NPSM is a lesser-known pipe thread standard series defined in ASTM B1.20. This thread series creates a non-pressure tight connection. It is mainly used in mechanical joints and special applications with no internal pressure and, consequently, no sealing requirements. It is possible to achieve a seal with the aid of an O-ring.
The profile íorm is similar to that of UN threads.
The allowance and tolerances are identical to UN threads in Class 2A for external threads and class 2B for internal threads.
Truncation is calculated according to the below formulas:
