H8/m7 fit — Locational transition
ISO 286 hole-basis transition fit. Enter a nominal size to get the limits.
About H8/m7
Tighter than H8/n7, on an IT8 hole; a press-assembled locational fit for parts that must resist vibration but stay removable, where full H7/m6 precision isn't justified.
At Ø25 mm the hole H8 measures 0 mm to +0.033 mm and the shaft m7 +0.008 mm to +0.029 mm, giving between 0.029 mm interference and 0.025 mm clearance.
How the limits are calculated
Hole H8: fundamental deviation EI = 0, standard tolerance IT8 = 33 µm for 18–30 mm. Shaft m7: fundamental deviation ei = 8 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/m7 limits by size range
| Size (mm) | Hole H8 | Shaft m7 | Clearance min | Clearance max |
|---|---|---|---|---|
| ≤ 3 | +0.014 / 0 | +0.012 / +0.002 | −0.012 | +0.012 |
| 3 – 6 | +0.018 / 0 | +0.016 / +0.004 | −0.016 | +0.014 |
| 6 – 10 | +0.022 / 0 | +0.021 / +0.006 | −0.021 | +0.016 |
| 10 – 18 | +0.027 / 0 | +0.025 / +0.007 | −0.025 | +0.020 |
| 18 – 30 | +0.033 / 0 | +0.029 / +0.008 | −0.029 | +0.025 |
| 30 – 50 | +0.039 / 0 | +0.034 / +0.009 | −0.034 | +0.030 |
| 50 – 80 | +0.046 / 0 | +0.041 / +0.011 | −0.041 | +0.035 |
| 80 – 120 | +0.054 / 0 | +0.048 / +0.013 | −0.048 | +0.041 |
| 120 – 180 | +0.063 / 0 | +0.055 / +0.015 | −0.055 | +0.048 |
| 180 – 250 | +0.072 / 0 | +0.063 / +0.017 | −0.063 | +0.055 |
| 250 – 315 | +0.081 / 0 | +0.072 / +0.020 | −0.072 | +0.061 |
| 315 – 400 | +0.089 / 0 | +0.078 / +0.021 | −0.078 | +0.068 |
| 400 – 500 | +0.097 / 0 | +0.086 / +0.023 | −0.086 | +0.074 |
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/m7 a clearance fit?
Not always — H8/m7 is a transition fit per ISO 286 (see types of fits). At Ø25 mm it gives between 0.029 mm mm interference and 0.025 mm mm clearance, depending which parts of the tolerance zones are paired.
What is the H8/m7 tolerance at 25 mm?
At a nominal size of Ø25 mm, H8 allows a hole diameter from 25.000 to 25.033 mm, and m7 allows a shaft diameter from 25.008 to 25.029 mm.