Clearance, transition and interference fits
ISO 286 groups every hole/shaft pairing into one of three types by how their tolerance zones relate to each other — shown here at Ø25 mm.
The three types
| Type | Example | Min (mm) | Max (mm) | Typical use |
|---|---|---|---|---|
| Clearance | H7/g6 | +0.007 | +0.041 | Parts that must slide or rotate relative to each other |
| Transition | H7/k6 | −0.015 | +0.019 | Parts located accurately but assembled or removed by hand or a light press |
| Interference | H7/p6 | −0.035 | −0.001 | Parts permanently fixed together, no relative movement |
Negative = interference. Typical use is shown on wider screens.
Fit diagram (H7/g6 at Ø25 mm, µm · zero line = nominal)
Clearance fits
A clearance fit always leaves a gap: the shaft's tolerance zone sits entirely below the hole's, so the shaft fits inside the hole at every combination of sizes within tolerance, from the loosest pairing (largest hole, smallest shaft) to the tightest (smallest hole, largest shaft).
Used wherever a part must move — rotating shafts in plain bearings, sliding pins, parts assembled and disassembled repeatedly by hand.
Transition fits
A transition fit's tolerance zones overlap: depending which end of each zone the actual parts land on, the assembly can come out as a small clearance or a small interference. Neither is guaranteed.
Used for accurate location that still allows hand or light-press assembly — gears and pulleys on keyed shafts, bearing inner rings, dowelled joints.
Interference fits
An interference fit always overlaps: the shaft's tolerance zone sits entirely above the hole's, so the shaft is oversized relative to the hole at every combination within tolerance. The parts must be pressed, pulled or shrunk together.
Used for permanent joints that transmit torque or axial load without a key — pressed-in bushes, shrink-fitted gears and rings, force fits on shafts.
Enter your own size and classes in the calculator to see which type a specific pairing gives, or use the fit finder to search by clearance or interference target.