UNFfine60° flank

7/16-20 UNF Thread Dimensions

7/16-20 UNF is a fine pitch UNF thread. There are 20 threads per inch, giving a pitch of 1.27 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø11.11 mm
Pitch1.27 mm
Threads per inch20
Pitch Ø-9.84 mm
Tap drill-21.15 mm

Thread profile

millimetres unless stated
Thread profile — 7/16-20 UNFd 11.11d2 -9.84d3 -28.46mm60°P 1.27h3 19.79tap ⌀-21.15
7/16-20 UNF — basic profile60° flank angle · Not to scale
Designation
7/16-20 UNF
Thread system
UNF
Series
fine
Flank angle
60°
Major diameter
11.11 mm / 0.44"
Pitch
1.27 mm
Threads per inch
20
Pitch diameter
-9.84 mm
Minor diameter (external)
-28.46 mm
Minor diameter (internal)
-23.81 mm
Thread depth
19.79 mm
Recommended tap drill
Ø -21.15 mm / -0.8325"

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.