The document provides an overview of linear bearings and rail guides, detailing their historical context, anatomy, and options for mounting on square or round rails. It highlights the differences in load capacity, precision, and installation requirements of square versus round rails, and discusses caged versus non-caged linear bearings, including their performance benefits. Additionally, it explains the importance of preload for optimal bearing function and offers guidance on selecting preload amounts based on specific applications.

1. LINEAR BEARINGS
An Overview of Linear Bearings and Rail Guides
Trimantec.com

2. BALL BEARINGS WERE
FOUND IN THE REMAINS OF
THE ROMAN NEMI SHIPS IN
LAKE NEMI, ITALY, DATING
BACK TO 40 BC.
Mechanical Bearings in History
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3. LINEAR BEARING ANATOMY
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CARRIAGE
The housing for the bearing balls or rollers which is mounted onto the
linear guides (rails).
ROLLING
ELEMENT
The rolling element of the bearing, whether it be ball or roller slides, helps
move a load with ease.
RAIL/GUIDE
The mounting system for the linear bearing. Linear bearings can be
mounted on either square or round rail guides.

4. SQUARE RAILS
High load capacity
High precision accuracy
Stiff, rigid
Requires a truly flat
mounting surface and
parallelism
Rails need to have support
throughout the mounting
system.
Square rails and guides offer the benefits of a higher load capacity
and precision accuracy. However, to achieve these benefits they
require careful installation to ensure parallelism and a flat
mounting surface.

5. ROUND RAILS
More forgiving of
misalignment, and poor
parallelism
Installation is easier,
inexpensive
Can be end supported or
have intermittent supports
Smaller load capacity than
square rails
Round rails, on the other hand, are quicker to install and can
handle imperfect parallelism and greater changes in rail height.
The downside to round rails is their load capacity isn’t as high as
that of square rails.

6. CAGED VS NON-CAGED
A caged linear bearing includes a retainer for
the balls inside the bearing for even spacing.
Originally, linear bearings did not include a
cage structure and nowadays these are
referred to as non-caged linear bearings.
Higher performance speed
Longer bearing life span
Quieter, smoother operation
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Advantages to Caged Linear Bearings

7. WHAT IS PRELOAD?
Linear bearings need preload to function at their best. Preload
eliminates any internal clearance within the bearing. The bearing is
stiffer afterwards and ready to handle the load it will carry. Often
times linear bearings are sold already preloaded, so it’s a good idea
to check with the manufacturer.
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8. HOW MUCH PRELOAD?
While preload can do good for the linear bearing it can also diminish its life span.
That’s why it’s best to choose the amount of preload based on your specific application.
Below is a chart with recommended preload amounts based on different applications.
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Preload No Preload Light Preload Medium/Heavy Preload
Welding machine
Chopping machine
Feeding mechanism
Tool change
mechanism
Ordinary XY table
Packing machine
NC lathe
EDM
Precise XY table
Ordinary Z-axis
Industrial robot
PCB punching
machine
Machine tool
NC lathe and milling
machine
Feeding axis of grinder
Tool feeding axis
Applications

9. READ THE FULL BLOG
ON LINEAR BEARINGS
AND RAIL GUIDES:
WWW.TRIMANTEC.COM/BLOG