In summary, main bearings are primarily responsible for supporting the rotational motion of the crankshaft and withstanding radial loads, while thrust bearings are designed to counteract axial forces and maintain the axial position of the crankshaft. Both types of bearings play critical roles in ensuring the smooth and reliable operation of engines and machinery.

The term angle of contact in the context of ball bearings refers to the angle formed between the direction of the load and a line perpendicular to the bearing axis. In the case of angular contact ball bearings, this angle is specifically designed to optimize the bearing's ability to support combined radial and axial loads, as well as pure axial loads in a specific direction.