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.

In summary, the angle of contact in angular contact ball bearings is a fundamental design feature that enables the bearing to support combined radial and axial loads, accommodate high-speed operation, and provide high precision and rigidity in various industrial applications.