Abstract: The specification discloses an insert tipped tool bit having grooves formed on the longitudinal periphery of the bit in the parent material supporting the insert and a method of reducing erosion of the insert supporting parent material by forming grooves on the longitudinal periphery of the tool bit and sizing and spacing the grooves so that earth fines can pack in the grooves and create a boundary layer of earth fines around the parent material.

Abstract: A tool for being inserted in a hole, especially a hole in an earth formation, and adapted for being rotated in the hole. A cutting element moveably mounted on the tool is provided for cutting a groove in the hole and, if the tool is moved axially in the hole while rotating, a helical groove will result. The cutting element is retractable to permit removal of the tool from the hole. The hole with the groove formed therein is adapted for receiving a roof bolt or the like which is cemented in place and the aforementioned groove improves the strength with which the bolt is held in the hole.