UNCcoarse60° flank
3/8-16 UNC Thread Dimensions
3/8-16 UNC is a coarse pitch UNC thread. There are 16 threads per inch, giving a pitch of 1.59 mm. The recommended tap drill leaves roughly 75% thread engagement.
Nominal Ø9.52 mm
Pitch1.59 mm
Threads per inch16
Pitch Ø-16.67 mm
Tap drill-30.8 mm
Thread profile
millimetres unless stated- Designation
- 3/8-16 UNC
- Thread system
- UNC
- Series
- coarse
- Flank angle
- 60°
- Major diameter
- 9.52 mm / 0.38"
- Pitch
- 1.59 mm
- Threads per inch
- 16
- Pitch diameter
- -16.67 mm
- Minor diameter (external)
- -39.95 mm
- Minor diameter (internal)
- -34.13 mm
- Thread depth
- 24.74 mm
- Recommended tap drill
- Ø -30.8 mm / -1.2125"
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.