--- type: "fit-designation" designation: "h6" letter: "h" it_grade: "ITIT6" feature: "shaft" role: "Precision basic shaft — zero upper deviation, the reference for locational clearance fits." size_count: 13 size_range_mm: "5–100" standard: "ISO 286-1:2010, ISO 286-2:2010" verified: "August 1, 2026" url: https://shopmath.org/fits/h6 --- # h6 Tolerance — ISO 286 Shaft Limits by Nominal Size A 25 mm h6 shaft runs 24.987 to 25.000 mm — deviations -13 to +0 µm on a 13 µm band. h6 is the ISO 286 shaft tolerance built from fundamental deviation h and standard tolerance grade ITIT6. Precision basic shaft — zero upper deviation, the reference for locational clearance fits. - **Designation**: h6 - **Feature**: shaft - **Fundamental deviation**: h — Zero deviation — the basic shaft - **Tolerance grade**: ITIT6 - **Typical use**: Precision basic shaft — zero upper deviation, the reference for locational clearance fits. - **Standard**: ISO 286-1:2010, ISO 286-2:2010 ## h6 Limits and Deviations by Nominal Size Deviations are in micrometres from the nominal size; limits are the finished diameters in millimetres. Sizes that carry their own page are linked. | Nominal size | Upper deviation (µm) | Lower deviation (µm) | Min shaft Ø (mm) | Max shaft Ø (mm) | IT tolerance (µm) | | --- | --- | --- | --- | --- | --- | | [5 mm](https://shopmath.org/fits/h6/5mm.md) | +0 | -8 | 4.992 | 5.000 | 8 | | [6 mm](https://shopmath.org/fits/h6/6mm.md) | +0 | -8 | 5.992 | 6.000 | 8 | | [8 mm](https://shopmath.org/fits/h6/8mm.md) | +0 | -9 | 7.991 | 8.000 | 9 | | [10 mm](https://shopmath.org/fits/h6/10mm.md) | +0 | -9 | 9.991 | 10.000 | 9 | | [12 mm](https://shopmath.org/fits/h6/12mm.md) | +0 | -11 | 11.989 | 12.000 | 11 | | [16 mm](https://shopmath.org/fits/h6/16mm.md) | +0 | -11 | 15.989 | 16.000 | 11 | | [20 mm](https://shopmath.org/fits/h6/20mm.md) | +0 | -13 | 19.987 | 20.000 | 13 | | [25 mm](https://shopmath.org/fits/h6/25mm.md) | +0 | -13 | 24.987 | 25.000 | 13 | | [30 mm](https://shopmath.org/fits/h6/30mm.md) | +0 | -13 | 29.987 | 30.000 | 13 | | [40 mm](https://shopmath.org/fits/h6/40mm.md) | +0 | -16 | 39.984 | 40.000 | 16 | | [50 mm](https://shopmath.org/fits/h6/50mm.md) | +0 | -16 | 49.984 | 50.000 | 16 | | [80 mm](https://shopmath.org/fits/h6/80mm.md) | +0 | -19 | 79.981 | 80.000 | 19 | | [100 mm](https://shopmath.org/fits/h6/100mm.md) | +0 | -22 | 99.978 | 100.000 | 22 | _ISO 286 tabulates deviations per size band, so a value holds across the whole band a nominal size falls in, not just at that exact diameter._ ## Sources and Method for h6 ### h6 deviations - **Source**: limits computed from the compiled ISO 286 tables: ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell - **Method**: computed - **Verified against**: parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed ### Assumptions - Values are the ISO 286-2 tabulated limits, not the ISO 286-1 formula: the formula deviates from the table by up to 13.26% and is carried only as a validation harness. - Limits are at 20 °C, the ISO 1 reference temperature. - Dataset scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula. **Data last verified**: August 1, 2026 ## Common Questions About the h6 Tolerance ### What is an h6 tolerance? h6 is an ISO 286 shaft tolerance: fundamental deviation h at IT grade IT6. Precision basic shaft — zero upper deviation, the reference for locational clearance fits. Zero deviation — the basic shaft describes what the h deviation does. ### What is the tolerance on a 25 mm h6 shaft? A 25 mm h6 shaft runs 24.987 to 25.000 mm — deviations -13 to +0 µm, a tolerance band of 13 µm. ## Fits Built on h6 Standard hole/shaft pairs that use h6 as their shaft. | Fit | Classification | Basis | Typical use | | --- | --- | --- | --- | | [H7/h6](https://shopmath.org/fits/h7-h6.md) | Clearance | both basis | Locational clearance. Assembles by hand, no free movement intended. | | [G7/h6](https://shopmath.org/fits/g7-h6.md) | Clearance | shaft basis | Sliding, shaft basis. The h6 shaft is the reference and the hole carries the clearance. | | [P7/h6](https://shopmath.org/fits/p7-h6.md) | Interference | shaft basis | Locational interference, shaft basis. | | [K7/h6](https://shopmath.org/fits/k7-h6.md) | Transition | shaft basis | Locational transition, shaft basis. | | [N7/h6](https://shopmath.org/fits/n7-h6.md) | Transition | shaft basis | Tight transition, shaft basis. | ## Related pages - All fits and tolerances: [ISO 286 fit reference](https://shopmath.org/fits.md) - Full grade table: [ISO 286 tolerance chart](https://shopmath.org/charts/iso-tolerances.md) --- *Source: [ShopMath](https://shopmath.org/fits/h6) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*