ISO Metric Thread Calculator (Pitch, Minor and Stress Area)
Compute the basic geometry of an ISO metric thread from nominal diameter and pitch: pitch diameter d2, minor diameter d1, root diameter d3, tensile stress area As, thread depth and lead angle, per ISO 68-1 basic profile.
Advertisement
How to use this calculator
- Enter the nominal diameter D and pitch P in millimetres.
- Read pitch and minor diameters, the tensile stress area and the lead angle.
- Use the stress area for preload and bolt strength calculations.
Frequently asked questions
What are the formulas for d2 and d1?
For the ISO 60-degree metric basic profile: d2 = D - 0.649519 x P and d1 = D - 1.082532 x P, based on the basic triangle height H = 0.866 x P.
What is the tensile stress area As?
As is the effective area used for bolt strength and preload: As = pi/4 x ((d2 + d3)/2)^2 where d3 = D - 1.226869 x P. For M10 x 1.5 it is 58.0 mm2.
Does this include tolerance class 6H or 6g?
No, these are basic (zero tolerance) values. Tolerance classes shift the limits; use basic geometry for tooling and reference, and ISO 965 tables for gauging.