UNCcoarse60° flank

1/2-13 UNC Thread Dimensions

1/2-13 UNC is a coarse pitch UNC thread. There are 13 threads per inch, giving a pitch of 1.95 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø12.7 mm
Pitch1.95 mm
Threads per inch13
Pitch Ø-19.53 mm
Tap drill-36.93 mm

Thread profile

millimetres unless stated
Thread profile — 1/2-13 UNCd 12.7d2 -19.53d3 -48.19mm60°P 1.95h3 30.44tap ⌀-36.93
1/2-13 UNC — basic profile60° flank angle · Not to scale
Designation
1/2-13 UNC
Thread system
UNC
Series
coarse
Flank angle
60°
Major diameter
12.7 mm / 0.5"
Pitch
1.95 mm
Threads per inch
13
Pitch diameter
-19.53 mm
Minor diameter (external)
-48.19 mm
Minor diameter (internal)
-41.02 mm
Thread depth
30.44 mm
Recommended tap drill
Ø -36.93 mm / -1.4538"

How these values are derived

Basic ISO thread geometry uses the fundamental triangle height H = 0.866025 × P. External minor diameter d₃ = d − 1.226869 × P, internal minor diameter D₁ = d − 1.082532 × P. Tap drill is given as nominal diameter minus pitch, which approximates a 75% thread engagement — adjust for tough materials or deep holes.