Cylinder-head bolts

When cylinder-head bolts in an automobile engine are tightened, the critical quantity is the torque applied to the bolts. Why is the torque more important than the actual force applied to the wrench handle?



Since torque is indirectly influencing the angle through which the bolt rotates, the greatest torque results in the tightest fit. Torque is governed but not just the applied force but also the distance from the axis of rotation (lever arm).



(Young, Hugh, and Roger Freeman. University Physics. 12th. San Francisco: Pearson Education, 2008.)