ANSI/ASME B18.8.1 Cotter Pin Application Size Table Chart

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Cotter Pins per ANSI/ASME B18.8.1

A cotter is a pin or wedge passing through a hole to fix parts tightly together. In British usage cotter pin has the same meaning, but in the U.S. it refers to a different fastener .

Typical applications are in fixing a crank to its crankshaft , as in a bicycle, or a piston rod to a crosshead , as in a steam engine. Note: the angle of the wedge determines the position of the parts being held, therefore on a bicycle the pedal arms will only be at 180 degrees to each other if the angle of the cotter pin's wedge is the same on both pins.

Cotter Pin Size and Dimensions

NOMINAL
SIZE
A
Diameter
C
Head Diameter
D
Prong Length
LENGTH
.03125 0.032 0.060 0.010 0.125 to 3 by 1/8
.046875 0.048 0.090 0.020 0.125 to 3 by 1/8
.0625 0.060 0.120 0.030 0.25 to 3 by 1/8
.078125 0.076 0.160 0.040 0.25 to 3 by 1/8
.09375 0.090 0.190 0.040 0.375 to 3 by 1/8
.109375 0.104 0.220 0.050 0.375 to 3 by 1/8
.125 0.120 0.250 0.060 0.5 to 3 by 1/8
.140625 0.134 0.280 0.060 0.5 to 3 by 1/8
.15625 0.150 0.310 0.070 0.625 to 3 by 1/8