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How to use it
Enter the nominal diameter and choose the tolerance position and grade for the hole and the shaft, or start from one of the typical fits. The result updates with every change: deviations in micrometres, limit diameters in millimetres, maximum and minimum clearance or interference and the type of fit.
- Clearance (H7/g6, H8/f7): parts that must slide or rotate, such as pins, guides and bushes.
- Transition (H7/k6, H7/n6): precise removable centring, such as bearings, pulleys and keyed wheels.
- Interference (H7/p6, H7/s6): shrink-fitted parts that transmit load by friction, assembled by press or thermal expansion.
How the calculation works
The ISO 286 system defines each tolerance with a letter, which sets the position of the zone relative to the zero line, and a number, the IT grade, which sets its width. Both depend on the size range the diameter falls into.
The tool uses the tables of IT grades 3 to 13 and of the fundamental deviations most used in general engineering (holes E–P, shafts d–p). For letters or grades outside this coverage, such as the r, s, u press fits, the values must be read directly from the standard.
What the calculation doesn't tell you
The right tolerance isn't chosen from the table but from the function: loads, operating temperatures, different hole and shaft materials, roughness and assembly method change the result. An interference fit also needs a check of contact pressure and transmissible torque. It's the kind of verification we carry out in contract mechanical design.
FAQ
What's the difference between hole-basis and shaft-basis?
In the hole-basis system the hole always has position H (zero lower deviation) and the shaft is varied; it's the most used because holes are made with fixed-size tools. In the shaft-basis system the shaft is kept at h and the hole is varied, useful for long drawn shafts carrying several components.
What's the right fit for a bearing?
It depends on which ring rotates relative to the load. For a rotating inner ring with normal load, k5, k6 or m6 are often used on the shaft; for a fixed housing H7 or J7. Precise recommendations are in the bearing manufacturer's catalogue.
Why does JS have symmetrical deviations?
The JS and js positions split the tolerance half above and half below the zero line: ±IT/2. They're used for locating dimensions where staying centred on the nominal value matters.
Do the values also apply above 500 mm?
No. Above 500 mm ISO 286 uses different formulas and tables; the tool is limited to the range up to 500 mm, which covers most general engineering.