A conventional power tool primarily includes a motor, a hammer drivingly rotated by the motor, and an anvil. The hammer collides with the anvil and imparts torque thereto. The torque provided to the anvil is transmitted to an end tool for tightening a screw or performing another fastening operation. In this type of power tool, the torque applied to the anvil and transmitted to the end tool is generated by the impact between an engaging protrusion provided on the hammer and an engagement protrusion provided on the anvil.