Abstract: A screw fastening apparatus for fastening a screw member having a bearing surface with respect to a member to be fastened by rotating the screw member from a theoretical seating point to a target rotational angle, including a rotational angle sensor which senses rotational angle values of the screw member for fastening the screw member, a torque detector which detects torque values for fastening the screw member, a torque value difference detector which detects a plurality of torque value differences, each of the torque value differences is a difference of the torque values detected at intervals of a constant rotational angle, a slip detector which detects a slip of the screw member with respect to the member to be fastened, from an average of the torque value differences, and a screw fastening discontinuing unit which instructs to discontinue the screw fastening when the slip is detected by the slip detector.

Abstract: A screw fastening apparatus for fastening a screw member having a bearing surface with respect to a member to be fastened by rotating the screw member from a theoretical seating point to a target rotational angle, including a rotational angle sensor which senses rotational angle values of the screw member for fastening the screw member, a torque detector which detects torque values for fastening the screw member, a torque value difference detector which detects a plurality of torque value differences, each of the torque value differences is a difference of the torque values detected at intervals of a constant rotational angle, a slip detector which detects a slip of the screw member with respect to the member to be fastened, from an average of the torque value differences, and a screw fastening discontinuing unit which instructs to discontinue the screw fastening when the slip is detected by the slip detector.