I'm trying to do some taper threading with my ST20Y. I think I've got it mostly figured out except for the "I" value. I'm trying to make 1 1/4" 11.5 NPT threads for a guy doing some rural water well services. This is the code I have so far. I put question marks by the "I" value. How do I figure "I" for different threads in the future? Thanks
BTW there's a facing operation before this that has all the G20 yada yada.
I think I have my X value wrong as well. That's the diameter at the end closest to the chuck. I think it needs to be the diameter at the beginning of the thread?
The I-value is the incremental change in diameter as the tool cuts the thread pass. It's not just the thread angle, instead you have to trig it out based on the distance from the starting Z to the target Z.
For your reference, NPT threads have an angle of 1 degree 47 minutes. (1.7833 degrees).