Mounted bearings—also known as mounted units, bearing housings, or pillow block bearings—are essential components across modern industrial machinery. They provide stable support for rotating shafts, simplify installation, and reduce maintenance requirements. Whether used in conveyors, agricultural equipment, packaging lines, or heavy-duty processing machines, mounted bearings are engineered to deliver reliability and long operating life.
This comprehensive guide explains what a mounted bearing is, the four components that make up a mounted bearing unit, the types available, common applications, a practical mounted bearing size chart, and selection tips to help engineers, buyers, and maintenance teams choose the right option.
What Is a Mounted Bearing?
A mounted bearing is a ready-to-install assembly that consists of:
A rolling bearing insert (ball or roller bearing)
A housing (pillow block, flange, take-up, or other style)
Unlike standalone bearings, mounted bearings are pre-fitted into housings that allow easy bolting to machine frames. The insert bearing is typically spherical on the outside, allowing self-alignment, which compensates for minor shaft misalignment during installation and operation.
Why mounted bearings are widely used:
Easy and fast installation
Reduced alignment complexity
Pre-lubricated and often re-lubricatable
Improved contamination protection
Wide range of designs for different shaft sizes and environments
Mounted bearings are particularly valuable in industries where machinery operates continuously and downtime must be minimized.
The Four Main Components of a Mounted Bearing
Every mounted bearing unit, regardless of design, consists of four fundamental parts:
1. Bearing Insert
The bearing insert is the actual rolling bearing that supports the shaft.
Common insert types include:
UC Series: Set-screw locking insert bearings
UK / NA Series: Adapter sleeve locking types
UE / SA Series: Eccentric locking collar types
The insert usually features:
Wide inner ring for strong shaft clamping
Spherical outer surface to allow self-alignment
Built-in seals to block dust, moisture, and contaminants
2. Bearing Housing
The housing encases and supports the insert bearing.
Common housing materials include:
Cast iron
Ductile iron
Stainless steel
Thermoplastic (ideal for food and washdown environments)
Housing designs vary depending on mounting requirements:
Base-mount (pillow block)
Side-mount (flange units)
Slotted designs for tensioning (take-up units)
3. Shaft Locking Mechanism
The locking mechanism secures the inner ring of the bearing to the shaft, preventing slipping.
Common locking styles:
Set screw locking (most common)
Eccentric locking collar (smooth locking for low-speed machines)
Adapter sleeve / tapered bore (strong grip for heavy load applications)
Choosing the right locking method is essential for maintaining shaft integrity and long-term performance.
4. Seals and Lubrication System
Seals protect the bearing from contamination and retain lubrication.
Common seal types:
Single-lip seals
Double-lip seals
Labyrinth seals (excellent for harsh environments)
Lubrication options:
Factory pre-lubricated (sealed-for-life)
Grease fittings for re-lubrication
Together, these four components determine the bearing’s performance, load capacity, speed rating, and durability.
Types of Mounted Bearings
Mounted bearings can be categorized by housing style, bearing insert type, and locking method. Understanding the differences helps you select the best unit for your application.
1. By Housing Style
Pillow Block Bearings (UCP Series)
The most common mounted bearing type.
Features:
Base-mounted
Two or more bolt holes
Easy alignment
Suitable for conveyors, fans, and general machinery
2-Bolt Flange Bearings (UCF / UCFL Series)
Installed on the side of equipment or walls.
Compact design
Excellent for tight spaces
Widely used in agricultural equipment and material conveyors
4-Bolt Flange Bearings (UCFC / UCFB / UCFX Series)
Heavy-duty mounting with four bolts for maximum stability.
Good for high-load or high-vibration applications
Supports large shaft diameters
Take-Up Units (UCT Series)
Mounted in slotted frames to adjust shaft or belt tension.
Common in conveyor systems
Allows sliding adjustment forward/back
Plummer Block / Spherical Roller Housings
Heavy-duty housings for large bearings.
Compatible with spherical roller bearings
Capable of handling high radial loads
Used in mining, steel mills, crushers, and high-shock applications
2. By Bearing Insert Type
Ball Bearing Inserts
Most common
Support moderate radial loads
Available with multiple locking options
Ideal for general machinery
Spherical Roller Inserts
High radial load capacity
Excellent for misalignment
Used in heavy-duty, harsh-environment equipment
Tapered Roller Inserts
Support combined radial and axial loads
Used in demanding mechanical drives
Plain / Sleeve Bearings
Used for low-speed, high-load applications
No rolling elements
Long operating life with proper lubrication
3. By Shaft Locking Method
Set Screw Locking
Simple and cost-effective
Perfect for low-to-medium loads
Most commonly used in UC-type bearings
Eccentric Locking Collar
Smooth and reliable shaft attachment
Suitable for low-speed applications such as agricultural machinery
Adapter Sleeve Locking
Best performance for heavy loads
Provides concentric and secure shaft grip
Common in plummer block housings
What Are Mounted Bearings Used For?
Mounted bearings are used anywhere a rotating shaft needs to be supported and aligned. Their design makes installation easy and maintenance minimal.
Typical applications include:
1. Material Handling
Belt conveyors
Roller conveyors
Palletizing equipment
2. Agriculture
Harvesters
Grain augers
Feed systems
3. Food Processing
Washdown equipment
Packaging conveyors
Mixing machines
4. HVAC and Fans
Air handling units
Industrial blowers
Ventilation systems
5. Mining and Construction
Crushers
Vibrating screens
Heavy-duty conveyors
6. General Industrial Machinery
Pumps
Gear reducers
Textile machines
Automation systems
Because mounted bearings come pre-assembled, they’re ideal for equipment where downtime must be minimized.
Mounted Bearing Size Chart (UC Insert Example)
The following table lists common UC-series insert bearings used in pillow blocks, flange units, and take-up housings.
| Insert Model | Bore (mm) | Outer Diameter (mm) | Width (mm) |
| UC201 | 12 | 47 | 16 |
| UC202 | 15 | 47 | 16 |
| UC203 | 17 | 47 | 16 |
| UC204 | 20 | 47 | 16 |
| UC205 | 25 | 52 | 17 |
| UC206 | 30 | 62 | 19 |
| UC207 | 35 | 72 | 20 |
| UC208 | 40 | 80 | 21 |
| UC209 | 45 | 85 | 22 |
| UC210 | 50 | 90 | 23 |
| UC211 | 55 | 100 | 24 |
| UC212 | 60 | 110 | 26 |
| UC213 | 65 | 120 | 28 |
| UC214 | 70 | 125 | 29 |
This chart helps engineers quickly determine the correct bearing insert for matching housings such as UCP, UCF, UCFL, UCT, etc.
How to Select the Right Mounted Bearing (Practical Checklist)
Choosing the correct mounted bearing requires understanding the application’s loads, environment, and maintenance requirements.
1. Load Requirements
Ball inserts: moderate radial loads
Spherical roller inserts: heavy shock loads
Tapered inserts: high combined radial + axial loads
Always compare application loads with catalog dynamic/static load ratings.
2. Shaft Size and Locking Style
Set screws: most economical
Eccentric collars: low-speed agricultural machinery
Adapter sleeves: heavy machinery and large shafts
Correct shaft fit prevents slippage and misalignment.
3. Speed Requirements
Check limiting speed for each insert type
Ensure lubrication type matches operating speed
High-speed applications require low-friction seals
4. Misalignment Capabilities
UC inserts allow self-alignment
Spherical roller units offer the highest misalignment tolerance
Misalignment compensation helps prevent premature bearing wear.
5. Operating Environment
Wet/chemical: stainless steel units
Washdown: thermoplastic housings + food-grade grease
Dusty/mining: heavy-duty seals + re-lube capability
6. Maintenance Strategy
Choose sealed units for low maintenance
Choose re-greasable units for harsh environments
7. Interchangeability and Mounting Dimensions
Confirm bolt hole distances
Verify shaft height and flange dimensions
Check replacement units match existing housings
Common Installation Mistakes to Avoid
Over-greasing or under-greasing
Using the wrong locking method for the shaft
Installing housings on uneven mounting surfaces
Ignoring alignment between multiple bearing units
Mixing inserts and housings from incompatible series
Proper installation directly affects operating life.
Conclusion
Mounted bearings are an essential solution for supporting rotating shafts across all industries. Their simplified installation, built-in alignment capabilities, and versatile housing styles make them ideal for conveyors, agricultural machinery, HVAC systems, packaging equipment, and heavy-duty industrial machines.
By understanding the four key components—bearing insert, housing, locking method, and sealing system—along with application requirements such as load, speed, environment, and maintenance strategy, users can confidently choose the right mounted bearing for any application.
BYWB Bearing provides high-quality mounted bearings designed for durability, long service life, and smooth performance. Whether you need pillow block units, flanged bearings, take-up housings, or spherical roller units, BYWB offers reliable solutions for OEMs, distributors, and end users worldwide.
