--- type: "fit-designation" designation: "H7" letter: "H" it_grade: "ITIT7" feature: "hole" role: "The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it." 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/h7 --- # H7 Tolerance — ISO 286 Hole Limits by Nominal Size A 25 mm H7 hole runs 25.000 to 25.021 mm — deviations +0 to +21 µm on a 21 µm band. H7 is the ISO 286 hole tolerance built from fundamental deviation H and standard tolerance grade ITIT7. The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it. - **Designation**: H7 - **Feature**: hole - **Fundamental deviation**: H — Zero deviation — the basic hole - **Tolerance grade**: ITIT7 - **Typical use**: The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it. - **Standard**: ISO 286-1:2010, ISO 286-2:2010 ## H7 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 hole Ø (mm) | Max hole Ø (mm) | IT tolerance (µm) | | --- | --- | --- | --- | --- | --- | | [5 mm](https://shopmath.org/fits/h7/5mm.md) | +12 | +0 | 5.000 | 5.012 | 12 | | [6 mm](https://shopmath.org/fits/h7/6mm.md) | +12 | +0 | 6.000 | 6.012 | 12 | | [8 mm](https://shopmath.org/fits/h7/8mm.md) | +15 | +0 | 8.000 | 8.015 | 15 | | [10 mm](https://shopmath.org/fits/h7/10mm.md) | +15 | +0 | 10.000 | 10.015 | 15 | | [12 mm](https://shopmath.org/fits/h7/12mm.md) | +18 | +0 | 12.000 | 12.018 | 18 | | [16 mm](https://shopmath.org/fits/h7/16mm.md) | +18 | +0 | 16.000 | 16.018 | 18 | | [20 mm](https://shopmath.org/fits/h7/20mm.md) | +21 | +0 | 20.000 | 20.021 | 21 | | [25 mm](https://shopmath.org/fits/h7/25mm.md) | +21 | +0 | 25.000 | 25.021 | 21 | | [30 mm](https://shopmath.org/fits/h7/30mm.md) | +21 | +0 | 30.000 | 30.021 | 21 | | [40 mm](https://shopmath.org/fits/h7/40mm.md) | +25 | +0 | 40.000 | 40.025 | 25 | | [50 mm](https://shopmath.org/fits/h7/50mm.md) | +25 | +0 | 50.000 | 50.025 | 25 | | [80 mm](https://shopmath.org/fits/h7/80mm.md) | +30 | +0 | 80.000 | 80.030 | 30 | | [100 mm](https://shopmath.org/fits/h7/100mm.md) | +35 | +0 | 100.000 | 100.035 | 35 | _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 H7 ### H7 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 H7 Tolerance ### What is an H7 tolerance? H7 is an ISO 286 hole tolerance: fundamental deviation H at IT grade IT7. The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it. Zero deviation — the basic hole describes what the H deviation does. ### What is the tolerance on a 25 mm H7 hole? A 25 mm H7 hole runs 25.000 to 25.021 mm — deviations +0 to +21 µm, a tolerance band of 21 µm. ## Fits Built on H7 Standard hole/shaft pairs that use H7 as their hole. | 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. | | [H7/g6](https://shopmath.org/fits/h7-g6.md) | Clearance | hole basis | Sliding. Locates accurately, still moves and turns freely. | | [H7/p6](https://shopmath.org/fits/h7-p6.md) | Interference | hole basis | Locational interference. Rigid location in steel without the load capacity of a drive fit. | | [H7/r6](https://shopmath.org/fits/h7-r6.md) | Interference | hole basis | Medium drive. The joint itself carries load. | | [H7/k6](https://shopmath.org/fits/h7-k6.md) | Transition | hole basis | Locational transition. Accurate location, assembles with light force. | | [H7/m6](https://shopmath.org/fits/h7-m6.md) | Transition | hole basis | Locational transition, tighter than k6. | | [H7/n6](https://shopmath.org/fits/h7-n6.md) | Transition | hole basis | Tight transition. Usually a press job. | ## 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/h7) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*