Bolt with over-stress indicator - has markings on shank near head and near screw thread

摘要

The bolt (1) has a hexagonal head (2) at one end and a screw thread at the other end, with a plain part (4) of the shank between the screw thread and the head. The surface of the plain part is marked with two lines (5) parallel to the bolt axis. One of these lines is immediately under the bolt head whilst the other line adjoins the screw thread and the two lines are in line with each other. After the bolt has been used, the relative displacement of the lines to the positions (6, 6') indicates if the bolt has been torsionally stressed beyond its yield point. This feature can be visually observed without the need for elaborate measuring equipment. USE - Detection of overstressed bolts.