M18 × 1.5 fine Thread Dimensions
M18 x 1.5 (fine) is a fine ISO Metric thread. Pitch is 1.5 mm, equivalent to 16.93 threads per inch. The recommended tap drill is nominal diameter minus pitch.
Thread profile
millimetres unless statedBasic information
- Designation
- M18 x 1.5 (fine)
- Thread system
- ISO Metric
- Series
- fine
- Standard
- ISO 262
- Basic profile
- ISO 68-1 basic profile
- Flank angle
- 60°
Dimensions
- Major diameter
- 18 mm
- Pitch
- 1.5 mm
- Threads per inch
- 16.93
- Pitch diameter
- 17.03 mm
- Minor diameter (external)
- 16.16 mm
- Minor diameter (internal)
- 16.38 mm
- Thread depth
- 0.92 mm
- Recommended tap drill
- Ø 16.5 mm
How these values are derived
computed from the basic profileThese figures follow the ISO 68-1 basic profile of ISO 262. A 60° basic profile has a fundamental triangle height H = 0.866025 × P, with pitch diameter d₂ = d − 0.649519 × P, external minor diameter d₃ = d − 1.226869 × P and internal minor diameter D₁ = d − 1.082532 × P; the two minor diameters differ because the external root is rounded while the internal crest is truncated. 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 M18 × 1.5 fine yet.
Related
Other pitches at the same 18 mm diameter — a fine pitch on a coarse diameter, or the reverse, is the usual substitution question.
Neighbouring sizes in ISO Metric.