Abstract: An earth-boring bit for attachment to a drill string has rotatable cones with rows of cutting elements. The cutting elements are arranged in generally circumferential rows on each of the cones and interference fit into apertures in the shell surface. The rows include a heel row of cutting elements on the heel surface of each of the cones, and an adjacent row of adjacent row cutting elements next to the heel row cutting elements. Each heel row cutting element has at least one counterpart adjacent row cutting element that is spaced no farther from it than any other adjacent row cutting element, defining a proximal pair. Each of the cutting elements in each of the proximal pairs has a grip ratio, which is the barrel length divided by the diameter. Some of the proximal pairs having cutting elements with higher grip ratios than other cutting elements. None of the proximal pairs has both cutting elements with higher grip ratios.

Abstract: Disclosed herein is a drill bit for earth boring that achieves pressure compensation or equalization of pressure across the seal separating the lubricant inside the bit from the drilling mud on the exterior of the bit by providing sufficient displacement of the seal to accommodate changes in lubricant volume caused by temperature and pressure changes encountered in drilling. By minimizing the volume of lubricant in the system, seal displacement may be minimized to produce pressure equalization across the seal without need for additional pressure equalization. Therefore, the lubrication system may be simplified and its reliability increased.