Type in .375, Hit Enter. Clich the Pitch button. Now for some math. Rhino does not know how to give you threads per inch. You will have to tell her.
Lets have a look.
We now want to set up a guide line. In the Right view, Zoom in to the right bottom section of the helix as shown. Note how it runs through the helix on the right side. In the right view, Zoom in so you have a nice close look at the bottom left of the helix. American Standard Threads are cut at a 60 deg angle.