Design Engineering

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Flip The Normal
August 17, 2021 at 1:00pm EST

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MISUMI USA – Shaft Tolerance & Fits

A ‘tolerance’ is the allowable amount of variation from a specified dimension. When tolerances are combined between a shaft and bore, they can be classified into three categories known as ‘Fits’. The Clearance [Fit], Interference [Fit], and Transition [Fit] can either assist in assembly, or prevent them from being disassembled easily. A Clearance fit ensures a shaft can be freely inserted into the intended bore. This generally means the maximum limit of the shaft is less than the minimum limit of the bore diameter. An Interference fit guarantees the shaft and bore will interfere at every point within their tolerance zone. This is commonly referred to as a ‘Press Fit’. Often the two components must be joined by excessive force, or by altering the atmospheric temperature to slightly expand or shrink the diameter for assembly. The Transition fit is a combination between the Clearance and Interference Fit. Depending on the actual dimension of the shaft and bore, it is possible that either could occur. This fit is best used when a shaft must be held in a precise location. If interference should occur, it will not be to the extent where disassembly is overly difficult.

More information here,