1. Take a strip of paper about 1" wide and long enough to completely circle the male thread.
2. Wrap this paper around the male thread snugly, making sure it is against the shoulder all the way around. At some point where the strip overlaps, pierce through both of the overlapped papers with a pin. (Fig. 1)
3. Then with the thumb, press the paper firmly against the threads around the entire circumference to leave an impression of the threads. (Use the end of a pencil if necessary to bring out the edge of the thread onto the paper.) (Fig. 2)
4. Remove the paper strip and circle each pin prick with a pencil.
5. The distance between these two points divided by 3.1416 equals the ODM (Outside diameter of the male).
6. The impressions on the paper give the number of threads per inch (TPI). Both the ODM and TPI are needed. (Fig. 3)
7. You may also use this same method to determine the outside diameter (OD) of a hose.

Note: Do not measure a badly worn thread. If only a worn thread is available, send the male fitting to Red Head for an accurate determination of the thread dimensions.