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Key Considerations for Universal Joint Selection

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Carefully specified universal joints not only ensure proper fit and function but can prevent scores of machinery problems further down the road. Joint selection should start with assessing the operating conditions, with all relevant factors communicated to your sales representative. Environmental exposure to fluids, abrasives, extreme temperatures or pressure, for example, may necessitate special materials, finishes or design modifications. The nature of operation must also be taken into consideration, since applications with frequent stops generally exert a greater torque than continuous operations.

The angle and extent of misalignment between the driving and driven shafts will determine the joint selection for single and double joints or drive shafts. Single joints can compensate for moderate misalignments and angles (up to 45° for Belden joints), while double joints or drive shafts are suitable to bridge more pronounced displacements and angles of up to 90°.

In addition to the operating angle, rotational speed (RPM) and torque applied are two other key factors influencing joint selection and durability. The higher the combined effect of angle, torque and RPM, the greater the stress on the joint. Higher operating angles result in increased movement and wear between the bearing components. Excessive torque can cause the joint to break, while an excessive speed and angle at an acceptable torque may cause lubrication failure, which in turn leads to increased friction, heat generation and premature wear.

Friction and heat generation are the adverse outcome of high-speed operations that can be addressed by proper design selection. The roller-bearings of needle-bearing joints operate with low friction and can be permanently pre-lubricated and sealed. This low friction ensures minimal play over time, making needle-bearing joints highly suitable for continuous operations at high RPM and sustained precision.

Friction-bearing joints (also referred to as pin & block joints) are an ideal and cost-effective solution for handling higher torque at moderate speeds. However, they operate with significant friction and heat generation within the moving components. Unlike needle-bearing joints, friction-bearing joints are difficult to pre-lubricate. Therefore, proper manual re-lubrication should be delivered with oil drip, regular re-lubrication or lubricant-retaining boot covers. Boot covers will also protect the moving parts from debris and other contamination.

Belden’s friction-bearing joints come in three design types: heavy duty, high strength and leveler strength. Heavy-duty joints are suitable for many standard applications. High-strength joints are supported by stronger pins and a rivet for higher-torque applications. Our leveler joints are designed with a reinforced yoke profile, delivering extreme load-bearing capacity.

While high-grade alloy steel is Belden’s preferred material for standard applications, our components can be further enhanced by special finishing and coating processes for increased strength, machinability, corrosion resistance and other desired qualities. Standard stainless steel such as 316L is suitable for general corrosion resistance; however, other grades of stainless and specialty materials (e.g. Super Duplex Stainless, Titanium, Bronze) are available to improve the component’s mechanical properties.

With these thoughts in mind, please gather as much information as possible about the operating environment and application and discuss them in detail with your application specialist. For additional information on universal joint selection and customization, please contact us at (708)344-4600 or