UNC Unified Coarse Thread · ANSI/ASME B1.1
1 1/4" - 7 UNC Thread: Pitch, Tap Drill & Dimensions
1 1/4" - 7 UNC is a UNC Unified Coarse Thread (ANSI/ASME B1.1) size, with a major diameter of 31.750 mm, 7 threads per inch (3.628 mm pitch). The tap drill is 28.05 mm.
| Major Diameter (inch) | 1.250 |
|---|---|
| Major Diameter (mm) | 31.750 |
| Tapping Drill Size (mm) | 28.05 |
| TPI | 7 |
| Pitch (mm) | 3.628 |
| Flank angle | 60° |
Common questions
What size drill do I use to tap 1 1/4" - 7 UNC?
Use a 28.05 drill. This is the standard tap drill for 1 1/4" - 7 UNC; for hard materials or deep threads a slightly larger drill reduces tapping torque.
What is the pitch of 1 1/4" - 7 UNC?
The pitch of 1 1/4" - 7 UNC is 3.628, meaning the thread advances that distance in one full turn.
Where can I find other UNC Unified Coarse Thread sizes?
The full UNC Unified Coarse Thread 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.