What prevents a bearing from seating on a shaft against the shoulder?

The best answer highlights how burrs on the shoulder can create a physical obstruction that prevents a bearing from properly seating against the shoulder of a shaft. Burrs are small, raised areas of metal that form due to improper machining processes or handling and can impede the uniform contact required for proper bearing installation. When a bearing is mounted on a shaft, it needs to fit snugly against the shoulder to ensure correct alignment and function, which burrs can disrupt, leading to potential issues such as misalignment or increased wear.

This issue is critical because if a bearing does not seat correctly, it may lead to operational problems such as vibrations, increased friction, or premature bearing failure due to improper loading. Ensuring that the shoulder is free of burrs and properly finished is essential for maintaining the integrity and functionality of the bearing and the system as a whole.