How Linear Shafts Improve Motion System Performance

Linear Shafts: Types, Mounting Options and Materials

Linear shafts are precision ground rods that provide guidance and support for linear motion systems. They work with linear bearings to reduce friction, improve accuracy, and support loads in applications ranging from manufacturing equipment and packaging machinery to aerospace and medical devices.

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What are Linear Shafts?

A linear shaft is a cylindrical rod used with linear bearings to create smooth, controlled motion in a straight line. The shaft acts as the bearing's running surface and directly affects system accuracy, load capacity, and overall performance.

Linear shafts are long, rod-shaped devices that provide linear motion for different applications. Linear motion applications are found in the medical, aerospace, packaging and industrial sectors and more.

A better shaft equals better performance. The shaft design plays a crucial role as the shaft performs as the bearing system's inner ring or cone (inner race). The inner race is the part of the bearing that sits directly on the shaft.

Shafting is a critical component in linear motion machines. There are different types of linear motion shafts to get the job done.

Why Are Linear Shafts Important in Motion Systems?

Reduced friction
Improved accuracy
Bearing support
Increased equipment reliability
Longer component life

What Types of Linear Shafts Are Available?

Linear shafts are available in several configurations, each designed to solve specific mounting, weight, and performance challenges. Selecting the proper shaft design helps improve system reliability, simplify installation, and ensure the shaft can properly support the intended load.

What Is a Tapped Linear Shaft?

Tapped linear shafts contain internal threads machined into one or both ends of the shaft. These threaded holes allow the shaft to be secured using bolts or threaded studs, creating a clean and secure mounting arrangement.

Tapped shafts are often chosen when equipment designers want the shaft anchored without the need for external brackets or support structures. Because the fastening hardware is contained within the shaft, the overall assembly typically has a cleaner appearance and requires less installation space.

Common benefits of tapped shafts include:

Simplified installation
Secure end mounting
Reduced need for additional support hardware
Clean and compact system design

Typical applications include:

Packaging equipment
Automated assembly machinery
Medical devices
Laboratory automation systems

When properly installed, tapped shafts can provide excellent rigidity while maintaining precise linear motion performance.

What Is a Threaded Linear Shaft?

Threaded linear shafts feature external threads on one or both ends. Unlike tapped shafts that receive a fastener internally, threaded shafts are inserted directly into tapped mounting holes or secured with locking nuts.

Threaded shafts offer a versatile mounting solution and are commonly used when adjustability or easy replacement is required. The threaded ends allow installers to precisely position and secure the shaft during assembly.

Advantages of threaded shafts include:

Easy installation and removal
Adjustable positioning
Strong mounting capability
Reduced need for custom mounting hardware

Common applications include:

Conveyor systems
Material handling equipment
Robotics
Industrial automation machinery

Many engineers prefer threaded shafts when field serviceability is important because components can often be replaced without extensive machine disassembly.

What Is a Hollow Linear Shaft?

Hollow linear shafts feature a precision-machined bore running through the center of the shaft. Removing material from the center reduces weight while maintaining much of the shaft's structural integrity.

The lower mass of hollow shafts makes them particularly valuable in high-speed motion systems where reducing moving weight can improve acceleration, responsiveness, and overall efficiency.

In some applications, the hollow center can also be used to route cables, air lines, sensors, or other components through the shaft, helping create a more compact machine design.

Key advantages include:

Reduced system weight
Lower inertia during movement
Improved acceleration and deceleration
Potential routing space for wiring or tubing
Increased energy efficiency in moving systems

Common applications include:

Pick-and-place automation
Robotics
Aerospace equipment
High-speed manufacturing systems

While hollow shafts provide significant weight savings, engineers must still evaluate load requirements carefully to ensure sufficient rigidity and resistance to deflection.

Which Type of Linear Shaft Is Best?

The best shaft design depends on the application's mounting requirements, load conditions, and performance goals.

Tapped shafts are ideal when clean, secure end mounting is required.
Threaded shafts provide flexibility and easy installation.
Hollow shafts are best when reducing weight and improving motion efficiency are priorities.

Working with a knowledgeable shafting supplier can help ensure the selected shaft configuration delivers the proper balance of strength, precision, and long-term reliability for the application.

How Are Linear Shafts Mounted?

Proper mounting is necessary for shafting to be used as a linear guide. The most common shaft mounting methods are continuously and end supported.

What Is a Continuously Supported Shaft?

Continuously supported shafts are attached and supported along the entire length. They are used when loads are high.

What Is an End-Supported Shaft?

End supported shafts are supported at both ends and are used when loads are light.

What Materials Are Used for Linear Shafts?

Just as mounting comes into play for the best performance, the materials and coatings are as necessary. Most linear shafts are made of alloy or stainless steel, or aluminum linear.

When Should Alloy Steel Shafts Be Used?

Alloy steel provides superior durability.

When Should Stainless Steel Shafts Be Used?

Steel shafts can be used with typical linear bearing applications. Stainless steel shafts are suitable for a cleanroom environment or when introduced to severe conditions, such as high humidity or erratic temperatures.

So, the stainless steel shafts are well-suited where corrosion resistance is a top priority.

When Should Aluminum Shafts Be Used?

These shafts provide good electrical and thermal conductivity, high reflectivity, and oxidation resistance. [source]

What Loads Must Linear Shafts and Bearings Support?

Linear shafts and bearings may experience radial, axial, or combined loads. Understanding the direction and magnitude of these forces helps ensure proper shaft selection and longer equipment life.

A load can be applied to bearings in basically two directions. Axial bearings are designed to withstand force in the same direction as the shaft. Radial bearings are designed to withstand forces that are perpendicular to the direction of the shaft.

A shaft will try to push the bearing in the same direction in which the load moves.

Types of Loads

Radial Load - any direction perpendicular to the shaft axis. Radial loads act as right angles to the shaft (bearing's axis of rotation). It is when the load is vertical to the shaft due to gravity. A radial load can also be referred to as the "overhung load" because of how it may hang off the shaft.

Axial Load (also known as Thrust Load) - acts in the same direction as the shaft. It is considered when the load is parallel to the post.

Angular- These are designed to accommodate combined loads, acting radial and axial loads.

Can Linear Shafts Be Custom Machined?

Yes. Linear shafts can be custom machined to meet specific application requirements. Common machining operations include cutting, drilling, tapping, turning, and precision grinding.

There are many steps involved in machining a perfectly smooth and precise workpiece. Specially machined shafts may require drilling, tapping, turning and grinding.

Grinding is a machining process that is used to remove unwanted material. Turning involves the rotation of a workpiece while a cutting tool moves in a linear motion.

Drilling creates a round hole in the workpiece. Tapping is the action that makes a thread into the side of the hole.

Resources: Machining Process: Turning, Milling and Drilling, Drill and Tap Reference for CNC Machined Parts

How Do You Select the Right Linear Shaft?

Key Factors to Consider

- - Load requirements
  - Shaft length
  - Deflection concerns
  - Environmental conditions
  - Corrosion resistance
  - Mounting method
  - Bearing compatibility
  - Need for custom machining

If you're unsure which shaft is best for your application, BDS can help identify the proper material, dimensions, support method, and machining requirements.

Frequently Asked Questions About Linear Shafts

What is the difference between a linear shaft and a linear rail?

Linear shafts use round shafting and linear bearings, while linear rails use profiled guide rails and bearing blocks. The best choice depends on load requirements, accuracy needs, and available installation space.

What material is best for a linear shaft?

Alloy steel is commonly used for durability, stainless steel is preferred in corrosive environments, and aluminum may be selected when weight reduction is important.

Can linear shafts be cut to length?

Yes. Linear shafts can be cut, machined, drilled, tapped, or modified to meet specific application requirements.

How do I know if I need shaft support?

Longer shafts or applications with heavier loads often require continuous support to minimize shaft deflection and maintain accuracy.

Does BDS provide custom shafting solutions?

Yes. BDS supplies precision shafting and can provide value-added machining services including cutting, drilling, tapping, grinding, and other modifications to meet application requirements.

Selecting the right linear shaft is just as important as selecting the right bearing. Shaft material, support method, load requirements, and machining specifications all play a role in overall system performance and reliability.

At BDS, we help distributors and OEMs source precision shafting, custom-machined solutions, and hard-to-find motion components for demanding applications. Whether you need standard shafting, cut-to-length material, or specialized modifications, our team can help identify the right solution and get it shipped quickly.

Need help with a shafting application? Contact BDS today to discuss your requirements with one of our shafting and bearing specialists.