ON THE TIGHTENING OF BOLTS

For providing adequate tightening force for a bolted joint, the coeflicient of friction on the screw thread between bolt and nut and that on the seat between nut and pieces to be fastened together must be determined. The object of the present study is to analyze the static behaviour a bolted joint throughout the process ranging from tightening to loosening The authors separated the friction torque on the screw thread from that on the seat of nut to find successfully the values of the coeMcient of friction on the screw thread and on the seat of nut. It has been found that tightening torque for obtaining adequate tightening force can be determined with an error ranging between 20% by the proper selection of a lubricant.