ISO 286 limits and fits
The drawing says "Ø25 k6" — what size do you turn? Enter the diameter and the tolerance class to get the deviations, limits and the middle of the zone. For a fit — the clearance or interference.
Quick answer
Ø25 k6 = +0.015 / +0.002 mm, so the shaft is 25.002–25.015 mm (mid-zone 25.0085). A Ø25 H7 hole is 25.000–25.021 mm. H7/k6 is a transition fit: from 0.019 mm clearance to 0.015 mm interference.
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- Deviations
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- Max
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- Min
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- Mid-zone
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- Deviations
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- Max
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- Min
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- Mid-zone
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A capital letter is a hole, a small letter a shaft. The letter places the zone relative to the nominal (H — from zero up, h — from zero down, k, n, p, s — above zero), the number is the grade, i.e. the zone width: the smaller, the tighter.
Aim for the middle of the zone, not the edge: that leaves room for tool wear, part heating and measuring error.
Common fits
| H7/h6 | locational clearance, accurate location |
| H7/g6 | sliding, parts move and turn freely |
| H8/f7 | close running, plain bearings |
| H7/js6 | transition, easy assembly |
| H7/k6 | transition, gears, pulleys, couplings |
| H7/n6 | transition, tighter |
| H7/p6 | light press fit |
| H7/s6 | medium drive fit |
H7 and common shaft deviations, µm
| Size, mm | H7 | g6 | h6 | js6 | k6 | n6 | p6 | s6 |
|---|---|---|---|---|---|---|---|---|
| 0–3 | +10 0 | −2 −8 | 0 −6 | +3 −3 | +6 0 | +10 +4 | +12 +6 | +20 +14 |
| 3–6 | +12 0 | −4 −12 | 0 −8 | +4 −4 | +9 +1 | +16 +8 | +20 +12 | +27 +19 |
| 6–10 | +15 0 | −5 −14 | 0 −9 | +5 −5 | +10 +1 | +19 +10 | +24 +15 | +32 +23 |
| 10–14 | +18 0 | −6 −17 | 0 −11 | +6 −6 | +12 +1 | +23 +12 | +29 +18 | +39 +28 |
| 14–18 | +18 0 | −6 −17 | 0 −11 | +6 −6 | +12 +1 | +23 +12 | +29 +18 | +39 +28 |
| 18–24 | +21 0 | −7 −20 | 0 −13 | +7 −7 | +15 +2 | +28 +15 | +35 +22 | +48 +35 |
| 24–30 | +21 0 | −7 −20 | 0 −13 | +7 −7 | +15 +2 | +28 +15 | +35 +22 | +48 +35 |
| 30–40 | +25 0 | −9 −25 | 0 −16 | +8 −8 | +18 +2 | +33 +17 | +42 +26 | +59 +43 |
| 40–50 | +25 0 | −9 −25 | 0 −16 | +8 −8 | +18 +2 | +33 +17 | +42 +26 | +59 +43 |
| 50–65 | +30 0 | −10 −29 | 0 −19 | +10 −10 | +21 +2 | +39 +20 | +51 +32 | +72 +53 |
| 65–80 | +30 0 | −10 −29 | 0 −19 | +10 −10 | +21 +2 | +39 +20 | +51 +32 | +78 +59 |
| 80–100 | +35 0 | −12 −34 | 0 −22 | +11 −11 | +25 +3 | +45 +23 | +59 +37 | +93 +71 |
| 100–120 | +35 0 | −12 −34 | 0 −22 | +11 −11 | +25 +3 | +45 +23 | +59 +37 | +101 +79 |
| 120–140 | +40 0 | −14 −39 | 0 −25 | +13 −13 | +28 +3 | +52 +27 | +68 +43 | +117 +92 |
| 140–160 | +40 0 | −14 −39 | 0 −25 | +13 −13 | +28 +3 | +52 +27 | +68 +43 | +125 +100 |
| 160–180 | +40 0 | −14 −39 | 0 −25 | +13 −13 | +28 +3 | +52 +27 | +68 +43 | +133 +108 |
| 180–200 | +46 0 | −15 −44 | 0 −29 | +15 −15 | +33 +4 | +60 +31 | +79 +50 | +151 +122 |
| 200–225 | +46 0 | −15 −44 | 0 −29 | +15 −15 | +33 +4 | +60 +31 | +79 +50 | +159 +130 |
| 225–250 | +46 0 | −15 −44 | 0 −29 | +15 −15 | +33 +4 | +60 +31 | +79 +50 | +169 +140 |
| 250–280 | +52 0 | −17 −49 | 0 −32 | +16 −16 | +36 +4 | +66 +34 | +88 +56 | +190 +158 |
| 280–315 | +52 0 | −17 −49 | 0 −32 | +16 −16 | +36 +4 | +66 +34 | +88 +56 | +202 +170 |
| 315–355 | +57 0 | −18 −54 | 0 −36 | +18 −18 | +40 +4 | +73 +37 | +98 +62 | +226 +190 |
| 355–400 | +57 0 | −18 −54 | 0 −36 | +18 −18 | +40 +4 | +73 +37 | +98 +62 | +244 +208 |
| 400–450 | +63 0 | −20 −60 | 0 −40 | +20 −20 | +45 +5 | +80 +40 | +108 +68 | +272 +232 |
| 450–500 | +63 0 | −20 −60 | 0 −40 | +20 −20 | +45 +5 | +80 +40 | +108 +68 | +292 +252 |
Values are ISO 286-2 per the tables of the US metric standard ANSI B4.2, which is based on ISO 286. The data was checked automatically: every zone's deviation spread equals the IT tolerance, and the fundamental deviation of each letter is the same across grades. Sizes up to 500 mm; ranges are "over … up to and including …".