Pillow block bearings are mounted units that provide low friction support for shafts moving parallel to the mounting surface and passing through the unit’s center. Also called a plumber’s block, these bearings allow the shaft to smoothly glide in and out of the casing with little friction, resistance or heat. They are basically a ball bearing inserted into a mountable enclosure.
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The casings of pillow block bearings are usually made from cast iron, plastic, stainless steel or pressed steel to ensure the necessary strength and heat conduction properties while the bearing itself is typically constructed of smooth self-lubricating steel. The housing of the bearing is either one or two pieces, called unsplit or split, depending on whether or not the cap and base can be separately detached. Pillow block bearings are available in a variety of sizes, depending on the diameter of the hole, or bore, and they range from a few millimeters to approximately five centimeters in size. Various seals are provided to prevent dust and other contaminants from entering the housing so that it can provide a clean environment for ball bearings to freely rotate, which increases their performance and load capabilities. Pillow block bearings are used extensively in conveyor systems for the automotive and manufacturing industries as well as on automatic or robotic assembly lines, for die cutting tools, molds, punches and more.
Pillow block bearings can be mounted vertically on the wall or horizontally on the ceiling or floor. Some bearings are thicker and wider than others in anticipation of their applications. Though not motorized, pillow block bearings must be able to support heavy load capacities and the size of the bore and the diameter of the shaft should be carefully matched to ensure the smoothest and most secure fit. If the shaft is too wide, the increased surface area contact will cause more friction and the bearing will require heavy lubrication. Should the shaft be much smaller in diameter than the hole in the bearing, it will not slide through evenly and will add tension on the bearing and casing, causing wear and fatigue. Some styles enable both linear and rotary motion. For pillow block bearings that allow a rotating shaft to pass through, the bearing contains spherical rolling elements that rotate and travel in tracks, called races. The races are often oval in shape and the balls are exposed through the surface of the bearing to facilitate free motion of the shaft with low friction. For these bearings, a shaft can move in a straight line while also rotating on its radial axis. Depending on the application, the cylindrical holes in pillow block bearings can be completely closed or partially open to accommodate a shaft with an attached carriage or load.
