UNCcoarse60° flank
1-1/8-7 UNC Thread Dimensions
1-1/8-7 UNC is a coarse pitch UNC thread. There are 7 threads per inch, giving a pitch of 3.63 mm. The recommended tap drill leaves roughly 75% thread engagement.
Nominal Ø28.57 mm
Pitch3.63 mm
Threads per inch7
Pitch Ø-31.29 mm
Tap drill-63.59 mm
Thread profile
millimetres unless stated- Designation
- 1-1/8-7 UNC
- Thread system
- UNC
- Series
- coarse
- Flank angle
- 60°
- Major diameter
- 28.57 mm / 1.12"
- Pitch
- 3.63 mm
- Threads per inch
- 7
- Pitch diameter
- -31.29 mm
- Minor diameter (external)
- -84.5 mm
- Minor diameter (internal)
- -71.2 mm
- Thread depth
- 56.54 mm
- Recommended tap drill
- Ø -63.59 mm / -2.5036"
How these values are derived
Basic ISO thread geometry uses the fundamental triangle height H = 0.866025 × P. External minor diameter d₃ = d − 1.226869 × P, internal minor diameter D₁ = d − 1.082532 × P. Tap drill is given as nominal diameter minus pitch, which approximates a 75% thread engagement — adjust for tough materials or deep holes.