BSPP Parallel Pipe Thread (G) · ISO 228-1 / DIN 259
G 1/4" Thread: Pitch, Tap Drill & Dimensions
G 1/4" is a BSPP Parallel Pipe Thread (G) (ISO 228-1 / DIN 259) size, with a major diameter of 13.157 mm, 19 threads per inch (1.337 mm pitch). The tap drill is 11.445 mm.
| Major Diameter (inch) | 0.518 |
|---|---|
| Major Diameter (mm) | 13.157 |
| Minor Diameter Nut (mm) | 11.890 |
| Tapping Drill Size (mm) | 11.445 |
| TPI | 19 |
| Pitch (mm) | 1.337 |
| Flank angle | 55° |
Common questions
What size drill do I use to tap G 1/4"?
Use a 11.445 drill. This is the standard tap drill for G 1/4"; for hard materials or deep threads a slightly larger drill reduces tapping torque.
What is the pitch of G 1/4"?
The pitch of G 1/4" is 1.337, 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.