A
universal joint, (
universal coupling,
U-joint,
Cardan joint,
Hardy-Spicer joint, or
Hooke's joint) is a
joint or
coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit
rotary motion. It consists of a pair of
hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a
constant-velocity joint.