Tolerance chart
K6 tolerance (hole): ISO 286 chart up to 500 mm
K6 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means +2 / −11 µm: the size may lie between 24.989 and 25.002 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use K6.
K6 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 | 0 | −6 | 6 |
| 3 – 6 | +2 | −6 | 8 |
| 6 – 10 | +2 | −7 | 9 |
| 10 – 18 | +2 | −9 | 11 |
| 18 – 30 | +2 | −11 | 13 |
| 30 – 50 | +3 | −13 | 16 |
| 50 – 80 | +4 | −15 | 19 |
| 80 – 120 | +4 | −18 | 22 |
| 120 – 180 | +4 | −21 | 25 |
| 180 – 250 | +5 | −24 | 29 |
| 250 – 315 | +5 | −27 | 32 |
| 315 – 400 | +7 | −29 | 36 |
| 400 – 500 | +8 | −32 | 40 |
K6 for your nominal size
How K6 is built
An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter K sets the position of the tolerance zone; at Ø25 mm it lies on both sides of the nominal size. 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 K6«; the inspection plan turns that into the limits 24.989 and 25.002 mm.
Fits with K6 at Ø25 mm
Shaft-basis system: the shaft is h, the hole K6. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.
Frequently asked questions about K6
What does K6 mean?
K6 is an ISO tolerance class for holes (internal features): the letter K sets the position of the tolerance zone, the number 6 the standard tolerance grade IT6. At Ø25 mm that gives +2 / −11 µm, i.e. 24.989 to 25.002 mm.
What are the K6 limits at Ø10 and Ø50 mm?
Ø10 K6: +2 / −7 µm (9.993 to 10.002 mm). Ø50 K6: +3 / −13 µm (49.987 to 50.003 mm).
Is K6 a clearance fit?
A tolerance class on its own is not a fit – only together with its mating part. K6/h5 at Ø25 mm is a transition fit (maximum clearance 11 µm, minimum clearance −11 µm; a minus means interference).
More tolerance classes
Same letter K, other grades: K7
Holes in grade 6: H6 · G6 · JS6 · M6 · N6 · P6
All classes at a glance: ISO 286 tolerance charts. The same chart in German: K6 Toleranz.