Fits & limits (ISO 286)
For a 25 mm shaft in an H7/g6 sliding fit, the hole runs +0 / +21 µm and the shaft −7 / −20 µm, giving 7–41 µm of clearance. This page computes ISO 286 limit deviations for any nominal size and hole/shaft tolerance class, and tells you whether the pair is a clearance, transition, or interference fit.
Enter a nominal diameter and designations like H7 and g6, or click a preferred fit to load it. Deviations are shown in µm and as absolute limits in mm.
Ø 25 H7/g6
A negative clearance is interference.
- Resulting fit
- Clearance · +7 to +41 µm
- Hole H7
- +21 / +0 µm
- Hole H7, max / min
- Shaft g6
- -7 / -20 µm
- Shaft g6, max / min
How it’s calculated
Each limit is the nominal plus its ISO 286 deviation: the fundamental deviation sets the zone's position, the IT grade its width. The largest clearance is the hole's upper limit less the shaft's lower, the smallest the hole's lower less the shaft's upper: both positive is a clearance fit, both negative an interference, one of each a transition.
Across size ranges
| Nominal (mm) | Hole H7 (µm) | Shaft g6 (µm) |
|---|---|---|
| ≤ 3 | +10 / +0 | -2 / -8 |
| > 3 to 6 | +12 / +0 | -4 / -12 |
| > 6 to 10 | +15 / +0 | -5 / -14 |
| > 10 to 18 | +18 / +0 | -6 / -17 |
| > 18 to 30 | +21 / +0 | -7 / -20 |
| > 30 to 50 | +25 / +0 | -9 / -25 |
| > 50 to 80 | +30 / +0 | -10 / -29 |
| > 80 to 120 | +35 / +0 | -12 / -34 |
| > 120 to 180 | +40 / +0 | -14 / -39 |
| > 180 to 250 | +46 / +0 | -15 / -44 |
| > 250 to 315 | +52 / +0 | -17 / -49 |
| > 315 to 400 | +57 / +0 | -18 / -54 |
| > 400 to 500 | +63 / +0 | -20 / -60 |
Preferred fits (ASME B4.2 Table 6-1)
| Fit | Basis | Type | Application |
|---|---|---|---|
| H11/c11 | Hole | clearance | Loose running: wide commercial tolerances or allowances on external members |
| C11/h11 | Shaft | clearance | Loose running: wide commercial tolerances or allowances on external members |
| H9/d9 | Hole | clearance | Free running: not where accuracy is essential; large temperature variations, high running speeds or heavy journal pressures |
| D9/h9 | Shaft | clearance | Free running: not where accuracy is essential; large temperature variations, high running speeds or heavy journal pressures |
| H8/f7 | Hole | clearance | Close running: accurate machines, accurate location at moderate speeds and journal pressures |
| F8/h7 | Shaft | clearance | Close running: accurate machines, accurate location at moderate speeds and journal pressures |
| H7/g6 | Hole | clearance | Sliding: not to run freely, but to move and turn freely and locate accurately |
| G7/h6 | Shaft | clearance | Sliding: not to run freely, but to move and turn freely and locate accurately |
| H7/h6 | Hole and shaft | clearance | Locational clearance: snug fit for locating stationary parts, freely assembled and disassembled |
| H7/k6 | Hole | transition | Locational transition: accurate location, a compromise between clearance and interference |
| K7/h6 | Shaft | transition | Locational transition: accurate location, a compromise between clearance and interference |
| H7/n6 | Hole | transition | Locational transition: more accurate location where greater interference is permissible |
| N7/h6 | Shaft | transition | Locational transition: more accurate location where greater interference is permissible |
| H7/p6 | Hole | interferenceTransition fit for nominal sizes 0 to 3 mm (ASME B4.2 Table 6-1, note 1). | Locational interference: rigidity and alignment with prime accuracy of location, without special bore pressure requirements |
| P7/h6 | Shaft | interference | Locational interference: rigidity and alignment with prime accuracy of location, without special bore pressure requirements |
| H7/s6 | Hole | interference | Medium drive: ordinary steel parts or shrink fits on light sections; the tightest fit usable with cast iron |
| S7/h6 | Shaft | interference | Medium drive: ordinary steel parts or shrink fits on light sections; the tightest fit usable with cast iron |
| H7/u6 | Hole | interference | Force: parts that can be highly stressed, or shrink fits where the heavy pressing forces required are impractical |
| U7/h6 | Shaft | interference | Force: parts that can be highly stressed, or shrink fits where the heavy pressing forces required are impractical |
What do H7 and g6 mean?
An ISO 286 tolerance class combines a fundamental deviation (a letter — its position relative to the nominal size) with a tolerance grade (a number, IT01–IT18 — the width of the tolerance zone). Upper-case letters (H, G, F) are holes; lower-case (h, g, f) are shafts.
So H7 is a hole whose lower limit sits exactly on the nominal size with an IT7-wide zone above it, and g6 is a shaft sitting just below nominal with an IT6-wide zone. The grade width scales with nominal size, which is why the deviations change across the size-range table above.
How is the type of fit determined?
Clearance is hole − shaft. The minimum clearance is the hole’s lower limit minus the shaft’s upper limit; the maximum clearance is the hole’s upper limit minus the shaft’s lower limit. If both are positive the pair always has clearance; if both are negative it is always interference; if the range straddles zero it is a transition fit.