Abstract: A bolt anchor construction for attaching metal plates to the roof of a mine tunnel. An expansion shell having a plurality of spaced metal fingers extending from a collar is telescopically mounted on a bolt. A camming plug is threadably mounted on one end of the bolt and is located within and engageable with the spaced fingers. A series of coined teeth is formed in the outer surface of each finger. The camming plug is mounted within the spaced finger ends by a generally U-shaped bail and is movably retained therein to compensate for various size holes. The ends of the bail are secured to the collar. The camming plug forces the fingers outwardly upon rotation of the bolt whereupon the teeth bite into the rock surrounding the drilled hole to attach the plates to the mine roof. Vertical movement of the fingers with respect to each other is prevented by closing the shell collar by the overlapping of tabs formed on the collar ends.The fingers and collar are stamped from flat sheet metal in a progressive die.

Abstract: A bolt anchor construction for attaching metal plates to the roof of a mine tunnel. An expansion shell having a plurality of spaced metal fingers is telescopically mounted on a bolt. A camming plug is threadably mounted on one end of the bolt and is located within and engaged with the spaced fingers. A series of coined teeth is formed in the outer surface of each finger with the rear of the teeth forming a smooth, flat, tapered surface extending downwardly outwardly with respect to the inner surface of the fingers. The camming plug forces the fingers outwardly upon rotation of the bolt whereupon the teeth bite into the rock surrounding the drilled hole to attach the plates to the mine roof. A pair of spaced longitudinally extending bearing strips is formed on the inner surface of each finger for engagement with the camming plug, and the teeth smooth rear surfaces are located between the bearing strips and are free of projections to prevent bending with the plug.