Abstract: A bolt is fastened up to a predetermined snug torque Ts and then the bolt is further fastened by a specified angle ?t from a bolt angle corresponding to the snug torque Ts. Herein, in order to obtain excess and deficiency of the fastening angle up to the snug torque Ts, an angle-variation difference between the fastening angle ?sb of the bolt at the point where the fastening torque of the bolt has reached the snug torque Ts and a standard angle ?sa of the snug torque Ts is calculated. And, addition of this angle-variation difference to a base angle is set as the new specified angle ?t to correct the excess and deficiency. Accordingly, variation in a fastening shaft force can be restrained even if the snug torque is set at a relatively high torque in the bolt fastening method using the torque+angle method.

Abstract: A bearing cap, a type of thread-clamped member, is clamped to a cylinder block by flanged hexagonal bolts. The material of the bearing cap is aluminum alloy, while the material of the bolts is steel. The bearing cap has a raised seat the end surface of which provides a bearing surface. The bearing surface of the raised seat has a smaller diameter than the bearing surface of each bolt.

Abstract: A bolt is fastened up to a predetermined snug torque Ts and then the bolt is further fastened by a specified angle ?t from a bolt angle corresponding to the snug torque Ts. Herein, in order to obtain excess and deficiency of the fastening angle up to the snug torque Ts, an angle-variation difference between the fastening angle ?sb of the bolt at the point where the fastening torque of the bolt has reached the snug torque Ts and a standard angle ?sa of the snug torque Ts is calculated. And, addition of this angle-variation difference to a base angle is set as the new specified angle ?t to correct the excess and deficiency. Accordingly, variation in a fastening shaft force can be restrained even if the snug torque is set at a relatively high torque in the bolt fastening method using the torque+angle method.

Abstract: A bolt is fastened up to a predetermined snug torque Ts and then the bolt is further fastened by a specified angle ?t from a bolt angle corresponding to the snug torque Ts. Herein, in order to obtain excess and deficiency of the fastening angle up to the snug torque Ts, an angle-variation difference between the fastening angle ?sb of the bolt at the point where the fastening torque of the bolt has reached the snug torque Ts and a standard angle ?sa of the snug torque Ts is calculated. And, addition of this angle-variation difference to a base angle is set as the new specified angle ?t to correct the excess and deficiency. Accordingly, variation in a fastening shaft force can be restrained even if the snug torque is set at a relatively high torque in the bolt fastening method using the torque+angle method.

Abstract: An elasticity limit (limit of yieldingness resistance) of a fastened member (bolt's seat face) increases (an elasticity area expands) due to a plastic deformation of the fastened member by fastening a bolt in an initial fastening step, and the plastic deformation (yieldingness) of the fastened member is properly prevented from progressing even if a thermal stress acts after a final fastening step. Thus, decrease of a fastening shaft force of the bolt can be prevented properly despite removal of the thermal stress.

Abstract: After it is tightened with a snug torque TA, a bolt is tuned by a total turning angle ?S equivalent to the sum of an initial-set turning angle ?A and a corrective additional-turning angle (?B+?C). The corrective additional-turning angle (?B+?C) is the sum of a first corrective additional-turning angle ?B and a second corrective additional-turning angle ?C, the first corrective additional-turning angle ?B being to compensate for a situation where a bolt turning angle ?22 corresponding to the snug torque ?A on an extension line of the bolt tightening torque properties C2 in a late tightening stage II is different from a bolt turning angle ?11 corresponding to the actual snug torque TA, the second corrective additional-turning angle ?C being to compensate for a decrease of an effective bolt axial force that is caused by an existence of the initial tightening stage I.

Abstract: A bearing cap, a type of thread-clamped member, is clamped to a cylinder block by flanged hexagonal bolts. The material of the bearing cap is aluminium alloy, while the material of the bolts is steel. The bearing cap has a raised seat the end surface of which provides a bearing surface. The bearing surface of the raised seat has a smaller diameter than the bearing surface of each bolt.

Abstract: After it is tightened with a snug torque TA, a bolt is tuned by a total turning angle ?S equivalent to the sum of an initial-set turning angle ?A and a corrective additional-turning angle (?B+?C). The corrective additional-turning angle (?B+?C) is the sum of a first corrective additional-turning angle ?B and a second corrective additional-turning angle ?C, the first corrective additional-turning angle ?B being to compensate for a situation where a bolt turning angle ?22 corresponding to the snug torque ?A on an extension line of the bolt tightening torque properties C2 in a late tightening stage II is different from a bolt turning angle ?11 corresponding to the actual snug torque TA, the second corrective additional-turning angle ?C being to compensate for a decrease of an effective bolt axial force that is caused by an existence of the initial tightening stage I.

Abstract: According to a bolt tightening method and a bolt tightening apparatus of the invention, a bolt is tightened by using a bolt tightening device, in which torque gradients expressed in terms of the ratio of a tightening torque exerted on the bolt to its turning angle are calculated by successively detecting the tightening torque at intervals of a specific bolt turning angle and calculating an average of individual torque gradient values by first and second torque gradient calculators, and the amount of tightening of the bolt is controlled by a tightening amount controller based on the average of the individual torque gradient values calculated.

Abstract: According to a bolt tightening method and a bolt tightening apparatus of the invention, a bolt is tightened by using a bolt tightening device, in which torque gradients expressed in terms of the ratio of a tightening torque exerted on the bolt to its turning angle are calculated by successively detecting the tightening torque at intervals of a specific bolt turning angle and calculating an average of individual torque gradient values by first and second torque gradient calculators, and the amount of tightening of the bolt is controlled by a tightening amount controller based on the average of the individual torque gradient values calculated.

Abstract: A surface defect inspection apparatus includes a light radiation source, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward the surface to be inspected, a camera mechanism for receiving an image of the light radiation source, reflected by the surface to be inspected and forming a received-light image corresponding to the change pattern of the light radiation source, and a discriminator for discriminating a surface defect portion on the surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by the camera mechanism.

Abstract: In a method of tightening a screw member, the difference between the tightening axial force which is produced at the limit of elasticity when the friction coefficient between the screw member and a member into which the screw member is to be threaded is at a maximum and that when the friction coefficient between the screw member and the member into which the screw member is to be threaded is at a minimum is calculated, a seating torque is determined on the basis of the difference between the tightening axial forces, the screw member is threaded into the member into which the screw member is to be threaded until the tightening torque reaches the seating torque, and then the screw member is tightened by a predetermined angle.