H8/u7 fit — Force fit
ISO 286 hole-basis interference fit. Enter a nominal size to get the limits.
About H8/u7
Coarser heavy press or shrink fit for permanent assemblies. See press fit tolerance for interference by size across the p6–u6 family.
At Ø25 mm the hole H8 measures 0 mm to +0.033 mm and the shaft u7 +0.048 mm to +0.069 mm, giving an interference of 0.015 mm to 0.069 mm.
How the limits are calculated
Hole H8: fundamental deviation EI = 0, standard tolerance IT8 = 33 µm for 18–30 mm. Shaft u7: fundamental deviation ei = 48 µm, IT7 = 21 µm. Clearance = hole − shaft, evaluated at both extremes. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.
H8/u7 limits by size range
| Size (mm) | Hole H8 | Shaft u7 | Clearance min | Clearance max |
|---|---|---|---|---|
| ≤ 3 | +0.014 / 0 | +0.028 / +0.018 | −0.028 | −0.004 |
| 3 – 6 | +0.018 / 0 | +0.035 / +0.023 | −0.035 | −0.005 |
| 6 – 10 | +0.022 / 0 | +0.043 / +0.028 | −0.043 | −0.006 |
| 10 – 18 | +0.027 / 0 | +0.051 / +0.033 | −0.051 | −0.006 |
| 18 – 30 | +0.033 / 0 | +0.069 / +0.048 | −0.069 | −0.015 |
| 30 – 50 | +0.039 / 0 | +0.095 / +0.070 | −0.095 | −0.031 |
| 50 – 80 | +0.046 / 0 | +0.132 / +0.102 | −0.132 | −0.056 |
| 80 – 120 | +0.054 / 0 | +0.179 / +0.144 | −0.179 | −0.090 |
| 120 – 180 | +0.063 / 0 | +0.250 / +0.210 | −0.250 | −0.147 |
| 180 – 250 | +0.072 / 0 | +0.330 / +0.284 | −0.330 | −0.212 |
| 250 – 315 | +0.081 / 0 | +0.402 / +0.350 | −0.402 | −0.269 |
| 315 – 400 | +0.089 / 0 | +0.492 / +0.435 | −0.492 | −0.346 |
| 400 – 500 | +0.097 / 0 | +0.603 / +0.540 | −0.603 | −0.443 |
Deviations in mm at the upper end of each range; negative clearance = interference. Clearance columns are shown on wider screens. Sub-ranges (e.g. 18–24 / 24–30) can differ for r, s, t, u, v, x, y, z — use the calculator for the exact size. “—” means ISO 286 doesn't define this class below that size (e.g. t only starts at 24 mm).
Is H8/u7 a clearance fit?
No — H8/u7 is an interference fit per ISO 286 (see types of fits). At Ø25 mm it gives an interference of 0.015 mm to 0.069 mm mm, depending which parts of the tolerance zones are paired.
What is the H8/u7 tolerance at 25 mm?
At a nominal size of Ø25 mm, H8 allows a hole diameter from 25.000 to 25.033 mm, and u7 allows a shaft diameter from 25.048 to 25.069 mm.