What is a Bearing Unit? Know Features, Types and Materials Available
Publish Date: 6 Oct 2025
A bearing unit is precisely engineered to provide reliable shaft support and smooth rotation in equipment ranging from conveyors to factory machinery. It consists of a ball bearing, sealing system, and a firmly mounted housing—usually cast iron, steel plate, stainless steel, zinc alloy, or resin depending on the specific application. Key structural features include a deep-groove, double-sealed bearing that absorbs both radial and axial loads, honed raceways for reduced friction, and a precisely machined housing designed to avoid stress concentration and maximize breaking strength.
Technical Features
Bearing units commonly offer a self-aligning mechanism made possible by a spherical outer ring on the bearing insert that fits into a concave housing bore. This allows for automatic adjustment to minor shaft misalignments, improving operational life and reducing excess bearing loads. Standard units allow for up to 3° alignment accommodation; units with solid or covered housings allow up to 1°. Many products feature special seals, dust flingers, oil inlet angles for easier lubrication, and set screws or collars that provide secure fastening while preventing inner ring deformation from overtightening.
Bearing Unit Housing Types
| Type | Description | Typical Use |
|---|---|---|
| Pillow Block | Horizontal base, easy installation | Conveyor, shafts |
| Square Flanged | Four-bolt mount for strong fixation | Machine frames, panels |
| Round Flanged | Circular design, compact mounting | Small devices, low loads |
| Diamond Shape Flanged | Diagonal two-bolt, saves installation space | Tight space installations |
| Take-Up | Adjustable, corrects misalignment | Belt tensioning systems |
| Deformed Diamond-Shaped | Modified flange for custom formats | Special machinery |
Bearing Unit Body Materials
| Material | Key Features | Usage Scenario |
|---|---|---|
| Cast Iron | High strength, standard, good vibration absorption | General, heavy-duty applications |
| Stainless Steel | Corrosion resistance, easy to clean | Food, medical, corrosive areas |
| Steel Plate | Cost-effective, lighter than cast iron | Basic environments, moderate load |
| Structural Steel | Excellent strength, general-purpose | Machine frames, industrial setups |
| Zinc Alloy Die-Cast | Lightweight, rust resistance | Light-duty, compact machinery |
| Resin | Chemical resistance, lightweight, quiet operation | Clean, chemical, low-load areas |
Type of Pillow Block and it's Comparison
| Variation | Housing Construction | Bearing Type Options | Key Features | Typical Applications |
|---|---|---|---|---|
| Standard | Solid cast iron | Ball, spherical, plain | Versatile, rigid, easy mounting | General machinery, conveyors |
| Thick | Extra-thick cast iron | Ball, spherical, plain | Higher rigidity, shock resistance | Heavy-duty, cranes, impact areas |
| High Center | Raised cast iron | Ball, spherical | Shaft mounted higher than base for specific alignment | Roller conveyors, printing machines |
| Narrow Width | Cast iron, compact | Ball, spherical | Slim footprint, threaded mounting hole | Tight spaces, narrow roller pitch |
| Lightweight | Thin cast iron/steel | Ball, plain, tight fit | Reduced weight, compact, absorbs vibration | Small equipment, light duty, packaging |
Bearing units are essential components that ensure smooth, stable, and efficient shaft rotation in various machines. With different shapes, materials, and mounting styles available, MISUMI’s wide range of bearing units provides reliable performance for every application — from general industrial use to specialized environments. Whether you need durability, corrosion resistance, or compact design, MISUMI offers the right bearing unit to meet your needs with precision and quality.
