Lubricant is circulated from a lubricant reservoir to the bearings of a rotary rock bit and back to the lubricant reservoir by a lubricant circulation system that is operated by rotation of the cone cutter upon the bearing pin of the bit. A seal is positioned between the rolling cone cutter and the arm of the bit to maintain lubricant in the bearing area and to prevent fluid in the borehole from entering the bearing area. A lubricant reservoir is located in the bit body. A first passage connects the lubricant reservoir with the bearing area to channel lubricant from the lubricant reservoir to the bearing area. A second passage extends from the bearing area to the lubricant reservoir to allow lubricant to be channeled back to the lubricant reservoir. A groove system in the thrust flange of the cone cutter operates as a viscous or ram pump when rotating against the thrust flange of the bearing pin thereby providing a pumping action to circulate lubricant from the lubricant reservoir through said first passage to the bearing area and from the bearing area through said second passage back to said lubricant reservoir.