Patent ID: 7401982

Claim:
A bearing comprising: an inner race having a rotational axis; an outer race sharing the rotational axis of the inner race; a plurality of ball bearing members constrained between contact shoulders on the inner race and the outer race which are tangential to plurality of rolling bearing members, the tangential contact surfaces being oriented at a contact angle of approximately 30 degrees in relation the rotational axis, such that the ball bearing members are adapted to bear axial thrust loading in only one direction; a retention lip only sufficient to maintain a peripheral opening of a constant gauge distance of permissible bearing wear between and prevent relative axial movement of the inner race and the outer race, the gauge distance of the peripheral opening being adapted to allow free passage of the ball bearing members, when wear on the bail bearing members reaches a predetermined level, the peripheral opening also providing a flow gap between the inner race and the outer race to allow for mud lubrication; and the retention lip defining a portion of the tangential contact surface of one of the inner and the outer races, the retention lip being spaced inwardly from a side wall of the bearing and directly engaging with the plurality of ball bearing members to prevent relative movement of the inner race relative to the outer race, in one direction of movement, until at least one of the retention lip and at least some of the plurality of ball bearing members become sufficiently worn to permit such relative movement.