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Clearance and interference coupling fits: Tips on when to use and how to determine tolerances

Publication date: 
July 2009
Tom Bishop, P.E., EASA Senior Technical Support Specialist
Type of media: 

Couplings for connecting shafts can be placed in two categories: keyed and keyless. Similarly, the fits of couplings to shafts can be categorized as clearance or interference. A keyless coupling arrangement will always have an interference fit, while a keyed arrangement may have either a clearance or an interference fit. This article will focus on determining when to use a clearance or an interference fit, and how to obtain the tolerances for the resulting fit.