A pillow block, also known as a plummer block or bearing housing, is a pedestal used to provide support for a rotating shaft with the help of compatible bearings & various accessories. Housing material for a pillow block is typically made of cast iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

or cast steel.

Selection

Pillow blocks are usually referred to the housings which have a bearing fitted into them & thus the user need not purchase the bearings separately. Pillow blocks are usually mounted in cleaner environments & generally are meant for lesser loads of general industry. These differ from "plummer blocks" which are bearing housings supplied without any bearings & are usually meant for higher load ratings & corrosive industrial environments. However the terms pillow-block & plummer-block are used interchangeably in certain parts of the world.

The fundamental application of both types is the same which is to primarily mount bearings safely enabling their outer ring to be stationary while allowing rotation of the inner ring. The housing is bolted to a foundation through the holes in the base. Bearing housings are either split type or unsplit type. Split type housings are usually two piece housings where the cap and base can be detached. While certain series are one single piece housings. Various seals are provided to prevent dust and other contaminants from entering the housing. Thus the housing provides a clean environment for the expensive bearings to freely rotate hence increasing their performance and duty cycle.

Bearing housings are usually made of grey cast iron. However various grades of metals can be used to manufacture the same.

ISO 113 specifies internationally accepted dimensions for plummer blocks.