... secondary enveloping surface.StructureIt is composed of main motor, gear reducer, double helical spur gear, universally-jointed axle, support, working seat, power ... screw down gear, left and right draw-works, hydraulic station and DC ... carbon steelSpeed of screw Dow gear0.058mm/sGear reducerZLYWorm gear for screw downA=315Double helical spur gearA:690; Mn ...