What does BSP thread mean?
There are two types of BSP (British Standard Pipe) threads:
BSPP which is ‘BSP Parallel Thread’
BSPT which is ‘BSP Taper Thread’
BSP is common in Australia and the commonwealth countries. It is based on trade size rather than actual diameter which can lead to some confusion when measuring ports.
BSP threads do not follow the same dimension as there description indicates, for example 1” BSPP thread does not measure 1” (25.4mm) diameter:
What is BSP thread size?
| BSPP Size | Male Thread Outside Diameter | Female Thread Inside Diameter | Threads Per Inch (TPI) |
| 1/8” | 9.6mm/0.38” | 8.6mm/0.34” | 28 |
| ¼” | 13mm/0.51” | 11.9mm/0.47” | 19 |
| 3/8” | 16.5mm/0.65” | 15.2mm/0.60” | 19 |
| ½” | 20.8mm/0.82” | 19.1mm/0.75” | 14 |
| 5/8” | 22.8mm/0.90” | 20.8mm/0.82” | 14 |
| ¾” | 26.3mm/1.04” | 24.6mm/0.97” | 14 |
| 1” | 33.1mm/1.30” | 30.7mm/1.21” | 11 |
| 1¼” | 41.8mm/1.64” | 39.4mm/1.55” | 11 |
| 1½” | 47.7mm/1.88” | 45.5mm/1.79” | 11 |
| 2” | 59.5mm/2.34” | 57.4mm/2.26” | 11 |
Whats the difference between BSP and NPT threads?
BSP threads have a 55o angle and rounded peaks and valleys, where as an NPT thread has a 60o angle and flattened peaks and valleys, most sizes also have a different amount of threads per inch (TPI).
Are BSP threads tapered?
BSP threads can be either Parallel (BSPP) or Taper (BSPT).
How do i measure BSP threads?
BSP threads are measured on the outside diameter and threads per inch (TPI)
Can i use BSP with NPT?
Due to the different threads per inch (TPI) and thread angles, BSP and NPT are not compatible.
BSP thread sizes
BSP thread sizes are available in 1/8”, ¼”, 3/8”, 5/8”, ¾”, 1”, 1¼”, 1½”, 2” and less common larger sizes of 2½”, 3”, 4”, 5” and 6”
