A guide to universal joints
Universal joints, also called uni joints, are mechanical components that connect two rotating shafts, allowing them to transmit rotary motion despite being misaligned. These uni joints are crucial for enabling flexibility and accommodating angular displacement between shafts. They ensure efficient power transfer even when the shafts operate at different angles. Although durable, universal joints typically need regular maintenance due to the wear they endure from continuous operation and load. In this guide, we’ll cover:
What are the types of universal joints?
Telescopic universal joints
Single universal joints
Single universal joint – unbored solid ends
Double universal joints
Double universal joints – unbored solid ends
Bellows
Applications for universal joints
What are the types of universal joints?
It’s worth noting that the term universal joint coupling is often used to mean a universal joint, but they’re not quite the same. A universal joint coupling specifically refers to the assembly that connects the two shafts, and incorporates the universal joint. A universal joint coupling is used in automotive drive shafts, industrial machinery, agricultural equipment, aerospace control systems, marine propulsion, robotics, renewable energy systems, and construction equipment.
Universal joints come in several types, each suited to specific mechanical demands and applications. These types address varying degrees of angular misalignment, load capacities, and performance requirements, making the right choice crucial for optimising system efficiency and durability. Achieving motion control often means integrating complementary components like lead screws or ball screws.
Telescopic universal joints
Telescopic universal joints combine the capabilities of a universal joint and a telescopic shaft. These joints consist of two yokes connected by a telescopic shaft, allowing for angular misalignment and accommodating changes in length. This design enables the joint to expand and contract to adjust to variations in distance between connected components.
Key features:
● Dual functionality – combines angular flexibility for misaligned shafts (like a double universal joint) with the adjustability of a telescopic shaft
● Handles both angular misalignment and changes in shaft length during setup
● Efficiently transmits torque between connected components
● Durable – Available in steel and stainless steel to withstand heavy loads
● Maximum bending angle per joint (typically 45 degrees)
● Pre-lubricated for long-lasting performance (check specific models for confirmation)
Single universal joints
Single universal joints offer rotational flexibility for misaligned shafts in a single axis. They transmit torque and rotation at angles, making them ideal for connecting non-parallel axles.
These joints excel at handling moderate angular misalignment while transmitting torque. They come in two bearing options: simple or needle rollers, both pre-lubricated for maintenance-free operation.
Key features:
● Accommodates angular misalignment (up to 45 degrees per joint)
● Transmits torque
● Maintenance-free (lubricated for life)
● Available in plain bearing or needle roller
● Quiet and smooth operation
● Durable for harsh environments (often made from steel or stainless steel)
Single universal joint – unbored solid ends
This uni joint distinguishes itself from standard single universal joints primarily in its design and application. Unlike typical single universal joints that often feature bored ends for shaft attachment, these joints are specifically made with solid, unbored ends. This enables you to design your own bore system.
Where standard single universal joints may prioritise ease of shaft attachment through bored ends, unbored solid ends offer flexibility. If a standard size isn't suitable, you can modify the joints to fit your specific size requirements. Ideal for industrial machinery.
Key features:
● Enhanced durability and strength – steel and stainless steel available
● Enables smooth transmission of torque and rotation between non-aligned shafts, accommodating up to 45 degrees of misalignment per joint
● High-speed capability – depending on the bearing, can support a maximum joint driving speed of 1000 rpm
● Designed for high-load environments
● Operates quietly and smoothly, minimising friction and wear for consistent performance over time
View our range of single universal joint – unbored solid ends
vDouble universal joints
Double joints are mechanical couplings used to transmit rotational motion between two shafts that are not aligned with each other. It consists of two single universal joints connected by an intermediate shaft, allowing for smoother power transmission and reduced vibration compared to a single universal joint.
These double joints are built to withstand heavy loads and deliver long-lasting performance, even in harsh working conditions. They can bend up to 45 degrees per joint, ensuring accurate, silent, and smooth operation.
Key features:
● Effectively transmits power even when shafts are not perfectly aligned
● Made from steel or 304 stainless steel for strength and corrosion resistance
● Designed to endure heavy loads and provide long-lasting performance in harsh environments.
● High flexibility – can bend up to 45 degrees per joint, ensuring versatile application
● Ensures silent and smooth functionality, reducing operational noise
Before installing, you might find it helpful to check out a guide by our experts, Bolts vs. screws: What’s the difference and when to use each.
Double universal joints – unbored solid ends
Double joints with unbored solid ends are engineered for applications requiring significant bending angles or when two shafts are offset. Their unique design makes them ideal for demanding tasks that need high-torque capacity and resistance to wear and tear, along with the ability to endure considerable misalignment angles. These double joints are designed to handle heavy loads and offer long-lasting performance in challenging environments.
Key features:
● Accommodates up to 45 degrees of bending per joint
● Designed to connect misaligned or offset shafts
● Handles demanding applications that require high torque
● Steel or 304 stainless steel for strength and corrosion resistance
● Withstands enormous loads and harsh working environments
● Ensures accurate, silent, and smooth motion.
● Maximum driving speed of 1000 rpm for ball-bearing joints, depending on bearing type
View our range of double universal joints – unbored solid ends
Bellows
Bellows are used for flexibility, sealing, and protection in various applications. They’re designed for use with universal joints and available for double joints. They can expand and contract in response to movement and pressure changes. These bellows effectively protect against dirt, dust, moisture, and other contaminants, ensuring the longevity of the application. When filled with grease, they provide long-term lubrication for friction bearings. Installation requires securing both ends with two cable ties (available separately).
Key features:
● Adapts to movement and pressure changes
● Protects applications from dirt, dust, moisture, and other pollutants
● Accommodates thermal expansion, vibration, and misalignment
● Can be filled with grease for sustained lubrication of friction bearings
● Made from PVC and rubber for durability and flexibility
Applications for universal joints
Without universal joints, rigid connections would require precise alignment between shafts, which is often impractical due to space constraints, vibration, thermal expansion, or the need for movement. Below is a table highlighting common applications where universal joints are most often used.
| Type | Industrial machinery | Conveyor systems | HVACs |
|---|---|---|---|
| Telescopic | ● | ● | |
| Single | ● | ● | |
| Single – unbored solid ends | ● | ||
| Double | ● | ● | |
| Double – unbored solid ends | ● | ● | |
| Bellows | ● | ● |
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If you’re not quite sure which universal joint will work best for your application, our experts are always happy to advise you.
You might need fasteners for your application. See our experts’ Guide to one-touch fasteners.
You’ll also find it helpful to check out our guides, Choosing the right captive screws and Titanium fastener Grades: A comprehensive guide.
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Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.