The pitch of a fastener refers to the distance between threads. This guide explains the different pitches available at different sizes of pipe plug.
Pipe threads are generally either BSP (British Standard Pipe) or NPT (National Pipe Thread). BSP threads can be parallel (BSPP - also known as 'G') or tapered (BSPT - also known as 'R').
Parallel essentially means the diameter of the threaded part of the fastener are the same width apart all the time. In contrast, a tapered thread reduces in diameter over the length of the threaded portion.
| Diameter | BSP (TPI) | NPT (TPI) |
|---|---|---|
| 1/8 | 28 | 27 |
| 1/4 | 19 | 18 |
| 3/8 | 19 | 18 |
| 1/2 | 14 | 14 |
| 3/4 | 14 | 14 |
| 1 | 11 | 11.5 |
| 1-1/4 | 11 | 11.5 |
| 1-1/2 | 11 | 11.5 |
| 2 | 11 | 11.5 |
| 2-1/2 | 11 | 8 |
| 3 | 11 | 8 |
| 3-1/2 | 11 | 8 |
| 4 | 11 | 8 |
| 5 | 11 | 8 |
| 6 | 11 | 8 |