An unsealed rotary drill of the type comprising a bearing shaft, a roller rotatably mounted on the shaft, cutting inserts carried by the roller, bearing for rotatably supporting the roller on the shaft, and a flushing channel terminating at an end surface of the bearing shaft for conducting cooling air to the bearing. The bearing includes an axial bearing comprising an insert plate formed of sintered hard metal alloy, and a supporting plate formed of a material which is less hard and less wear resistant than the metal alloy. The supporting plate contains a solid lubricant. The supporting plate and the insert plate present opposed bearing surfaces. The insert plate is mounted in the end surface of the bearing shaft such that a rear surface of the insert plate is acted upon by cooling air from the flushing channel.
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