[DavidhCNC]

I am trying to make a 1in 14TPI internal thread using the IPS. In using IPS for other processes I know its not perfect, but how does it calculate the K value?

If K = (major dia. - minor dia)/ 2, then according to my machinist handbook page 1284

K = (1 - .923) / 2 = .0385

But IPS gives me .056, where is it getting this value from?

[Billetgrip]

Are you sure IPS isn't giving you .046? Are you programming it like its an external thread?

I honestly don't see what it matters as long as it works out to your last pass being at 1.000 and your feed is correct.

[DavidhCNC]

I am using the internal threading program in the IPS. And I am sure its not .046. The TPI is correct, but the internal diameter always comes out too small, even on other threads. In fact, external threads come out too small as well, as in, the threads aren't deep enough. I end up running the threading program over and over again while adjusting the program to cut deeper or adjusting my offsets. I just can't make sense of it.

[Billetgrip]

Mine gives .0585 for K with the same info you've given.

Take your major diameter and subtract the X value before the G76 line. Divide that by 2. Then subtract your Dx.xxx. That is where the weird K is coming from.

If your X value in the G76 line is 1.000 and its not cutting to that then you X offset is incorrect or push off.