Bearing Design Fundamentals

The Benefits of Using Ball Bushing Bearings in Linear Motion  

by Kevin Sweeney
23 June, 2023
7 min read

In 1945, linear ball bushings were patented, and they began to be marketed commercially during the 1950’s. Ball bushings were the primary linear motion guidance system until the 1970’s, when profiled linear rail guides were introduced. The choice exists for designers to use the more accurate and more precision linear rail guides or the more economical linear ball bushing. Linear ball bushings have improved over the years, increased load capacities and having the self-alignment feature has given designers a variety of qualified reasons to specify either type in their applications.

Ball bushings are a relatively inexpensive option to achieve linear motion in industrial machinery, robotics, and various mechanical systems. As engineers strive for economy and efficiency, ball bushings provide both. Linear ball bushings are designed to minimize friction and operate smoothly and accurately. They are also a good linear motion option providing precise control, self-alignment, long-lasting performance, and value. This article will consider the reasons for integrating ball bushing bearings into linear motion systems.

NB Ball Bushing open and flanged version

Reduced Friction and Enhanced Efficiency

Leading linear bearing manufacturers such as NB Bearing Company manufacture a full product line of linear bushings. Linear ball bushing bearings provide smooth linear motion using the rolling motion of recirculating balls in a channel as the inside raceway. See below the various NB types available. Many linear ball bushing manufacturers offer similar variety models such as those shown here.

Basic Structure of NB Linear Bushing Bearings (SM, SMF, GM)

GM type has the resin outer cylinder, SM type is steel outer, and SMF has steel outer and flange

Key Features At-A-Glance

Linear ball bushing bearings will have a round bore that provides for a space saving design allowing for smaller and lighter components. The shafts provided by Pacific International Bearing are precision ground, which minimizes contact with the ball elements which in turn reduces friction and results in a smoother linear movement. When a double lip seal is incorporated, grease leakage is reduced significantly.

THK linear ball bushing bearing manufactured from resin

Many manufacturers such as INA and NB produce linear ball bushings as standard or with anti-corrosion components. With the diverse options available, ball bushings can meet the demands for most applications. You can consider linear ball bushing bearings as an option for use in harsh environmental conditions. Linear ball bushing bearings manufactured from resin construction are good choices for low cost or less demanding applications.

Some manufacturers like INA and NB linear bearing company provide both linear ball bushing bearing and matching precision shafting. The NB FIT series is a combination of linear bushing bearing and precision-machined shaft. The best fit between linear bushing and shaft yields a high accuracy performance and smooth operation.

Why Use Resin Material for the Body of the Bushing? 

NB, THK, INA, and others use resin material in the manufacture of linear ball bushings where around 50% weight reduction is achieved over conventional steel versions. Even the ball return can be made of resin material, further reducing weight. Another benefit of using resin is the reduction in noise. You should consider the NB GM/GW resin type linear ball bushing bearing for its cost effectiveness and expanded application use. Contact Pacific International Bearing for more information.

  • High Load Capacity, Durability, and Cost Savings

Due to the design characteristics of linear ball bushings the user will experience reduced installation time and increased cost savings.

Linear ball bushing bearings provide higher load capacity, longer service life, and reduce material costs. The use of linear ball bushings will yield improvements in energy savings during operation.

  • Low Noise and Smooth Operation

As suggested, the use of resin material will enhance the smooth operation and contribute to reducing noise during operation. Bearing noise is reduced especially when the ball retainer is also manufactured from a resin material. Controlling internal play is achieved by specifying higher tolerance versions.

  • Design Flexibility and Self Aligning Feature

When considering using linear ball bushings over profiled rails one benefit is the self-aligning feature. Rail guides can provide greater stiffness and carry higher loads, but will bind if used in pairs and not properly aligned. Ball bushings will rotate on the shaft and compensate for any shaft misalignment. Use of ball bushings is also a good option when the mating components are lower precision.

Typical ball bushings are designed to accommodate a misalignment tolerance of ±0.5 degrees. In addition to making up for inaccuracies in mounting surfaces, alignment, or shaft deflection, self-aligning linear ball bushings provide an even distribution of the load across the entire length of the ball bushing. This feature will prevent pressure between the end edge of the bushing and the shaft, making for low friction and smooth-running characteristics.

  • Seals

Seals are an option available on ball bushings that are important in many applications where you may encounter the ingress of contaminants.

One consideration when the ball bushing is self-aligning or tilting the seal may lose contact with the shaft and become ineffective. Most manufacturers offer floating seals to overcome this issue and are used to maintain the constant pressure needed for effective sealing. Floating seals are also good for reducing friction found in conventional seals.

  • Applications

You can find NB, THK, INA, and all brands of linear bushing bearings in transportation equipment, food processing equipment, semiconductor manufacturing equipment, and industrial robotics as well as numerous industrial, commercial, and scientific systems that require smooth, precise motion.


Linear ball bushings, also known as ball bushing bearings, are mounted on a round shaft used for linear motion guidance. Linear ball bushings are self-aligning and operate with low friction. Because of this, they can be a more economic and efficient option for many linear motion applications.

Still have a question or need to discuss something? Contact us to get help.

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Written by

Kevin Sweeney

Founder and CEO at Pacific International Bearing Sales Inc (PIB)
Education: BS Business and Economics California State University Hayward Ca
CBS (Certified Bearing Specialist)

My role with Pacific International Bearings (PIB) is currently CEO. Since 1976, I have been deeply involved in the bearing industry, working in manufacturing sales at NTN Bearing and subsequently in Bearing Distribution. Before establishing PIB in 1990, I gathered valuable experience in bearing manufacturing and distribution. The last 45 + years in the bearing industry have been both rewarding and challenging, assisting customers across a large number of diverse bearing applications.
Outside of the bearing industry, my interests are family, woodworking, motorcycling, cars, gardening, and golf.
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