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Cotterless Cranks
The modern type of three-piece crankset. Although one-piece cranks don't use cotters either, the term "cotterless" normally refers to two-piece or three-piece sets.
The bottom bracket spindle (axle) used with a standard cotterless crank has tapered square ends, which fit into matching tapered square holes in the cranks. The ends of the axle have either external or internal threading, and a bolt or nut (called the "fixing" bolt/nut) pulls the crank tightly onto the end of the axle.
The nut or bolt head is recessed into the crank, in a hole with threaded sides. These threads can hold a decorative cap that hides the fixing bolt/nut, but their main function it to provide a purchase for the "crank puller", a special tool that is needed to remove the crank from the axle.
See my Tool Tips article on Cotterless Cranks
See also the Bottom Bracket entry in this Glossary. *****
