Cam structure of electric, pneumatic screw driver

The utility model relates to an electric or pneumatic screwdriver technology field, in particular to a cam structure of an electrical or pneumatic screwdriver, a annular recess is opened on the cam and a torque jump-off plate, and the annular recess is fully filled with steel balls so that the cam and a drive shaft are combined, and the steel balls fastens the cam and the torque jump-off plate to fasten the relevant components, when in operation, excursion does not happen but operates stably, the cam portion of the cam is hanging in the torque jump-off plate, which makes a certain space always maintained between the cam portion of the cam and the torque jump-off plate, so the accurate and stable set torque values can be maintained long-actingly. The inclined surface at two sides of the cam portion have different grade of slope relative to the orbital plane, so the back acting output torque is greater, the screw can be withdrew one time when removing a screw without multiple operation or adjusting the torque force, the operation is more convenient and the working efficiency is increased.