Working on a project at work that is requiring me to design my own custom NPT (size restrictions on the part). I will need to design and manufacture both the internal and external plug for this part. With that said I'm having some issues programming it with Mastercam and checking my numbers that everything makes sense.

I need at least a .770 ID (so I'm calling my NPT ID .780) and will be using 14 TPI. For Mastercam it looks I need to select the Pitch Diameter when selecting my feature for the NPT? With standard thread I select my OD diameter so I'm not sure how to handle NPT.

The other thing is I determined my Pitch Diameter to be .826 with a major diameter of .908. Anyone care to confirm my math is adding up correctly?

Now where I'm getting stuck is I don't see how to determine my thread depth or thread length for that matter. Any input?

Once I have the internal thread done I haven't seen much on how to produce the physical taper on the plug I will be machining. I do have a lathe but its down for the count at the moment, Can I achieve this taper using some other method?