KEVOS® MAKEOS · Threads
ISO Metric Thread Basic Dimensions
What are the basic pitch, minor and root diameters and stress area of this metric thread?
Basic dimensions of an ISO metric (M) thread from nominal diameter and pitch: pitch and minor diameters, thread height, tensile stress area, lead angle and proof load.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Nominal diameter | mm | Nominal (basic major) diameter. |
| Pitch | mm | Pitch from the thread designation (coarse M12 is 1.75 mm). |
| Number of starts | starts | Number of starts; 1 for normal fastener threads. |
| Proof strength (0 = not needed) | MPa | Proof stress for the bolt property class (ISO 898-1), to give a proof load; 0 to skip. |
Method and formulas
- H = 0.866025P; d₂ = d − 0.649519P; D₁ = d − 1.082532P; d₃ = d − 1.226869P.
- Tensile stress area As = π/4 ((d₂ + d₃)/2)² = π/4 (d − 0.938194P)².
- Lead = starts × P; lead angle = atan(lead ÷ π d₂).
- Example: M12 × 1.75 has d₂ = 10.863 mm, D₁ = 10.106 mm and As = 84.267 mm².
Limitations
- Basic profile only; tolerance class limits (e.g. 6g/6H) come from ISO 965 tables.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check thread dimensions for design or inspection
- Find the stress area for bolt calculations
- Set CNC thread-milling and turning depths
Who it is for
- Design engineers
- CNC programmers
- Quality inspectors
What you get
- Basic pitch diameter
- Basic minor diameters (internal and external root)
- Fundamental triangle and thread heights
- Tensile stress area and proof load
- Lead and lead angle
Interpreting the result
- Use the stress area for bolt stress and the minor diameter for shear through the thread.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1867–1890. Topic reference; no source tables or recommended settings are reproduced.
- ISO 68-1 (basic profile) and ISO 724 (basic dimensions) — https://www.iso.org/standard/4166.html
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