UNFfine60° flank

#4-48 UNF Thread Dimensions

#4-48 UNF is a fine pitch UNF thread. There are 48 threads per inch, giving a pitch of 0.53 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø2.84 mm
Pitch0.53 mm
Threads per inch48
Pitch Ø-5.89 mm
Tap drill-10.6 mm

Thread profile

millimetres unless stated
Thread profile — #4-48 UNFd 2.84d2 -5.89d3 -13.65mm60°P 0.53h3 8.25tap ⌀-10.6
#4-48 UNF — basic profile60° flank angle · Not to scale
Designation
#4-48 UNF
Thread system
UNF
Series
fine
Flank angle
60°
Major diameter
2.84 mm / 0.11"
Pitch
0.53 mm
Threads per inch
48
Pitch diameter
-5.89 mm
Minor diameter (external)
-13.65 mm
Minor diameter (internal)
-11.71 mm
Thread depth
8.25 mm
Recommended tap drill
Ø -10.6 mm / -0.4172"

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.