1-1/8-12 UNF Thread Dimensions
1-1/8-12 UNF is a fine Unified National Fine thread. There are 12 threads per inch on a 1.1248 in major diameter, giving a metric-equivalent pitch of 2.117 mm. The recommended tap drill leaves roughly 75% thread engagement.
Thread profile
millimetres unless statedBasic information
- Designation
- 1-1/8-12 UNF
- Thread system
- Unified National Fine
- Series
- fine
- Standard
- ASME B1.1
- Basic profile
- Unified basic profile
- Flank angle
- 60°
Dimensions
- Major diameter
- 1.1248 in / 28.57 mm
- Pitch (metric equivalent)
- 2.117 mm
- Threads per inch
- 12
- Pitch diameter
- 1.0709 in / 27.2 mm
- Minor diameter (external)
- 1.0228 in / 25.98 mm
- Minor diameter (internal)
- 1.0346 in / 26.28 mm
- Thread depth
- 0.0511 in / 1.298 mm
- Recommended tap drill
- Ø 1.0417 in / 26.46 mm
How these values are derived
computed from the basic profileThese figures follow the Unified basic profile of ASME B1.1. A 60° basic profile uses a fundamental triangle height H = 0.866025 × P, with external minor diameter d₃ = d − 1.226869 × P and internal minor diameter D₁ = d − 1.082532 × P; the two differ because the external root is rounded while the internal crest is truncated. A 55° Whitworth profile uses H = 0.960491 × P and a thread height of 0.640327 × P. The recommended tap drill is given as nominal diameter minus pitch, which approximates 75% thread engagement — adjust it for tough materials or deep holes.
Compatible parts0 specification pages
No specification in this database uses 1-1/8-12 UNF yet.
Related
Neighbouring sizes in Unified National Fine.