Tolerance chart
F8 tolerance (hole): ISO 286 chart up to 500 mm
F8 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means +53 / +20 µm: the size may lie between 25.020 and 25.053 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use F8.
F8 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 | +20 | +6 | 14 |
| 3 – 6 | +28 | +10 | 18 |
| 6 – 10 | +35 | +13 | 22 |
| 10 – 18 | +43 | +16 | 27 |
| 18 – 30 | +53 | +20 | 33 |
| 30 – 50 | +64 | +25 | 39 |
| 50 – 80 | +76 | +30 | 46 |
| 80 – 120 | +90 | +36 | 54 |
| 120 – 180 | +106 | +43 | 63 |
| 180 – 250 | +122 | +50 | 72 |
| 250 – 315 | +137 | +56 | 81 |
| 315 – 400 | +151 | +62 | 89 |
| 400 – 500 | +165 | +68 | 97 |
F8 for your nominal size
How F8 is built
An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter F sets the position of the tolerance zone; at Ø25 mm it lies entirely above the nominal size: the hole is always larger than nominal. The number 8 is the standard tolerance grade IT8: it sets how wide the zone is – 33 µm at Ø25 mm.
The tolerance grows with the nominal size: 14 µm in the smallest row (0 – 3 mm), 97 µm in the largest (400 – 500 mm). On a drawing the class follows the dimension, as in »Ø25 F8«; the inspection plan turns that into the limits 25.020 and 25.053 mm.
Fits with F8 at Ø25 mm
Shaft-basis system: the shaft is h, the hole F8. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.
Frequently asked questions about F8
What does F8 mean?
F8 is an ISO tolerance class for holes (internal features): the letter F sets the position of the tolerance zone, the number 8 the standard tolerance grade IT8. At Ø25 mm that gives +53 / +20 µm, i.e. 25.020 to 25.053 mm.
What are the F8 limits at Ø10 and Ø50 mm?
Ø10 F8: +35 / +13 µm (10.013 to 10.035 mm). Ø50 F8: +64 / +25 µm (50.025 to 50.064 mm).
Is F8 a clearance fit?
A tolerance class on its own is not a fit – only together with its mating part. F8/h7 at Ø25 mm is a clearance fit (maximum clearance 74 µm, minimum clearance 20 µm; a minus means interference).
More tolerance classes
Same letter F, other grades: F7
All classes at a glance: ISO 286 tolerance charts. The same chart in German: F8 Toleranz.