H7/d8 fit — Loose running fit
ISO 286 hole-basis clearance fit. Enter a nominal size to get the limits.
About H7/d8
Free-running clearance for shafts in simple plain bearings subject to dirt, misalignment or thermal growth: material-handling rollers, low-speed gearbox shafts.
At Ø25 mm the hole H7 measures 0 mm to +0.021 mm and the shaft d8 −0.098 mm to −0.065 mm, giving a clearance of 0.065 mm to 0.119 mm.
How the limits are calculated
Hole H7: fundamental deviation EI = 0, standard tolerance IT7 = 21 µm for 18–30 mm. Shaft d8: fundamental deviation es = -65 µm, IT8 = 33 µm. Clearance = hole − shaft, evaluated at both extremes. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.
H7/d8 limits by size range
| Size (mm) | Hole H7 | Shaft d8 | Clearance min | Clearance max |
|---|---|---|---|---|
| ≤ 3 | +0.010 / 0 | −0.020 / −0.034 | +0.020 | +0.044 |
| 3 – 6 | +0.012 / 0 | −0.030 / −0.048 | +0.030 | +0.060 |
| 6 – 10 | +0.015 / 0 | −0.040 / −0.062 | +0.040 | +0.077 |
| 10 – 18 | +0.018 / 0 | −0.050 / −0.077 | +0.050 | +0.095 |
| 18 – 30 | +0.021 / 0 | −0.065 / −0.098 | +0.065 | +0.119 |
| 30 – 50 | +0.025 / 0 | −0.080 / −0.119 | +0.080 | +0.144 |
| 50 – 80 | +0.030 / 0 | −0.100 / −0.146 | +0.100 | +0.176 |
| 80 – 120 | +0.035 / 0 | −0.120 / −0.174 | +0.120 | +0.209 |
| 120 – 180 | +0.040 / 0 | −0.145 / −0.208 | +0.145 | +0.248 |
| 180 – 250 | +0.046 / 0 | −0.170 / −0.242 | +0.170 | +0.288 |
| 250 – 315 | +0.052 / 0 | −0.190 / −0.271 | +0.190 | +0.323 |
| 315 – 400 | +0.057 / 0 | −0.210 / −0.299 | +0.210 | +0.356 |
| 400 – 500 | +0.063 / 0 | −0.230 / −0.327 | +0.230 | +0.390 |
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 H7/d8 a clearance fit?
Yes — H7/d8 is a clearance fit per ISO 286 (see types of fits). At Ø25 mm it gives a clearance of 0.065 mm to 0.119 mm mm, depending which parts of the tolerance zones are paired.
What is the H7/d8 tolerance at 25 mm?
At a nominal size of Ø25 mm, H7 allows a hole diameter from 25.000 to 25.021 mm, and d8 allows a shaft diameter from 24.902 to 24.935 mm.