UNCcoarse60° flankASME B1.1

#1-64 UNC Thread Dimensions

#1-64 UNC is a coarse Unified National Coarse thread. There are 64 threads per inch on a 0.0728 in major diameter, giving a metric-equivalent pitch of 0.397 mm. The recommended tap drill leaves roughly 75% thread engagement.

Major Ø0.0728 in
Threads per inch64
Pitch (metric)0.397 mm
Pitch Ø0.063 in
Tap drill0.0575 in

Thread profile

millimetres unless stated
Thread profile — #1-64 UNCd 1.85d2 1.6d3 1.37mm60°P 0.397h3 0.243tap ⌀1.46
#1-64 UNC — basic profile60° flank angle · Not to scale

Basic information

Designation
#1-64 UNC
Thread system
Unified National Coarse
Series
coarse
Standard
ASME B1.1
Basic profile
Unified basic profile
Flank angle
60°

Dimensions

Major diameter
0.0728 in / 1.85 mm
Pitch (metric equivalent)
0.397 mm
Threads per inch
64
Pitch diameter
0.063 in / 1.6 mm
Minor diameter (external)
0.0539 in / 1.37 mm
Minor diameter (internal)
0.0559 in / 1.42 mm
Thread depth
0.0096 in / 0.243 mm
Recommended tap drill
Ø 0.0575 in / 1.46 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 #1-64 UNC yet.

Related

Neighbouring sizes in Unified National Coarse.

#2-56 UNC#3-48 UNC#4-40 UNC#5-40 UNC