End: .405

Maximum height of thread = .0296

X value = .405 - (2 * .0296) = .3457

Z value = .3125 + .035 = .348

P = 296 since maximum height of thread is .0296

F = 1/27 = .03704

We know that an NPT thread is 1.7899 degrees. So to calculate R....

R = (.3125+.035+.2)tan(1.7899) = .0171

Therefore, my G76 line looks like this:

**G76 X.3457 Z-.348 R-.0171 P296 F.03704**

Again, I am not sure if you have to use "height of sharp v thread" or "maximum thread height" for your X calculations and P value. If anybody here knows, please chime in. Also, please tell me if my G76 line is correct or not.

For depth of each cut, # of spring passes, etc that is already in the controller settings. That info is not needed in the G code since it is already in the mits controller settings.

Angelw, you probably know this.

Thanks,

Chris