ACMEacme29° flankASME B1.5

2-4 ACME Thread Dimensions

2-4 ACME is a acme ACME thread. There are 4 threads per inch on a 2 in major diameter, giving a metric-equivalent pitch of 6.35 mm. The recommended tap drill leaves roughly 75% thread engagement.

Major Ø2 in

Threads per inch4

Pitch (metric)6.35 mm

Pitch Ø1.8748 in

Tap drill1.75 in

Thread profile

millimetres unless stated

2-4 ACME — basic profile29° flank angle · Not to scale

Basic information

Designation: 2-4 ACME
Thread system: ACME
Series: acme
Standard: ASME B1.5
Basic profile: ACME basic profile
Flank angle: 29°

Dimensions

Major diameter: 2 in / 50.8 mm
Pitch (metric equivalent): 6.35 mm
Threads per inch: 4
Pitch diameter: 1.8748 in / 47.62 mm
Minor diameter (external): 1.7299 in / 43.94 mm
Minor diameter (internal): 1.7299 in / 43.94 mm
Thread depth: 0.135 in / 3.429 mm
Recommended tap drill: Ø 1.75 in / 44.45 mm

How these values are derived

computed from the basic profile

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.

Compatible parts0 specification pages

No specification in this database uses 2-4 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.

3/4-6 ACME 1-5 ACME 1-1/4-5 ACME 1-1/2-4 ACME