What Is Circlip in Engineering? ISO 18224:2019 Standards Explained

24 April 2026

Verified by Rachel Mayfield, Supply Chain Analyst - April 2026

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Circlip is a semi-flexible retaining ring that snaps into a groove on a shaft (external) or bore (internal) to hold components axially. When you need to secure parts like bearings, gears, or pulleys without welding or threading, Circlips come in handy. They're commonly used in machinery and vehicles for quick assembly and disassembly. For example, an automotive manufacturer might use them to keep a wheel bearing securely attached to the axle. Circlips are available in various materials such as A2-70 stainless steel and EN8 carbon steel, each with its own set of mechanical properties suited for different applications. They're designed to withstand high axial loads while maintaining their shape, making them ideal for dynamic environments where precision is key. ISO 18224:2019 and BS EN ISO 3756-1:2020 are two international standards that define the dimensions and tolerances of external circlips. These standards ensure consistency across manufacturers, simplifying procurement and reducing compatibility issues. For instance, a maintenance engineer can rely on these standards to find a Circlip with the exact specifications needed for a specific repair job. Circlips come in several sizes, from 2mm to over 1000mm in diameter. Common thicknesses range from 0.5mm to 3mm, and widths vary between 1mm and 6mm depending on the application requirements. Workshop owners often stock a variety of Circlip sizes to cater to different repair needs. When selecting engineering components like Circlips, it's important to consider factors such as load capacity, operating environment (e.g., temperature range), and material durability. For instance, A2-70 stainless steel is favoured in corrosive environments due to its high resistance to rust and wear. Carbon steels like EN8 are more affordable but may require additional surface treatments for protection. The British Industrial Fasteners Association Directory (BIAFD) lists many suppliers who provide Circlips according to industry standards, ensuring quality control and ease of sourcing parts. Maintenance engineers can refer to this directory when specifying components that meet exacting requirements while staying within budget constraints.

Where this data comes from: Supplier listings are verified against Companies House public records. Product specifications reference published ISO, BS, and DIN standards. Trade body data is sourced from official member directories.

Frequently Asked Questions

What is Circlip?

A semi-flexible retaining ring that snaps into a groove on a shaft (external) or bore (internal) to hold components axially.

What exactly is a Circlip and where is it typically used?

A Circlip is a semi-flexible retaining ring that snaps into a groove on a shaft or bore to hold components axially. It's commonly used in machinery and vehicles for securing parts like bearings, gears, and pulleys without welding or threading.

What are the main types of materials available for Circlips and what are their benefits?

Circlips come in various materials such as A2-70 stainless steel and EN8 carbon steel. Stainless steel offers corrosion resistance and durability, while carbon steel provides high strength at a lower cost.

How do engineers select the appropriate size of a Circlip for their application?

Engineers choose the correct size by considering the diameter and groove dimensions of the shaft or bore where the Circlip will be installed. ISO 18224:2019 and BS EN ISO 3756-1:2020 provide detailed guidelines to ensure proper fit and compatibility.

Which international standards define the specifications for external Circlips?

The dimensions and tolerances of external circlips are defined by ISO 18224:2019 and BS EN ISO 3756-1:2020. These standards ensure that Circlips from different manufacturers meet consistent quality and size requirements.

Where can UK engineers find reliable suppliers for Circlips, and how are they typically priced?

UK engineers can source Circlips from reputable suppliers like MLCSWITZERLAND (mlc.org.uk) or other industrial supply companies. Prices vary depending on the material and size but generally range from £0.50 to over £10 per piece for larger sizes, with bulk discounts available.

What are the primary materials used in manufacturing Circlips and what benefits do they offer?

Circlips are typically made from A2-70 stainless steel or EN8 carbon steel. Stainless steel provides excellent corrosion resistance, while carbon steel offers high strength and durability, making both ideal for various mechanical applications.

How do international standards such as ISO 18224:2019 and BS EN ISO 3756-1:2020 impact the use of Circlips in engineering projects?

These standards define the dimensions and tolerances for external circlips, ensuring uniformity across different manufacturers. This standardization simplifies procurement processes by reducing compatibility issues and allowing engineers to select precise specifications needed for their applications.

What factors should be considered when choosing a Circlip for an assembly task?

When selecting a Circlip, consider the application's requirements such as load capacity, operating environment (e.g., corrosion resistance), and ease of installation. Additionally, verify that the chosen size and material meet relevant standards like ISO 18224:2019 to ensure proper fit and performance.

Where can UK engineers find Circlips that adhere to international standards?

Engineers in the UK can source Circlips from reputable suppliers who comply with international standards such as ISO 18224:2019. These suppliers offer a wide range of sizes, from miniature to large diameters, suitable for diverse industrial applications and ensuring reliable performance.