Basic Thread Dimensions
*Â The below values are nomoinal (without tolerances) and are valid for both external and internal threads.
| Thread Family |
BSPP (G) |
| Relevant Standards |
ISO 228-1, ISO 228-2 |
Tolerances for all Classes
BSPP G 1/4 (Internal Thread)
| Property |
Minimum |
Maximum |
| Minor Diameter (D1) |
11.445 mm (0.4506 ") |
11.89 mm (0.4681 ") |
| Pitch Diameter (D2) |
12.301 mm (0.4843 ") |
12.426 mm (0.4892 ") |
BSPP G 1/4-A (External Higher precision)
| Property |
Minimum |
Maximum |
| Major Diameter (d) |
12.907 mm (0.5081 ") |
13.157 mm (0.518 ") |
| Pitch Diameter (d2) |
12.176 mm (0.4794 ") |
12.301 mm (0.4843 ") |
BSPP G 1/4-A (External Low precision
| Property |
Minimum |
Maximum |
| Major Diameter (d) |
12.907 mm (0.5081 ") |
13.157 mm (0.518 ") |
| Pitch Diameter (d2) |
12.051 mm (0.4744 ") |
12.301 mm (0.4843 ") |
* For More Threadibg Information go to the BSP Thread Calculator
