Tolerance chart
N6 tolerance (hole): ISO 286 chart up to 500 mm
N6 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means −11 / −24 µm: the size may lie between 24.976 and 24.989 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use N6.
N6 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 | −4 | −10 | 6 |
| 3 – 6 | −5 | −13 | 8 |
| 6 – 10 | −7 | −16 | 9 |
| 10 – 18 | −9 | −20 | 11 |
| 18 – 30 | −11 | −24 | 13 |
| 30 – 50 | −12 | −28 | 16 |
| 50 – 80 | −14 | −33 | 19 |
| 80 – 120 | −16 | −38 | 22 |
| 120 – 180 | −20 | −45 | 25 |
| 180 – 250 | −22 | −51 | 29 |
| 250 – 315 | −25 | −57 | 32 |
| 315 – 400 | −26 | −62 | 36 |
| 400 – 500 | −27 | −67 | 40 |
N6 for your nominal size
How N6 is built
An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter N sets the position of the tolerance zone; at Ø25 mm it lies entirely below the nominal size: the hole is always smaller than nominal. The number 6 is the standard tolerance grade IT6: it sets how wide the zone is – 13 µm at Ø25 mm.
The tolerance grows with the nominal size: 6 µm in the smallest row (0 – 3 mm), 40 µm in the largest (400 – 500 mm). On a drawing the class follows the dimension, as in »Ø25 N6«; the inspection plan turns that into the limits 24.976 and 24.989 mm.
Fits with N6 at Ø25 mm
Shaft-basis system: the shaft is h, the hole N6. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.
Frequently asked questions about N6
What does N6 mean?
N6 is an ISO tolerance class for holes (internal features): the letter N sets the position of the tolerance zone, the number 6 the standard tolerance grade IT6. At Ø25 mm that gives −11 / −24 µm, i.e. 24.976 to 24.989 mm.
What are the N6 limits at Ø10 and Ø50 mm?
Ø10 N6: −7 / −16 µm (9.984 to 9.993 mm). Ø50 N6: −12 / −28 µm (49.972 to 49.988 mm).
Is N6 a clearance fit?
A tolerance class on its own is not a fit – only together with its mating part. N6/h5 at Ø25 mm is a interference fit (maximum clearance −2 µm, minimum clearance −24 µm; a minus means interference).
More tolerance classes
Same letter N, other grades: N7
Holes in grade 6: H6 · G6 · JS6 · K6 · M6 · P6
All classes at a glance: ISO 286 tolerance charts. The same chart in German: N6 Toleranz.