Technical
BSP, BSPT, NPT and metric fine threads with major diameter, tap drill and threads per inch.
Major diameter of the male thread and bore of the female thread – this is how to identify a thread with a calliper. All dimensions in mm.
| Size | Threads/inch | Pitch | Major Ø male thread | Minor Ø | Tap drill G (parallel) | Tap drill Rc (tapered) |
|---|---|---|---|---|---|---|
| 1/8" | 28 | 0,907 | 9,728 | 8,566 | 8,8 | 8,4 |
| 1/4" | 19 | 1,337 | 13,157 | 11,445 | 11,8 | 11,2 |
| 3/8" | 19 | 1,337 | 16,662 | 14,95 | 15,25 | 14,75 |
| 1/2" | 14 | 1,814 | 20,955 | 18,631 | 19,0 | 18,25 |
| 3/4" | 14 | 1,814 | 26,441 | 24,117 | 24,5 | 23,75 |
| 1" | 11 | 2,309 | 33,249 | 30,291 | 30,75 | 30,0 |
| 1 1/4" | 11 | 2,309 | 41,91 | 38,952 | 39,5 | 38,5 |
| 1 1/2" | 11 | 2,309 | 47,803 | 44,845 | 45,25 | 44,5 |
| 2" | 11 | 2,309 | 59,614 | 56,656 | 57,0 | 56,0 |
| Size | Threads/inch | Major Ø male thread | Tap drill (guide value) |
|---|---|---|---|
| 1/8" | 27 | 10,29 | 8,4 |
| 1/4" | 18 | 13,72 | 11,1 |
| 3/8" | 18 | 17,15 | 14,5 |
| 1/2" | 14 | 21,34 | 18,0 |
| 3/4" | 14 | 26,67 | 23,0 |
| 1" | 11,5 | 33,4 | 29,0 |
| 1 1/4" | 11,5 | 42,16 | 38,0 |
| 1 1/2" | 11,5 | 48,26 | 44,0 |
| 2" | 11,5 | 60,33 | 56,0 |
| Thread | Pitch | Major Ø male thread | Tap drill female thread |
|---|---|---|---|
| M8 × 1 | 1 | 8 | 7 |
| M10 × 1 | 1 | 10 | 9 |
| M12 × 1.5 | 1,5 | 12 | 10,5 |
| M14 × 1.5 | 1,5 | 14 | 12,5 |
| M16 × 1.5 | 1,5 | 16 | 14,5 |
| M18 × 1.5 | 1,5 | 18 | 16,5 |
| M20 × 1.5 | 1,5 | 20 | 18,5 |
| M22 × 1.5 | 1,5 | 22 | 20,5 |
| M24 × 1.5 | 1,5 | 24 | 22,5 |
| M26 × 1.5 | 1,5 | 26 | 24,5 |
| M27 × 2 | 2 | 27 | 25 |
| M30 × 2 | 2 | 30 | 28 |
| M33 × 2 | 2 | 33 | 31 |
| M36 × 2 | 2 | 36 | 34 |
| M42 × 2 | 2 | 42 | 40 |
| M45 × 2 | 2 | 45 | 43 |
| M48 × 2 | 2 | 48 | 46 |
| M52 × 2 | 2 | 52 | 50 |
BSP and BSPT have the same number of threads and nominal diameter, but cannot be combined freely. NPT and BSPT do not fit together despite their similar size (flank angle 60° instead of 55°).