Crank bearing cap needed to secure strict metal clearance of the crankshaft by fixing bearing firmly at the time of high rotation and high load, enduring the force from bend or torsion vibration. However, in combination with a common bolt and nut, no matter what strengthen bolt it may used, bolting power concentrates on from third mountains to the 1st mountain of the screw, and the total bolting power cannot be increased beyond a certain value. Moreover, excessive stress is concentrated and may damage the bolt. Stud bolt, on the other hand, is applied dynamic design to its threading so that the bolting force is dispersed to all the screw threads and mighty bolting power is generated.
