Spline couplings – the wedge-shaped shaft-hub connection with reduced notch effect
Hollow keys are standardized machine elements used to create a positive and friction-based connection between a shaft and a hub. Hollow keys belong to the family of keyed connections, but differ in design from flat and tapered keys due to their contoured underside. This geometric modification reduces the notch effect in the shaft, making splined keys a particularly suitable alternative for dynamically loaded applications. A wide variety of different materials can be used for their manufacture, all of which are available from our stock—and we naturally ensure that the splined keys are manufactured in accordance with DIN 6881 and meet the highest quality standards. If required, hollow wedges in our product range are available with or without heat treatment. Thanks to our many years of experience in CNC machining, we know exactly what matters in the production of hollow wedges and can also quickly and effectively produce custom-made solutions for you.
What is a hollow wedge?
Hollow keys are wedge-shaped connecting elements with a rectangular cross-section and a hollow or radiused underside. As a result, the hollow key does not rest flat against the shaft groove but rather in a linear fashion. Hollow keys are standardized according to DIN 6881, so that dimensions, key angles, and recommended applications are already defined. However, if needed, custom and special designs according to customer specifications are also possible to provide you with maximum flexibility when operating your machines.
Interesting facts about our hollow wedges
Available sizes
| Width | b | 6 - 36 mm |
| Height | h | 2 - 9 mm |
| Length | l | 20 - 400 mm |
Typical standards and materials for hollow keys
Hollow keys are manufactured in accordance with DIN 6881—a standard that defines the width, height, and length of the keys, thereby ensuring international applicability. The key angle is specified by the standard, enabling reproducible clamping in all types of machines and equipment. Common materials used include quenched and tempered steel (e.g., C45), case-hardened steel, or—in special cases—stainless steel. The shaft groove is less critical for hollow keys than for flat keys, as full contact is not required. Nevertheless, it is of the utmost importance to ensure optimal custom sizing during manufacturing to guarantee a secure fit.
How do hollow keys work?
Hollow keys function much like other keyed connections by transmitting torque through a combination of form fit and force fit. When the key is driven into the machine, the key angle creates radial pressure between the shaft and the hub. Unlike other key types, however, the hollow underside ensures that the contact area with the shaft is reduced. This reduces the notch stress within the shaft, which has a positive effect on fatigue strength. Nevertheless, the clamping effect is maintained.
The Advantages of Hollow Keys
Hollow keys are a good solution when reduced notch stress within the shaft is desired. They are ideal for alternating loads and are therefore a sensible alternative to other keyed connections. The keyway effect enables high torque transmission while simultaneously reducing the risk of shaft cracks—making hollow keys stand out as an alternative to flat keys, particularly when dealing with dynamic loads.
As a result, hollow keys are primarily used in mechanical and plant engineering, but also in gear and drive technology. Applications with high alternating and vibrational loads, as well as designs with shafts prone to fatigue, can be efficiently supported by hollow keys.
Buy hollow keys to DIN 6881 and custom-made products online
Hollow keys to DIN 6881 are considered high-performance machine components that enable a heavy-duty shaft-hub connection. The strength of the shaft is clearly the primary focus of this design, allowing for high torque transmission and effectively reducing notch stresses. If you’d like to buy hollow keys to DIN 6881 or custom-made products online, you’ve come to the right place!
As a specialized manufacturer in CNC machining, we’ve been in business since 1955 and can draw on extensive expertise that we continue to utilize and expand to this day. Our well-stocked warehouse carries nearly all standard materials, allowing us to process not only standard orders quickly and efficiently but also to handle custom requests with ease.
If you have any questions about our hollow keys or would like a no-obligation quote, simply contact us via our contact form.