British Threads - British Standard Taper Pipe
BSTP (British Standard Taper Pipe) Thread Data
This thread is tapered, but with an 'interference' fit. Unlike BSP, it needs no seals or gaskets. Pressure tight joints are achieved by the thread alone..
BSPT (tapered) male will mate with a BSPT (tapered) female and the BSPP female swivel. The BSPT male has tapered threads and a 30-degree inverted seat. The thread pitch is different in most cases, and the thread angle is 55 degrees instead of the 60-degree angle found on NPTF threads. Neither the British parallel pipe or the British tapered pipe has true metric threads, although many people find these threads "foreign" and conclude they must be "metric."
Also referred to as British Standard Taper Pipe or Pipe Taper, or Conical Thread.
Taper is 3/4" taper per foot ( 1 in 16 on the diameter). Various other symbols are BSPT, BSPTr, PT, KR, Rc.
Angle of thread = 55°
| Nominal Size (inches) | T P I | Pitch (inches) | Major Diameter (inches) | Minor Diameter (inches) | Tapping Drill Size |
|---|---|---|---|---|---|
| 1/16 | 28 | 0.0357 | 0.304 | 0.2583 | 6.4 mm (0.2520 inch) |
| 1/8 | 28 | 0.0357 | 0.383 | 0.3372 | 8.4 mm (0.3307 inch) |
| 1/4 | 19 | 0.0526 | 0.518 | 0.4506 | 11.2 mm (0.4409 inch) |
| 3/8 | 19 | 0.0526 | 0.656 | 0.5886 | 14.75 mm (0.0507 inch) |
| 1/ 2 | 14 | 0.0714 | 0.825 | 0.7336 | 18.25 mm (0.7185 inch) |
| 3/4 | 14 | 0.0714 | 1.041 | 0.9496 | 23.75 mm (0.9350 inch) |
| 1 inch | 11 | 0.0909 | 1.309 | 1.1926 | 30 mm (1.1811 inch) |