Pages 333-334
The compressive force method for bolt tightening can be improved by finding the bolt head which has a constant frictional coefficient from the start to the end of tightening. Variations of frictional coefficient between bearing surfaces have been investigated on various bolt head types with different conic angles of bearing surfaces and with configuration error such as burr on the edge of bearing surfaces. It has been found that the bolt head type with +1° to bolt head and to outside has almost constant frictional coefficient and is expected to be the optimum head geometry. Tightening experiments have shown that the optimum one has the most accurate clamping force by the compressive force method.
