圈上大峰 Torque Loading-Load Lowering3 (Loosening screw) The torque for lowering the load is a product of the force P and the mean radius or d/2. 2πdnm+f This torque is responsible for overcoming thread friction and to lower the load. 53 圈上大峰 Effect of Thread Angle3 .For other threads(not square thread),the normal force acts at an angle. .Angle a increases frictional force by wedging action of the threads. .Can be accounted for by dividing frictional terms by cos a. Threa angle53 The torque for lowering the load is a product of the force P and the mean radius or dm / 2. This torque is responsible for overcoming thread friction and to lower the load. Torque Loading-Load Lowering3（Loosening Screw）           d fl Fd fd l T m m m   － 2 54 Effect of Thread Angle3 •For other threads( not square thread), the normal force acts at an angle. •Angle  increases frictional force by wedging action of the threads. •Can be accounted for by dividing frictional terms by cos . α