By using an approach developed to determine the torque-tension relationship for bolted joints, frictional properties of several typical bolted joints were studied experimentally. The specific property by bolted joints certify that the most significant influence of materials and bearing surface condition. Experiments on thread friction shows that prevailing torque nuts with distorted threads provide benefit for preventing self-loosening of the nut. Repeated tightening-loosening generally increases frictions in a bolted joint. It was noted that the data scatter of the experimental results of frictions in a belted joint may overshadow the influence of size. speed, and contact positions. The results from the experimental investigation will help to better design bolted joints.