BSPP Parallel Pipe Thread (G) · ISO 228-1 / DIN 259
G 1 1/4" Thread: Pitch, Tap Drill & Dimensions
G 1 1/4" is a BSPP Parallel Pipe Thread (G) (ISO 228-1 / DIN 259) size, with a major diameter of 41.910 mm, 11 threads per inch (2.309 mm pitch). The tap drill is 38.953 mm.
| Major Diameter (inch) | 1.650 |
|---|---|
| Major Diameter (mm) | 41.910 |
| Minor Diameter Nut (mm) | 39.592 |
| Tapping Drill Size (mm) | 38.953 |
| TPI | 11 |
| Pitch (mm) | 2.309 |
| Flank angle | 55° |
Common questions
What size drill do I use to tap G 1 1/4"?
Use a 38.953 drill. This is the standard tap drill for G 1 1/4"; for hard materials or deep threads a slightly larger drill reduces tapping torque.
What is the pitch of G 1 1/4"?
The pitch of G 1 1/4" is 2.309, meaning the thread advances that distance in one full turn.
Where can I find other BSPP Parallel Pipe Thread (G) sizes?
The full BSPP Parallel Pipe Thread (G) table, with every size and a live filter, is on its standard page, and the Thread Finder searches all 73 standards at once.
Reference values; computed values use the ISO basic profile. Verify against the current standard before production use.