Pillow blocks can refer to a variety of bearing styles such as single row ball bearings, double row ball bearings, spherical roller bearings, taper roller bearings, etc. A unit is typically a reference for a 1-piece housing as opposed to a split housing. For simplicity, this article will focus on single row ball bearing units.
A basic pillow block bearing unit is typically an insert bearing which is based on a sealed deep groove ball bearing and a one piece housing.” Joshua Goldman, Applications Engineer for SKF USA says.
Pillow block bearing units are designed for quick, easy and safe mounting. They are sealed and pre-greased at the factory making them ready-to-use. Multiple sealing solutions and greases (including food grade greases) are available for specific application requirements. Some variants may be virtually maintenance-free depending on the application operating conditions. Because of the sphered outer ring interface, they can accommodate moderate initial misalignment, but normally do not permit axial displacement. These units offer a simple, cost-effective solution that can provide a number of benefits.