Angle control tightening of engine bolts

In order to meet the demand for motor cars with reduced cost and weight, the bolts must be tightened more precisely and stably. Tightening techniques – the plastic region tightening method and the elastic region angle–controlled method, instead of the conventional toraue–controlled method – were studied and successfully applied to main engine parts. In addition to angle control with snug torque, seating point control was also developed, and both methods were applied to the plastic region tightening method. These methods were applied to elastic region angle control and resulted to high tightening quality in such ways as an improvement in separation load of connecting rod mating face and obtaining a proper clearance between the crankshaft journal and the metal.