What Is The Tolerance Fit?

Refers to the sum of the tolerances of the holes and shafts that make up the fit.  Represents the allowable variation range of the fit tightness. Because the actual size of hole and shaft is different, “clearance” or “interference” can be generated after assembly.

There are three types of tolerance fits: clearance fit, transition fit and interference fit.

Clearance fit: refers to the fit with clearance (including the minimum clearance equal to zero). The tolerance zone of the hole is above the tolerance zone of the shaft, the actual size of the hole is always greater than or equal to the actual size of the shaft. There is an obvious clearance between the shaft and the hole, and the shaft can rotate in the hole.

Interference fit: refers to the fit with interference (including minimum interference equal to zero). The tolerance zone of the hole is below the tolerance zone of the shaft. There is no clearance between the shaft and hole, the shaft and the hole are tightly connected together, the shaft will not be able to rotate alone.

Transition fit means that there may be clearance fit or interference fit when the hole is assembled with the shaft, and the tolerance zone of the hole and the tolerance zone of the shaft overlap each other. This fit can be used as a precision positioning fit.