● A pillow block usually refers to a housing with an included anti-friction bearing. A pillow block refers to any mounted bearing wherein the mounted shaft is in a parallel plane to the mounting surface, and perpendicular to the center line of the mounting holes, as contrasted with various types of flange blocks or flange units. A pillow block may contain a bearing with one of several types of rolling elements, including ball, cylindrical roller, spherical roller, tapered roller, or metallic or synthetic bushing. The type of rolling element defines the type of pillow block. These differ from "plummer blocks" which are bearing housings supplied without any bearings and are usually meant for higher load ratings and a separately installed bearing.
● The fundamental application of both types is the same, which is to mount a bearing safely enabling its 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 may be either split type or solid type. Split type housings are usually two-piece housings where the cap and base may be detached, while others may be single-piece housings. Various sealing arrangements may be provided to prevent dust and other contaminants from entering the housing. Thus the housing provides a clean environment for the environmentally sensitive bearing to rotate free from contaminants while also retaining lubrication, either oil or grease, hence increasing its 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, including ductile iron, steel, stainless steel, and various types of thermoplastics and polyethylene-based plastics.
● The followings are brief introduction for several different types of pillow blocks.
● PILLOW BLOCKS---- UCP, UCPX, HCP, UCPK, HCPK, SAP, SBP
The most extensively used bearing units. UCP, UCPK and SBP are fixed to the shafts with set screws in the inner ring. HCP and SAP are fixed to the shafts with eccentric
locking collars. UPCK and HCPK are low base.
● HIGH CENTER HEIGHT PILLOW BLOCKS---- UCPH, HCPH
Pillow blocks with higher center heights.
● TAPPED BASE PILLOW BLOCKS---- UCPA, HCPA
Compact pillow blocks for limited space applications. Mounting is done with threaded bolts into the base.
● FOUR-BOLT SQUARE FLANGE UNITS---- UCF, UCFX, HCF, SAF, SBF
Units bolted to the sides of equipment with four bolts. Set screws and eccentric locking collars have the same mounting methods as housings with the “P” suffix.
● ROUND FLANGE UNITS---- UCFC, HCFC
Four-bolt units installed where concentricity is required.
● TWO-BOLT FLANGE UNITS---- UCFL, UCFLX, HCFL, SBFL
Housing saves space and weight and is installed with two bolts.
● TWO AND THREE-BOLT FLANGE UNITS---- SALF, SBLF
LF-type two-bolt flange units are used with SA and SB inserts only. SAFCT, SBFCT (ductile iron), SALFTC, SBLFTC (cast iron). Three-bolt flange units are used with SA and SB inserts only.
● FLANGE BRACKET UNITS---- UCFB
This mounting has three set holes on only one side of the flange. Used where mounting space is limited and the housing can be fixed on one side only.
● ADJUSTABLE FLANGE UNITS---- UCFA
Unit has a two-bolt base with one adjustable side, enabling the distance from the center of the shaft to be varied.
● TAKE UP UNITS---- UCT, HCT, UCST, UCSTX
Used where the center of the main shaft requires free alignment.
● PRESSED HOUSING PILLOW BLOCKS---- SAPP, SBPP
Lightweight unit consisting of two pressed steel plates. Used in equipment where the rotating speed is low or the machine has a light load. Inserts for pressed housings are
usually SA or SB series.
● PRESSED HOUSING ROUND FLANGE UNITS---- SAPF, SBPF
Lightweight housing consisting of two pressed steel plates mounted with SA or SB inserts.
● PRESSED HOUSING FLANGE UNITS---- SAPFT, SBPFT
Has the same function as pressed round flange housings. Used where mounting space is limited.
● PRESSED HOUSING OVAL FLANGE UNITS---- SAPFL, SBPFL
Compact unit has only two bolt holes and requires smaller mounting space. Function
is the same as other pressed flange housings.