UNFfine60° flankASME B1.1

1-1/2-12 UNF Thread Dimensions

1-1/2-12 UNF is a fine Unified National Fine thread. There are 12 threads per inch on a 1.5 in major diameter, giving a metric-equivalent pitch of 2.117 mm. The recommended tap drill leaves roughly 75% thread engagement.

Major Ø1.5 in

Threads per inch12

Pitch (metric)2.117 mm

Pitch Ø1.4461 in

Tap drill1.4165 in

Thread profile

millimetres unless stated

1-1/2-12 UNF — basic profile60° flank angle · Not to scale

Basic information

Designation: 1-1/2-12 UNF
Thread system: Unified National Fine
Series: fine
Standard: ASME B1.1
Basic profile: Unified basic profile
Flank angle: 60°

Dimensions

Major diameter: 1.5 in / 38.1 mm
Pitch (metric equivalent): 2.117 mm
Threads per inch: 12
Pitch diameter: 1.4461 in / 36.73 mm
Minor diameter (external): 1.3976 in / 35.5 mm
Minor diameter (internal): 1.4098 in / 35.81 mm
Thread depth: 0.0511 in / 1.298 mm
Recommended tap drill: Ø 1.4165 in / 35.98 mm

How these values are derived

computed from the basic profile

These 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 1-1/2-12 UNF yet.

Neighbouring sizes in Unified National Fine.

7/8-14 UNF 1-12 UNF 1-1/8-12 UNF 1-1/4-12 UNF