UNCcoarse60° flank

#3-48 UNC Thread Dimensions

#3-48 UNC is a coarse pitch UNC thread. There are 48 threads per inch, giving a pitch of 0.53 mm. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø2.51 mm
Pitch0.53 mm
Threads per inch48
Pitch Ø-6.22 mm
Tap drill-10.93 mm

Thread profile

millimetres unless stated
Thread profile — #3-48 UNCd 2.51d2 -6.22d3 -13.98mm60°P 0.53h3 8.25tap ⌀-10.93
#3-48 UNC — basic profile60° flank angle · Not to scale
Designation
#3-48 UNC
Thread system
UNC
Series
coarse
Flank angle
60°
Major diameter
2.51 mm / 0.1"
Pitch
0.53 mm
Threads per inch
48
Pitch diameter
-6.22 mm
Minor diameter (external)
-13.98 mm
Minor diameter (internal)
-12.04 mm
Thread depth
8.25 mm
Recommended tap drill
Ø -10.93 mm / -0.4302"

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.