KEVOS® MAKEOS · Threads
ISO Metric Thread Limits of Size (6g, 6H and Others)
What are the limits of size for this metric thread in the chosen tolerance class?
Major, pitch and minor diameter limits of external and internal ISO metric threads for common tolerance classes (4h, 6h, 6g, 6f, 6e, 8g and 4H, 5H, 6H, 7H, 6G) from the ISO 965-1 tolerance formulas.
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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 | Thread pitch. |
| External class | choice | Tolerance class of the external thread (6g is the usual medium class). |
| Internal class | choice | Tolerance class of the internal thread (6H is the usual medium class). |
Method and formulas
- Fundamental deviations (µm): e = −(50 + 11P), f = −(30 + 11P), g = −(15 + 11P), h = 0; G = +(15 + 11P), H = 0.
- Grade 6 tolerances: Td = 180P^(2/3) − 3.15P^(−1/2); Td2 = 90P^0.4 d^0.1 (d = geometric mean of the ISO diameter range); TD2 = 1.32 Td2; TD1 = 433P − 190P^1.22 (P < 1) or 230P^0.7. Grades 4, 5, 7, 8 multiply by 0.63, 0.8, 1.25, 1.6.
- Tolerances are rounded to the R40 preferred-number series and deviations to whole micrometres, as ISO 965 does. Limits: d max = d + es, d2 max = d2 + es, minus the tolerances; internal D2 min = d2 + EI, D1 min = D1 + EI, plus the tolerances.
- Example: M10 × 1.5-6g has pitch diameter 8.994 / 8.862 mm; 6H has 9.026 / 9.196 mm.
Limitations
- ISO 965 tabulates values rounded to a preferred series; formula values can differ by a few micrometres. Use the ISO 965-2/-3 tables for acceptance.
- Root contour and minor diameter of external threads are not limited here.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Find inspection limits for special metric threads
- Set thread turning and milling sizes
- Compare tolerance classes
Who it is for
- Quality inspectors
- Machinists
- Design engineers
What you get
- External major and pitch diameter limits
- Internal minor and pitch diameter limits
- Fundamental deviations and tolerances
Interpreting the result
- Use these values to set up machining; inspect with gauges or the tabulated limits.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1867–1912. Topic reference; no source tables or recommended settings are reproduced.
- ISO 965-1 ISO general purpose metric screw threads — Tolerances
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Open the ISO Metric Thread Limits of Size (6g, 6H and Others) calculator
