3/8-12 ACME Thread Dimensions

Basic information

Designation

3/8-12 ACME

Thread system

ACME

Series

acme

Standard

ASME B1.5

Basic profile

ACME basic profile

Flank angle

29°

Dimensions

Major diameter

0.3748 in / 9.52 mm

Pitch (metric equivalent)

2.117 mm

Threads per inch

12

Pitch diameter

0.3335 in / 8.47 mm

Minor diameter (external)

0.2717 in / 6.9 mm

Minor diameter (internal)

0.2717 in / 6.9 mm

Thread depth

0.0517 in / 1.312 mm

Recommended tap drill

Ø 0.2917 in / 7.41 mm

These 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.

No specification in this database uses 3/8-12 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.

Neighbouring sizes in ACME.