What Is a Pivot?
A pivot is a rotating shaft with a conical end, commonly used in machine building and machining. Pivots are typically paired with bearings to reduce friction in rotating components of machinery, particularly at high speeds. A key feature of pivots is their interaction with multiple spherical bearings, which results in lower friction due to rolling contact.
Uses of Pivots
Pivots find application in machinery that involves high-speed rotation. For instance, turbo molecular pumps in vacuum factories or academic research facilities use pivots for creating high vacuum environments (0.1~10-5 Pa). These pumps have blades rotating near the speed of sound. In computer hard disks (HDDs), pivots play a crucial role in reducing frictional losses as disks rotate at high speeds for data reading and writing.
Principle of Pivots
Pivots are integrated with pivot bearings to form a rotating assembly. These bearings consist of an outer ring and several spheres, with the pivot’s conical tip passing through the ring’s center and making contact with the spheres. This design allows for reduced friction during rotation.
Such bearings, supported by spheres, are known as ball bearings. The pivot’s tip is typically angled at 60° and finished with a small spherical surface. When used at high speeds, lubrication may be necessary. The size and capacity of the pivot bearing should be chosen based on the weight and other characteristics of the rotating components. An alternative to pivots is cylindrical bearings, or plain bearings, which have a larger contact area and thus higher frictional losses. However, they can be more efficient in power transmission through their contact surface.