Abstract: A cap driver for supporting a cap holder on an embroidery machine has a cylindrical shell that is yieldably biasedly supported on support rollers and guided during rotation by guide wheels that are rotatably attached to one end of a pivotable arm that allows the guide wheels, and cylindrical shell, to ride over obstructions that may occur during rotation of the shell. The guide wheels mate with a rail that has a surface elevated above the outer surface of the shell. The cap driver overcomes the problem of fixed support and guide wheels that previously caused distortion of the cylindrical shell when obstructions were encountered during rotation. Also, the present invention overcomes the problem of debris buildup in a circumferential guide groove on the outer surface of the shell.