How to Select the Right Linear Shaft for Industrial Applications

What are Linear Shafts

Linear shafts are also known as linear guide shafts, linear rods, or linear motion shafts. They are rod-shaped machined bars on which linear bearings move. The shaft's one or both ends usually possess mounting features, such as threads, to allow connection with other components or systems. These elements are critical in creating a linear guide system that is essential in supporting straight-line motion in various mechanical and industrial equipment.

How do Linear Shafts Operate?

Linear shafts are paired with linear motion components, such as linear bushings, to form a precise linear motion system. Linear shafts are incorporated with ball bushes or similar components to enable linear motion. In these systems, a linear bearing shaft serves as the guiding structure, ensuring precision and stability in automation, robotics, and industrial machinery. Components affixed to the guide shafts allow the system to move smoothly along the shaft's axis with low friction. When paired with ball bushes, the system only transmits linear motion, which allows direct and not moment loads. Alternatively, the shafts can be paired with components like ceramic bushes to generate rotary motion systems.

Classification

Linear shafts are classified according to their material, bar configuration categories, and surface finish.

1. Categories

Categories of Shaft bar configuration include the shaft type, shaft end shape, shaft machining, and product shape filtering.

Linear Shaft – solid, Both Ends Stepped (Unmachined) /Both ends with internal Thread, g6 tolerance

Type: Solid guide shaft

Categories: Both Ends Stepped

Shaft machining: unmachined shaft

Shaft tolerance: g6

2. Material

Different materials are used to develop linear guide shafts due to their extensive range of applications in different industries. Therefore, a range of metals is required to produce an optimal shaft for the desired linear motion. The material types for linear shafts include:

Stainless steel

· Strong, reliable, and durable

· Requires minimal maintenance, thus lowering costs

· Moderate corrosion resistance. Can withstand harsh environmental conditions like humidity or harsh chemicals.

· They are commonly used in the automotive industry and medical equipment

Linear Shaft – Solid, Ends customizable, g6/f8 Tolerance

Tolerance of shaft: f8, g6

Material: S45C, SUJ2, SUS304, SUS440C

Surface finish: None, Hard chrome plating

Type: Solid guide shaft

Categories: Free Choice Type for Shaft Ends

Carbon steel

· It is strong and durable.

· It has lowered weight.

· It has good wear resistance and hardness.

· Its hollow design reduces weight and allows fluid, gas, or wiring to pass through, making them ideal for pneumatic and hydraulic automation systems.

· It offers smooth linear motion when paired with a linear ball bushing

· Applied in food processing and medical equipment

Aluminium

· It is corrosion-resistant. Its oxidation resistance reduces the need for regular maintenance.

· Excellent electrical and thermal conductivity

· Reduced weight thus increasing versatility

· Applications include construction, medical, oil and gas systems

3. Coating

Coatings on linear shafts provide protection and help improve the shaft's durability. Several materials are usually used for the shaft's coating.

i. Hard Chrome: enhances the shaft’s resistance to wear and abrasion for steel

ii. Black oxide: corrosion resistant, reduces light reflection, making them ideal for optical and laser-guided automation systems.

iii. Ceramic:  Increases resistance to corrosion and is perfect for aluminum shafts used in high-friction environments due to its enhanced wear resistance.

iv. Electroless Nickel: enhances corrosion resistance and wear for aluminum through additional hardening

Linear Shaft – Solid, Straight, g6 Tolerance

Class of precision: General class

Tolerance of shaft: g6

Material: SUJ2, SUS44OC, S45C

Surface finish: Hard chrome plating

Product shape filtering: Straight bar type

Type: Solid

Categories: Straight bar type

Shaft end shape: Unmachined Shaft End

Shaft machining: unmachined shaft

Selecting the correct linear shaft

A good linear shaft selection should be appropriate for your desired linear motion. Selecting the right linear shaft ensures durability and optimal performance in a guide system. The following factors are crucial for shaft selection:

1. Application requirements

Application requirements, such as load capacity, speed, and environmental conditions, should be highlighted.

2. Shaft Material

The shaft material choice should be evaluated for application-specific requirements. When choosing the correct material, like stainless steel, consider factors such as corrosion resistance or weight.

3. Shaft Diameter

The shaft diameter must support expected radial and axial loads while minimizing deflection. Typical diameters range from 8mm to 50mm, with hardened steel shafts preferred for high-load applications.

4. Shaft Hardness

Shaft hardness depends on the nature of the application. Hardened shafts (Rockwell C 58-62) resist wear and deformation under high loads, making them ideal for high-speed automation, robotic arms, and CNC machining centers. They can also support higher loads, retain surface finish, and ensure dimensional stability.

5. Tolerance Class

Consider the tolerance class associated with the shaft. You should opt for the tolerance class, which aligns with the application's accuracy requirements.

6. Load type

Consider the types of loads linear shafts are designed to support when making a selection. Think about the load types linear bearings and shafts are designed for, like axial, radial, or both.

Frequently Asked Questions for Linear Shafting

1. Do Linear shafts only transmit linear motion?

A pairing of linear shafts with ball bushes only transmits linear motion. However, when a linear shaft is paired with a component such as ceramic bushes, it can be used for rotary motion applications.

2. What does tolerance class mean in linear shafts?

The tolerance class indicates the allowable dimensions for the linear guide shaft's diameter.

Conclusion

Linear shafts paired with mechanical components like ball bushings create a linear guide system in industrial equipment. Linear shafts are categorized according to their material, surface finish, and bar configuration. The selection of a linear shaft depends on the application's requirements, shaft material, load type, shaft hardness, and tolerance class. The appropriate selection of a shaft has immense effects on the system's functionality and reliability.

View our linear shafts

Need high-precision linear shafts for your industrial application? Browse our extensive selection, explore custom machining options, and download free CAD models to streamline your design process. The JLCMC website has various categories of linear shafts to help you select the one suitable for your application. Our products and services are characterized by high-quality and extremely competitive processes. Enjoy our customization options and free CAD downloads to scrutinize the product. Our experts are always ready to offer assistance with your linear shaft selection.