How To Measure Thread Size Plumbing. Subtract 1/4 inch (0.25) from the od measurement. Measure the outside diameter of the large portion of the thread at a;
In addition to checking npt and bspt pipe sizes, use the two included gauges for measuring thread pitch. The pitch is the distance from a point on the peak of a thread to the same point on the next thread. Measure the thread's outer diameter (od) in inches.
How to measure your thread:
Inch thread sizes are specified by diameter and threads per inch. Find figure nea rest this dimension in column 1 or 2 of chart. Spread the ruler across the diameter of the pipe and measure. The pitch is the distance from a point on the peak of a thread to the same point on the next thread.