UNFfine60° flank

#8-36 UNF Thread Dimensions

#8-36 UNF is a fine pitch UNF thread. There are 36 threads per inch, giving a pitch of 0.71 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø4.17 mm
Pitch0.71 mm
Threads per inch36
Pitch Ø-7.47 mm
Tap drill-13.76 mm

Thread profile

millimetres unless stated
Thread profile — #8-36 UNFd 4.17d2 -7.47d3 -17.82mm60°P 0.71h3 10.99tap ⌀-13.76
#8-36 UNF — basic profile60° flank angle · Not to scale
Designation
#8-36 UNF
Thread system
UNF
Series
fine
Flank angle
60°
Major diameter
4.17 mm / 0.16"
Pitch
0.71 mm
Threads per inch
36
Pitch diameter
-7.47 mm
Minor diameter (external)
-17.82 mm
Minor diameter (internal)
-15.23 mm
Thread depth
10.99 mm
Recommended tap drill
Ø -13.76 mm / -0.5416"

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.