UNFfine60° flank

3/4-16 UNF Thread Dimensions

3/4-16 UNF is a fine pitch UNF thread. There are 16 threads per inch, giving a pitch of 1.59 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø19.05 mm
Pitch1.59 mm
Threads per inch16
Pitch Ø-7.14 mm
Tap drill-21.27 mm

Thread profile

millimetres unless stated
Thread profile — 3/4-16 UNFd 19.05d2 -7.14d3 -30.42mm60°P 1.59h3 24.74tap ⌀-21.27
3/4-16 UNF — basic profile60° flank angle · Not to scale
Designation
3/4-16 UNF
Thread system
UNF
Series
fine
Flank angle
60°
Major diameter
19.05 mm / 0.75"
Pitch
1.59 mm
Threads per inch
16
Pitch diameter
-7.14 mm
Minor diameter (external)
-30.42 mm
Minor diameter (internal)
-24.6 mm
Thread depth
24.74 mm
Recommended tap drill
Ø -21.27 mm / -0.8375"

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.