M39 × 4 Thread Dimensions
M39 x 4 is a coarse ISO Metric thread. Pitch is 4 mm, equivalent to 6.35 threads per inch. The recommended tap drill leaves roughly 75% thread engagement.
Thread profile
millimetres unless statedBasic information
- Designation
- M39 x 4
- Thread system
- ISO Metric
- Series
- coarse
- Standard
- ISO 261
- Basic profile
- ISO 68-1 basic profile
- Flank angle
- 60°
Dimensions
- Major diameter
- 39 mm
- Pitch
- 4 mm
- Threads per inch
- 6.35
- Pitch diameter
- 36.4 mm
- Minor diameter (external)
- 34.09 mm
- Minor diameter (internal)
- 34.67 mm
- Thread depth
- 2.454 mm
- Recommended tap drill
- Ø 35 mm
How these values are derived
computed from the basic profileThese figures follow the ISO 68-1 basic profile of ISO 261. A 60° basic profile uses a fundamental triangle height H = 0.866025 × P, with external minor diameter d₃ = d − 1.226869 × P and internal minor diameter D₁ = d − 1.082532 × P; the two differ because the external root is rounded while the internal crest is truncated. A 55° Whitworth profile uses H = 0.960491 × P and a thread height of 0.640327 × P. The recommended tap drill is given as nominal diameter minus pitch, which approximates 75% thread engagement — adjust it for tough materials or deep holes.
Compatible parts0 specification pages
No specification in this database uses M39 × 4 yet.
Related
Other pitches at the same 39 mm diameter — a fine pitch on a coarse diameter, or the reverse, is the usual substitution question.
Neighbouring sizes in ISO Metric.