Shaft-hub connections without a key: Simpler design, more economical manufacturing
Keyed connections are widely used in mechanical engineering. They reliably transmit torque and are used, for example, in gears, belt pulleys, or couplings. However, they require additional machining steps on the shaft and hub. Depending on the application, a connection using a tolerance ring can be a simpler and more economical alternative – both for new designs and for existing production series.
Less machining effort, lower costs
In a classic keyed connection, torque is transmitted by positive locking. To achieve this, both the shaft and the hub must be fitted with precisely matched keyways. This increases manufacturing effort. In addition, the keyways reduce the material cross-section, which can affect the load capacity of the components. Tolerance rings, on the other hand, enable a frictional connection. Their characteristic wave profile deforms elastically during press-fitting, generating a defined contact pressure between shaft and hub. This allows torque and axial forces to be transmitted. With a suitable design, keyways can be eliminated entirely. In the simplest case, a smooth shaft and a smooth bore are sufficient. At the same time, larger manufacturing tolerances of the mating parts can be compensated for. Assembly is straightforward, and with the appropriate design, the connection can be released again.
However, the cost of the connecting element alone is not what determines overall economic efficiency – the entire manufacturing and assembly effort must be considered. Savings can be particularly significant in series production. A calculation example from our practice illustrates the potential: when mounting three toothed belt pulleys on an 8 mm diameter shaft, a keyed connection with a 12 mm long and 3 mm wide key achieves a transmittable torque of 5.8 Nm. A comparable tolerance ring transmits 5.7 Nm. In this application, the tolerance ring reduces costs by around 38 percent.
Which applications are tolerance rings suitable for?
In addition to the applications already mentioned for keyed connections, there are numerous other uses for tolerance rings, for example in pump rotors, fan wheels, or driven conveyor rollers. Tolerance rings also perform important connecting functions in robotics and electric drive systems. Thanks to their elastic properties, they can also compensate for differing thermal expansion of the mating parts and reduce oscillation and vibration.
However, not every tolerance ring is suitable for every application. Important selection criteria include the torque to be transmitted, the load conditions, the required concentricity, and the assembly conditions. For very high torques or special loads, positive-locking connections may be the better choice. For this reason, we work together with our customers to determine which connection technology best meets their specific requirements.
Switching to tolerance rings in existing production series
Switching to a tolerance ring can also be worthwhile for existing production series. This requires careful review to ensure that the new connection meets all technical and quality requirements. We support development, quality, and purchasing teams throughout the entire conversion process: from reviewing existing specifications and conducting feasibility analyses, to selecting suitable materials and geometries, through to sample production including an inspection report. We then support the transition into series production. Our Swiss manufacturing ensures reproducible quality, transparent lead times, and reliable long-term supply.
Express service for short-term testing
When time is short, we deliver custom tolerance rings within 48 to 72 hours, including inspection, test report, and direct coordination with our engineering team. This allows us to support you with short-term tests and validations, design changes, and the development of new assemblies and prototypes.
Looking to replace a keyed connection or simplify your manufacturing process? Talk to us. Together, we’ll find a technically and economically sound solution.
