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.

A deep groove in a ball bearing refers to the specific design feature of the bearing's inner and outer raceways, which allows it to accommodate radial and axial loads while enabling smooth and efficient rotation. The deep groove is a critical aspect of the ball bearing's construction and contributes to its performance in various applications.