Woodruff keys explained

All you need to know about Woodruff keys

In this article, we are going to talk about Woodruff keys, also known as half-moon keys, looking at their technical specifications, the manufacturing process and example applications. Although they may appear small and insignificant, this part plays an essential role in the transmission of movement and power between shafts and machine components. We manufacture our Woodruff keys to DIN 6888 or NFE 22179 standards, and can also produce custom Woodruff keys based off of our clients' own designs.

‍What is a Woodruff key?

Woodruff keys, also called half-moon keys, are fasteners used in mechanical transmissions to ensure precise alignment between the shaft and the transmission element. They are semi-circular parts with a flat section and a curved section.

The shaft has a special groove called a key seat or recess into which the key is inserted. The key seat, as well as the key itself, has a characteristic rounded shape. The key must extend slightly beyond the key seat to allow the mortise found on the transmission element to be inserted.

Their circular shape allows the load to be distributed evenly over the surface of both the shaft and the transmission element, reducing the risk of damage or deformation.

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How are keys made?

1. Rolling & drawing: The raw material, usually steel or stainless steel, is cold rolled and drawn to achieve a semi-circular "half moon" profile.
2. Cutting: Once a semi-circular profile has been obtained, the parts are cut using circular saws to get the desired width.
3. Grinding: Carried out to achieve the precise width dimensions.
4. Vibratory finishing: After milling, keys may have burrs and a rough surface. To improve parts' surface condition, they undergo a vibratory finishing process for a high-quality finished product.
5. Quality control: Finally, before being used or sold, round-end keys must go through our quality control procedure to ensure that they meet the required specifications and industry standards. This can include visual checks, dimensional measurements and other tests to ensure that the keys comply with quality requirements.

It should be noted that the exact manufacturing steps may vary depending on each client's particular requirements.

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When should Woodruff keys be used?

Woodruff keys are mostly used in applications with a small shaft diameter and low torque transmission. Thus a key with a diameter equivalent to (or slightly greater than) the shaft is chosen. The Woodruff key is also used when precise alignment is needed, as its semi-circular or half-moon shape allows for a precise fit with minimal slippage and sufficient alignment.

Woodruff keys can be found in a wide range of areas, including machine tools, transmission systems such as gearboxes, lifting equipment and automobiles.