Tolerance chart
H9 tolerance (hole): ISO 286 chart up to 500 mm
H9 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means +52 / 0 µm: the size may lie between 25.000 and 25.052 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use H9.
H9 chart: deviations for all nominal sizes up to 500 mm
Deviations in µm (1 µm = 0.001 mm). A nominal size belongs to the row »over … up to and including …«: exactly 30 mm is in the row ending at 30, 30.1 mm in the next one.
| Nominal size over – to (mm) | Upper deviation | Lower deviation | Tolerance |
|---|---|---|---|
| 0 – 3 | +25 | 0 | 25 |
| 3 – 6 | +30 | 0 | 30 |
| 6 – 10 | +36 | 0 | 36 |
| 10 – 18 | +43 | 0 | 43 |
| 18 – 30 | +52 | 0 | 52 |
| 30 – 50 | +62 | 0 | 62 |
| 50 – 80 | +74 | 0 | 74 |
| 80 – 120 | +87 | 0 | 87 |
| 120 – 180 | +100 | 0 | 100 |
| 180 – 250 | +115 | 0 | 115 |
| 250 – 315 | +130 | 0 | 130 |
| 315 – 400 | +140 | 0 | 140 |
| 400 – 500 | +155 | 0 | 155 |
H9 for your nominal size
How H9 is built
An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter H sets the position of the tolerance zone; at Ø25 mm it lies from the nominal size upwards: the hole is never smaller than nominal. The number 9 is the standard tolerance grade IT9: it sets how wide the zone is – 52 µm at Ø25 mm.
The tolerance grows with the nominal size: 25 µm in the smallest row (0 – 3 mm), 155 µm in the largest (400 – 500 mm). On a drawing the class follows the dimension, as in »Ø25 H9«; the inspection plan turns that into the limits 25.000 and 25.052 mm.
Fits with H9 at Ø25 mm
Hole-basis system: the hole stays H9, the shaft changes. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.
| Fit | Type | Max. clearance | Min. clearance |
|---|---|---|---|
| H9/d9 | clearance fit | 169 | 65 |
| H9/e8 | clearance fit | 125 | 40 |
| H9/h8 | clearance fit | 85 | 0 |
| H9/h9 | clearance fit | 104 | 0 |
Frequently asked questions about H9
What does H9 mean?
H9 is an ISO tolerance class for holes (internal features): the letter H sets the position of the tolerance zone, the number 9 the standard tolerance grade IT9. At Ø25 mm that gives +52 / 0 µm, i.e. 25.000 to 25.052 mm.
What are the H9 limits at Ø10 and Ø50 mm?
Ø10 H9: +36 / 0 µm (10.000 to 10.036 mm). Ø50 H9: +62 / 0 µm (50.000 to 50.062 mm).
Is H9 a clearance fit?
A tolerance class on its own is not a fit – only together with its mating part. H9/d9 at Ø25 mm is a clearance fit (maximum clearance 169 µm, minimum clearance 65 µm; a minus means interference).
More tolerance classes
Same letter H, other grades: H6 · H7 · H8 · H10 · H11
All classes at a glance: ISO 286 tolerance charts. The same chart in German: H9 Toleranz.