Tension gauge

Abstract

A tension gauge for indicating the tension on a fastener such as a mine roof bolt is a non-metallic right circular cylinder having a central bore and an axial thickness between parallel top and bottom surfaces. A plurality of radially extending holes is equally spaced around the perimeter of the cylinder, an end of each hole in communication with the bore and/or an end opening in the perimeter of said cylinder. Preferably, there are six such holes disposed at 60.degree. intervals about the cylinder bore. The central axis of each hole lies in a plane which is parallel to and substantially equidistant from the planes of the top and bottom surfaces. The cylinder is formed of a one-piece, compressible, organopolymeric material, such as high density polyethylene, which is capable of flowing under compression resulting from tension on the fastener less than that tension which will overstress the fastener. In use, the cylinder is positioned on a mine roof bolt between a roof plate having an annular rib and a washer adjacent the driving head of the bolt. As the bolt is tightened, the tension gauge is compressed to such an extent that the organopolymeric material flows radially and axially. The bolt is properly torqued when the material is compressed to the point where it can be visually observed that the dimples formed in the material have reached the level of the visible bottom surface of the washer and the material between the dimples extends only a short distance below the bottom surface. The gauge provides an indication of undertension, proper tension and over-tension.

Dependencies are inferred from the claim text.