A cross bar of a planer weighing 9 kN is raised and lowered bymeans of two square threaded screws
of 40 mm outside diameter and 6 mm pitch. The screw is made ofsteel and nut of phosphor bronze
having 42 mm height. A steel collar bearing with 30 mm mean radiustakes the axial thrust. The
coefficient of friction at the threads and at the collar may beassumed as 0.14 and 0.10 respectively.
Find the force required at a radius of 120 mm of a handwheel toraise and lower the load. Find also the
shear stress in the nut material and the bearing pressure on thethreads.
