UNFfine60° flank
3/8-24 UNF Thread Dimensions
3/8-24 UNF is a fine pitch UNF thread. There are 24 threads per inch, giving a pitch of 1.06 mm. The recommended tap drill leaves roughly 75% thread engagement.
Nominal Ø9.52 mm
Pitch1.06 mm
Threads per inch24
Pitch Ø-7.94 mm
Tap drill-17.36 mm
Thread profile
millimetres unless stated- Designation
- 3/8-24 UNF
- Thread system
- UNF
- Series
- fine
- Flank angle
- 60°
- Major diameter
- 9.52 mm / 0.38"
- Pitch
- 1.06 mm
- Threads per inch
- 24
- Pitch diameter
- -7.94 mm
- Minor diameter (external)
- -23.46 mm
- Minor diameter (internal)
- -19.58 mm
- Thread depth
- 16.49 mm
- Recommended tap drill
- Ø -17.36 mm / -0.6833"
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.