1-1/4-5 ACME Thread Dimensions
1-1/4-5 ACME is a acme ACME thread. There are 5 threads per inch on a 1.25 in major diameter, giving a metric-equivalent pitch of 5.08 mm. The recommended tap drill leaves roughly 75% thread engagement.
Thread profile
millimetres unless statedBasic information
- Designation
- 1-1/4-5 ACME
- Thread system
- ACME
- Series
- acme
- Standard
- ASME B1.5
- Basic profile
- ACME basic profile
- Flank angle
- 29°
Dimensions
- Major diameter
- 1.25 in / 31.75 mm
- Pitch (metric equivalent)
- 5.08 mm
- Threads per inch
- 5
- Pitch diameter
- 1.15 in / 29.21 mm
- Minor diameter (external)
- 1.0299 in / 26.16 mm
- Minor diameter (internal)
- 1.0299 in / 26.16 mm
- Thread depth
- 0.11 in / 2.794 mm
- Recommended tap drill
- Ø 1.05 in / 26.67 mm
How these values are derived
computed from the basic profileThese figures follow the ACME basic profile of ASME B1.5. 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 1-1/4-5 ACME. Power threads are not fastener threads — they are found on lead screws, jacks and vice screws, so no bolt or nut in this catalogue is made in this form. The geometry above is what a machinist needs to cut it.
Related
Neighbouring sizes in ACME.