Engineering tool · ISO 286-1
Fit calculator.
Fits and tolerances between shaft and hole according to ISO 286: combine the two classes and discover if they mount with clearance, transition, or interference.
Fit and tolerance table: clearance, transition, and interference
| Fit | What happens when assembling | Examples |
|---|---|---|
| With clearance | The shaft is always smaller than the hole. It rotates or slides. The smaller the clearance, the more precise the guide. | H11/c11 · H9/d9 · H8/f7 · H7/g6 · H7/h6 |
| Transition | Depending on the actual dimensions, there may be a slight clearance or a slight interference. Hand assembly or light tapping. | H7/js6 · H7/k6 · H7/m6 · H7/n6 |
| With interference | The shaft is always larger than the hole. Press fit or shrink fit. Joins without keys or screws. | H7/p6 · H7/r6 · H7/s6 · H7/u6 |
Hole-basis or shaft-basis system
In the hole-basis system, the hole is always H, and the shaft position (g, h, k, p…) is selected to achieve the fit. This is the most common because custom shafts are easier to machine than holes: we recommend it for CNC machining at Proto&Go!. In the shaft-basis system, the shaft is h and the hole varies (G, H, K, P…): useful when a single calibrated shaft fits multiple parts.
Tips before dimensioning
- Request tight tolerances only for functional dimensions. Higher precision levels increase machining costs.
- Specify the complete fit on the drawing (for example
Ø25 H7/g6) and indicate which part each tolerance corresponds to.
What does the H7/g6 fit mean and what is the clearance for a 25 mm diameter?
H7/g6 is a clearance fit: the g6 shaft is smaller than the H7 hole for the same nominal diameter. At Ø25 mm, the diametral clearance ranges from 7 to 41 µm, that is, from 0.007 to 0.041 mm. For another diameter, recalculate the limits of both parts.
What is the difference between a clearance fit, an interference fit, and a transition fit?
In a clearance fit, the hole is equal to or larger than the shaft. In an interference fit, the shaft is equal to or larger than the hole, and assembly may require pressure or a temperature difference. In a transition fit, clearance or interference may occur depending on the actual measurements. Parts with the same nominal size are always compared.
What is the hole-basis system and how is the shaft fit selected?
In the hole-basis system, a hole with H tolerance position is maintained, and the shaft tolerance is selected to obtain the required fit. For example, H7/g6 provides clearance, H7/k6 may provide clearance or interference, and H7/p6 provides interference for a nominal diameter of 25 mm. The choice depends on how the joint must function and be assembled.