UNFfine60° flank

#2-64 UNF Thread Dimensions

#2-64 UNF is a fine pitch UNF thread. There are 64 threads per inch, giving a pitch of 0.4 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø2.18 mm
Pitch0.4 mm
Threads per inch64
Pitch Ø-4.36 mm
Tap drill-7.9 mm

Thread profile

millimetres unless stated
Thread profile — #2-64 UNFd 2.18d2 -4.36d3 -10.18mm60°P 0.4h3 6.18tap ⌀-7.9
#2-64 UNF — basic profile60° flank angle · Not to scale
Designation
#2-64 UNF
Thread system
UNF
Series
fine
Flank angle
60°
Major diameter
2.18 mm / 0.09"
Pitch
0.4 mm
Threads per inch
64
Pitch diameter
-4.36 mm
Minor diameter (external)
-10.18 mm
Minor diameter (internal)
-8.73 mm
Thread depth
6.18 mm
Recommended tap drill
Ø -7.9 mm / -0.3109"

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.