Abstract: A first embodiment of a radially disposed thrust bearing assembly for rotary cone rock bits consists of a first non-rotating radially disposed steel thrust bearing disc and an adjacent, carbide thrust bearing disc. One of the thrust bearing discs is pressed into a disc retention socket formed in the end of a spindle bearing extending from the end of a main axially aligned bearing cantilevered from a leg of the bit and the other thrust bearing disc is pressed into a disc retention socket formed in the rotary cone. An edge of the carbide disc is formed with large valleys and peaks, the robust undulations resist cracking when the carbide thrust bearing disc is pressed into its respective socket. Unique air passages and channels are formed in the main and spindle bearings to direct cooling air to the thrust bearing discs.