Below is a calculator that I created in order to calculate the diametral clearance encountered when trying to assemble a shaft into a part with a bore (hole).
Tips on Diametral Clearances
This is one of the most common and simple calculations that a designer must do in order to ensure ease of assembly and control critical areas of a machine that will need precise alignment. Clearances will also control the radial tolerance stackup of parts and needs to be attended to so that there will be no assembly issues. A designer should also consider the thermal growth and shrinkage of parts based on material properties during a machine's operation. A good engineer will understand as much as he/she can about the process conditions in order to proper material selection for their parts. A close and tight fit could come apart under operating conditions and become a loose fit due to thermal effects, which may lead to complete failure of a machine.
For example, the Rotor Assemblies and Bullgear Assemblies of an Integrally Geared Centrifugal Compressor (IGC) will need to use tight radial clearances with the fluid film bearings supporting these assemblies. The Impeller/Wheel and Shroud radial clearance of a Centrifugal Compressor or a Turboexpander is one the most critical clearances that is also held to a close clearance and takes into account the axial end play of a machine. Any change to this clearance may reduce the overall machine efficiency drastically, and its effect is relative to size. Therefore, the smaller the machine is, the tighter the clearance, and thus the more effect on efficiency that a clearance has.
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