⌀40 H7/g6: Clearance fit
| Upper | Lower | Size limits (mm) | |
|---|---|---|---|
| Hole H7 | +25 µm | 0 µm | 40.000 – 40.025(1.5748 – 1.5758 inch) |
| Shaft g6 | -9 µm | -25 µm | 39.975 – 39.991(1.5738 – 1.5744 inch) |
Clearance from 9 µm to 50 µm.
Hole-basis system (H holes), ISO 286, sizes up to 500 mm. 1 µm = 0.001 mm.
Common fits and what they are for
| Fit | At 40 mm (µm) | Use |
|---|---|---|
| H11/d11 | +80 to +400 | Loose running: wide clearance, for rough work or where dirt gets in |
| H9/d9 | +80 to +204 | Free running: large temperature changes, high speeds |
| H8/f7 | +25 to +89 | Close running: shafts in plain bearings, gearbox shafts |
| H7/g6 | +9 to +50 | Sliding: parts that slide and turn accurately, locating pins |
| H7/h6 | +0 to +41 | Locating clearance: parts assembled by hand, accurate location |
| H7/k6 | -18 to +23 | Locating transition: gears and pulleys on shafts, light press |
| H7/n6 | -33 to +8 | Locating transition, firmer: needs a press, for accurate location |
| H7/p6 | -42 to -1 | Locating interference: press fit, parts held without turning |
| H7/s6 | -59 to -18 | Medium drive fit: bushes in housings, shrink fits in cast iron |
Positive numbers are clearance, negative numbers interference.
How to read a fit
- The capital letter is the hole, the small letter the shaft: H7/g6 = hole H7, shaft g6
- Hole-basis: the hole is H (it starts exactly at the nominal size) and the shaft is chosen for the fit
- Clearance fit: always a gap. Transition fit: a gap or a slight press. Interference fit: always a press
- Ground or reamed holes are usually H7; turned and ground shafts usually grade 6
Questions
- What is the tolerance of H7 at 25 mm?
- H7 for a 25 mm (0.984 inch) hole is +0.021 / 0 mm (0.00 inch): the hole may be from 25.000 to 25.021 mm (0.985 inch). H7 at 40 mm (1.57 inch) is +0.025 / 0 mm (0.00 inch).
- What is the difference between H7/h6 and H7/g6?
- Both are clearance fits. H7/h6 has zero minimum clearance, for parts located accurately and assembled by hand. H7/g6 always leaves a small gap (9 µm at 40 mm (1.57 inch)) so the parts can slide and turn.
- Which fit is a press fit?
- H7/p6 is the usual light press (locating interference) fit, and H7/s6 is a medium drive fit. H7/k6 and H7/n6 are transition fits: they may have a little clearance or a little interference.
- What does the letter and the number mean?
- The letter places the tolerance band (H means the hole's lower limit is exactly the nominal size; g, f, e sit below for clearance; k, n, p, s sit above for interference). The number is the IT grade: the larger it is, the wider the tolerance.
Need parts to these limits? See cylindrical grinding, VMC milling and drilling, boring and tapping.
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Get startedValues from the ISO 286-1 tables. Always check critical fits against the standard or your drawing.