BSPT Tapered Pipe Thread (R / Rp / Rc) · ISO 7-1 / EN 10226
R 1/4" Thread: Pitch, Tap Drill & Dimensions
R 1/4" is a BSPT Tapered Pipe Thread (R / Rp / Rc) (ISO 7-1 / EN 10226) size, with a major diameter of 13.157 mm, 19 threads per inch (1.337 mm pitch). The tap drill is 11.445 mm.
| Female Thread Diameter | Rp 1/4" |
|---|---|
| Pipe Minor Diameter (mm) | 8 |
| Pipe Major Diameter (mm) | 13.157 |
| Tapping Drill Size (mm) | 11.445 |
| TPI | 19 |
| Pitch (mm) | 1.337 |
| Flank angle | 55° |
| Taper | 1:16 |
Common questions
What size drill do I use to tap R 1/4"?
Use a 11.445 drill. This is the standard tap drill for R 1/4"; for hard materials or deep threads a slightly larger drill reduces tapping torque.
What is the pitch of R 1/4"?
The pitch of R 1/4" is 1.337, meaning the thread advances that distance in one full turn.
Where can I find other BSPT Tapered Pipe Thread (R / Rp / Rc) sizes?
The full BSPT Tapered Pipe Thread (R / Rp / Rc) 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.