UNCcoarse60° flank
#8-32 UNC Thread Dimensions
#8-32 UNC is a coarse pitch UNC thread. There are 32 threads per inch, giving a pitch of 0.79 mm. The recommended tap drill leaves roughly 75% thread engagement.
Nominal Ø4.17 mm
Pitch0.79 mm
Threads per inch32
Pitch Ø-8.93 mm
Tap drill-15.99 mm
Thread profile
millimetres unless stated- Designation
- #8-32 UNC
- Thread system
- UNC
- Series
- coarse
- Flank angle
- 60°
- Major diameter
- 4.17 mm / 0.16"
- Pitch
- 0.79 mm
- Threads per inch
- 32
- Pitch diameter
- -8.93 mm
- Minor diameter (external)
- -20.57 mm
- Minor diameter (internal)
- -17.66 mm
- Thread depth
- 12.37 mm
- Recommended tap drill
- Ø -15.99 mm / -0.6297"
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.