Abstract: An anchor for a mine roof bolt incorporates a single large rib at the top of a segmented shell. This single large rib is forced into the wall of the bore hole by the downward movement of an associated threaded camming nut during the first few revolutions of the roof bolt. The remainder of the outer surface is generally smooth or unserrated and provides a large bearing surface which is urged against the bore hole wall upon further rotation of the bolt. The camming nut has a specific shape flaring substantially near its upper end such that a relative large area of the bore hole wall below the rib is forced into compression. When fully engaged, the camming nut compresses a tightening washer of a metal alloy softer that the camming nut or the shell. The washer is forced into the threads of the nut thereby preventing loosening of the bolt.

Abstract: An anchor for a mine roof bolt incorporates a single large rib at the top of a segmented shell. This single large rib is forced into the wall of the bore hole by the downward movement of an associated threaded camming nut during the first few revolutions of the roof bolt. The remainder of the outer surface is generally smooth or unserrated and provides a large bearing surface which is urged against the bore hole wall upon further rotation of the bolt. The camming nut has a specific shape flaring substantially near its upper end such that a relative large area of the bore hole wall below the rib is forced into compression.