Caster thread guard and caster assembly

A caster includes a yoke having a yoke leg with a yoke leg axle opening through the yoke leg. A wheel having a hub and a hub axle opening through the hub is attached to the yoke leg with an axle bolt. A thread guard is located between the hub and the yoke leg. The thread guard has a disk-shaped body with a thread guard axle opening through the body for receiving the axle bolt. The thread guard further includes an outer surface facing toward the yoke leg and an inner surface facing toward the hub, and the outer surface includes a raised ridge extending away from the body. The ridge substantially surrounds and conforms to the shape of the yoke leg. The ridge preferably extends from the body past the outer surface of the yoke leg.