Taper pin

A taper pin is a fastener used in mechanical engineering. They are steel rods with one end having a slightly larger diameter than the other. Standard inch-sized taper pins have a taper on diameter of 1:48 while metric ones have a taper of 1:50. A 1:48 taper means that one end of a 4-foot-long bar (48 inches) will be 1 inch smaller in diameter than the other end, or a 1/4-inch taper over a 1-foot length.