H7 hole tolerance (IT7)
Capital H7 is an ISO 286 hole tolerance class (IT7, EI = 0): at Ø10 mm the deviations are +0.015/0 mm, at Ø25 mm +0.021/0 mm (upper/lower). Looking for the h7 shaft?
Hole tolerance class H7 per ISO 286-1:2010: fundamental deviation EI = 0, grade IT7 (10 µm at ≤ 3 mm to 63 µm at 400–500 mm). For an exact size, open the calculator with H7 selected.
- Type
- Hole
- Grade
- IT7
- Tolerance
- 10 … 63 µm
- Fund. deviation
- EI = 0
H7 limits by size range
| Size (mm) | Upper (µm) | Lower (µm) | Ø max (mm) | Ø min (mm) | Upper (mm) | Lower (mm) | Dev. (in) |
|---|---|---|---|---|---|---|---|
| ≤ 3 | +10 | 0 | 3.010 | 3.000 | +0.010 | 0 | +0.00039 / 0 |
| 3 – 6 | +12 | 0 | 6.012 | 6.000 | +0.012 | 0 | +0.00047 / 0 |
| 6 – 10 | +15 | 0 | 10.015 | 10.000 | +0.015 | 0 | +0.00059 / 0 |
| 10 – 14 | +18 | 0 | 14.018 | 14.000 | +0.018 | 0 | +0.00071 / 0 |
| 14 – 18 | +18 | 0 | 18.018 | 18.000 | +0.018 | 0 | +0.00071 / 0 |
| 18 – 24 | +21 | 0 | 24.021 | 24.000 | +0.021 | 0 | +0.00083 / 0 |
| 24 – 30 | +21 | 0 | 30.021 | 30.000 | +0.021 | 0 | +0.00083 / 0 |
| 30 – 40 | +25 | 0 | 40.025 | 40.000 | +0.025 | 0 | +0.00098 / 0 |
| 40 – 50 | +25 | 0 | 50.025 | 50.000 | +0.025 | 0 | +0.00098 / 0 |
| 50 – 65 | +30 | 0 | 65.030 | 65.000 | +0.030 | 0 | +0.00118 / 0 |
| 65 – 80 | +30 | 0 | 80.030 | 80.000 | +0.030 | 0 | +0.00118 / 0 |
| 80 – 100 | +35 | 0 | 100.035 | 100.000 | +0.035 | 0 | +0.00138 / 0 |
| 100 – 120 | +35 | 0 | 120.035 | 120.000 | +0.035 | 0 | +0.00138 / 0 |
| 120 – 140 | +40 | 0 | 140.040 | 140.000 | +0.040 | 0 | +0.00157 / 0 |
| 140 – 160 | +40 | 0 | 160.040 | 160.000 | +0.040 | 0 | +0.00157 / 0 |
| 160 – 180 | +40 | 0 | 180.040 | 180.000 | +0.040 | 0 | +0.00157 / 0 |
| 180 – 200 | +46 | 0 | 200.046 | 200.000 | +0.046 | 0 | +0.00181 / 0 |
| 200 – 225 | +46 | 0 | 225.046 | 225.000 | +0.046 | 0 | +0.00181 / 0 |
| 225 – 250 | +46 | 0 | 250.046 | 250.000 | +0.046 | 0 | +0.00181 / 0 |
| 250 – 280 | +52 | 0 | 280.052 | 280.000 | +0.052 | 0 | +0.00205 / 0 |
| 280 – 315 | +52 | 0 | 315.052 | 315.000 | +0.052 | 0 | +0.00205 / 0 |
| 315 – 355 | +57 | 0 | 355.057 | 355.000 | +0.057 | 0 | +0.00224 / 0 |
| 355 – 400 | +57 | 0 | 400.057 | 400.000 | +0.057 | 0 | +0.00224 / 0 |
| 400 – 450 | +63 | 0 | 450.063 | 450.000 | +0.063 | 0 | +0.00248 / 0 |
| 450 – 500 | +63 | 0 | 500.063 | 500.000 | +0.063 | 0 | +0.00248 / 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 H7
H7 denotes a hole tolerance zone with zero line deviation in the ISO 286 system. It is used in H7/f7 (Sliding parts and journals at moderate speeds with noticeable but small play.) and H7/g6 (Precision sliding parts that must move without perceptible play: spindles, sliding gears, guide pins, plungers.).
At Ø25 mm H7 is +0.021 / 0 mm, i.e. 25.000 to 25.021 mm.
How the limits are calculated
H7 uses grade IT7 (a standard tolerance of 21 µm at 18–30 mm). Fundamental deviation: EI = 0: the tolerance zone sits entirely above the nominal size, and IT7 sets its width. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.
H7 in practice
Where it's used
H7 is the default bore of the hole-basis system: most fits on a drawing pair an H7 hole with whichever shaft class sets the fit. Typical H7 bores are gear, pulley and coupling hubs (with h6, k6 or m6 shafts), holes for hardened dowel pins (made to m6), and housing bores for bearings whose outer ring must be free to float axially. IT7 is beyond a twist drill: plan on reaming, fine boring or grinding.
How to check it
In production, use a GO/NO-GO plug gauge. The GO end is the nominal size and must enter the full length of the bore; the NO-GO end is the upper limit and must not enter. H7 plug gauges are stock items for every common size. For measured values, use a three-point internal micrometer or a dial bore gauge set on a ring gauge. Measure at the 20 °C reference temperature of ISO 1: a warm part straight off the machine reads oversize.
Easily confused with
h7 in lower case is a shaft class whose zone sits below the nominal size, the mirror image of H7. H7 on its own is not a fit: the shaft class decides whether you get clearance, transition or interference. Since ISO 286-1:2010 a size tolerance does not control form either; if the bore must also be round and straight within the size limits, add the envelope requirement Ⓔ.
Worked example
A 6208 deep-groove ball bearing has an 80 mm outside diameter. Its housing bore, drawn as Ø80 H7, measures 80.000–80.030 mm (+0.030/0 mm), so the GO plug is 80.000 mm and the NO-GO plug 80.030 mm.