H8 tolerance (hole, IT8)
Hole tolerance class H8 per ISO 286-1:2010: fundamental deviation EI = 0, grade IT8 (14 µm at ≤ 3 mm to 97 µm at 400–500 mm). For an exact size, open the calculator with H8 selected.
- Type
- Hole
- Grade
- IT8
- Tolerance
- 14 … 97 µm
- Fund. deviation
- EI = 0
H8 limits by size range
| Size (mm) | Upper (µm) | Lower (µm) | Ø max (mm) | Ø min (mm) | Upper (mm) | Lower (mm) | Dev. (in) |
|---|---|---|---|---|---|---|---|
| ≤ 3 | +14 | 0 | 3.014 | 3.000 | +0.014 | 0 | +0.00055 / 0 |
| 3 – 6 | +18 | 0 | 6.018 | 6.000 | +0.018 | 0 | +0.00071 / 0 |
| 6 – 10 | +22 | 0 | 10.022 | 10.000 | +0.022 | 0 | +0.00087 / 0 |
| 10 – 14 | +27 | 0 | 14.027 | 14.000 | +0.027 | 0 | +0.00106 / 0 |
| 14 – 18 | +27 | 0 | 18.027 | 18.000 | +0.027 | 0 | +0.00106 / 0 |
| 18 – 24 | +33 | 0 | 24.033 | 24.000 | +0.033 | 0 | +0.00130 / 0 |
| 24 – 30 | +33 | 0 | 30.033 | 30.000 | +0.033 | 0 | +0.00130 / 0 |
| 30 – 40 | +39 | 0 | 40.039 | 40.000 | +0.039 | 0 | +0.00154 / 0 |
| 40 – 50 | +39 | 0 | 50.039 | 50.000 | +0.039 | 0 | +0.00154 / 0 |
| 50 – 65 | +46 | 0 | 65.046 | 65.000 | +0.046 | 0 | +0.00181 / 0 |
| 65 – 80 | +46 | 0 | 80.046 | 80.000 | +0.046 | 0 | +0.00181 / 0 |
| 80 – 100 | +54 | 0 | 100.054 | 100.000 | +0.054 | 0 | +0.00213 / 0 |
| 100 – 120 | +54 | 0 | 120.054 | 120.000 | +0.054 | 0 | +0.00213 / 0 |
| 120 – 140 | +63 | 0 | 140.063 | 140.000 | +0.063 | 0 | +0.00248 / 0 |
| 140 – 160 | +63 | 0 | 160.063 | 160.000 | +0.063 | 0 | +0.00248 / 0 |
| 160 – 180 | +63 | 0 | 180.063 | 180.000 | +0.063 | 0 | +0.00248 / 0 |
| 180 – 200 | +72 | 0 | 200.072 | 200.000 | +0.072 | 0 | +0.00283 / 0 |
| 200 – 225 | +72 | 0 | 225.072 | 225.000 | +0.072 | 0 | +0.00283 / 0 |
| 225 – 250 | +72 | 0 | 250.072 | 250.000 | +0.072 | 0 | +0.00283 / 0 |
| 250 – 280 | +81 | 0 | 280.081 | 280.000 | +0.081 | 0 | +0.00319 / 0 |
| 280 – 315 | +81 | 0 | 315.081 | 315.000 | +0.081 | 0 | +0.00319 / 0 |
| 315 – 355 | +89 | 0 | 355.089 | 355.000 | +0.089 | 0 | +0.00350 / 0 |
| 355 – 400 | +89 | 0 | 400.089 | 400.000 | +0.089 | 0 | +0.00350 / 0 |
| 400 – 450 | +97 | 0 | 450.097 | 450.000 | +0.097 | 0 | +0.00382 / 0 |
| 450 – 500 | +97 | 0 | 500.097 | 500.000 | +0.097 | 0 | +0.00382 / 0 |
Deviations at the upper end of each range (Ø columns use that size); use the calculator for the exact size. — : not defined by ISO 286 for that size. Upper/Lower (mm) and inch columns are shown on wider screens.
About H8
H8 denotes a hole tolerance zone with zero line deviation in the ISO 286 system. It is used in H8/e8 (Plain bearings in gearboxes and pumps, sliding gears, easily assembled couplings.) and H8/f7 (Accurate machines and shafts in plain bearings at moderate speeds and pressures: machine tool spindles, gearbox shafts.).
At Ø25 mm H8 is +0.033 / 0 mm, i.e. 25.000 to 25.033 mm.
How the limits are calculated
H8 uses grade IT8 (a standard tolerance of 33 µm at 18–30 mm). Fundamental deviation: EI = 0: the tolerance zone sits entirely above the nominal size, and IT8 sets its width. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.