Pipe thread metric can be directly measured by vernier caliper and pitch gauge; for pipe threads English and American, also have the corresponding screw pitch gauge to measure, but how to measure the diameter of thread? How about a vernier caliper? Some threads are tapered. Which point is the measurement accurate? Never figured it out. As the imperial R1/2-14 and American NPT 1/2-14 this thread how to distinguish?
Inch thread is an isosceles triangle with 55 degrees, 60 degrees is made of an equilateral triangle, if you have a good tooth type gauge measurement, also the same number of teeth have more teeth than American english. Therefore, the two threads in your subject are short in length and inch in english.
What's the amount of taper thread you want? This is really a bad amount. Taper pipe threads are specified: within the range of the effective thread length, there is any place that meets the requirements (as you say, NPT1/2), because the pipe threads are sealed with little depth. Only a few teeth used for sealing, but the thread specification according to the requirements, for example, you say NPT1/2-14, then the pitch is 1/14 inches, in addition, the effective thread in a certain position must be the nominal diameter of 1/2 inch. I don't know, I said so, you know, no, no, I don't have a good idea for you, but I'm sure I didn't cheat you. I'm doing this, not an expert, but it's my business, huh?.
A dental gauge is something like a saw tooth, except that it is a standard thread type. In addition, English is 55 degrees 60 degrees is made of an isosceles triangle, isosceles triangle, you draw a sketch will find their bottom is along the axial thread, therefore, the same height of the triangle (i.e. the same nominal diameter) bottom 55 degrees less than 60 degrees, so the cumulative 55 degrees, the number of triangles in the on the line of the same length (number of teeth) than 60 DEG triangular.
