H8/h9 fit — Locational clearance
ISO 286 hole-basis clearance fit. Enter a nominal size to get the limits.
About H8/h9
Wide, low-cost sliding/locating fit on an IT8 hole for parts that just need to go together and stay roughly aligned: guards, covers, non-critical linkage pins.
At Ø25 mm the hole H8 measures 0 mm to +0.033 mm and the shaft h9 −0.052 mm to 0 mm, giving a clearance of 0.000 mm to 0.085 mm.
How the limits are calculated
Hole H8: fundamental deviation EI = 0, standard tolerance IT8 = 33 µm for 18–30 mm. Shaft h9: fundamental deviation es = 0, IT9 = 52 µm. Clearance = hole − shaft, evaluated at both extremes. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.
H8/h9 limits by size range
| Size (mm) | Hole H8 | Shaft h9 | Clearance min | Clearance max |
|---|---|---|---|---|
| ≤ 3 | +0.014 / 0 | 0 / −0.025 | 0 | +0.039 |
| 3 – 6 | +0.018 / 0 | 0 / −0.030 | 0 | +0.048 |
| 6 – 10 | +0.022 / 0 | 0 / −0.036 | 0 | +0.058 |
| 10 – 18 | +0.027 / 0 | 0 / −0.043 | 0 | +0.070 |
| 18 – 30 | +0.033 / 0 | 0 / −0.052 | 0 | +0.085 |
| 30 – 50 | +0.039 / 0 | 0 / −0.062 | 0 | +0.101 |
| 50 – 80 | +0.046 / 0 | 0 / −0.074 | 0 | +0.120 |
| 80 – 120 | +0.054 / 0 | 0 / −0.087 | 0 | +0.141 |
| 120 – 180 | +0.063 / 0 | 0 / −0.100 | 0 | +0.163 |
| 180 – 250 | +0.072 / 0 | 0 / −0.115 | 0 | +0.187 |
| 250 – 315 | +0.081 / 0 | 0 / −0.130 | 0 | +0.211 |
| 315 – 400 | +0.089 / 0 | 0 / −0.140 | 0 | +0.229 |
| 400 – 500 | +0.097 / 0 | 0 / −0.155 | 0 | +0.252 |
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/h9 a clearance fit?
Yes — H8/h9 is a clearance fit per ISO 286 (see types of fits). At Ø25 mm it gives a clearance of 0.000 mm to 0.085 mm mm, depending which parts of the tolerance zones are paired.
What is the H8/h9 tolerance at 25 mm?
At a nominal size of Ø25 mm, H8 allows a hole diameter from 25.000 to 25.033 mm, and h9 allows a shaft diameter from 24.948 to 25.000 mm.