When steel meets aluminium: tolerance rings compensate for thermal expansion
Shaft–hub connections are among the classic design tasks in mechanical engineering. Bearings, gears or rotors are often secured in housings via press fits. However, this joining technique reaches its limits when different materials meet and temperature fluctuations occur. So how can the thermal expansion of mating components be compensated easily? This is where tolerance rings show their strengths.
When materials behave differently
In many machines, shafts and bearings are made of steel. Housings, by contrast, are often made of aluminium, magnesium or plastic for reasons of weight, cost or manufacturing. This material combination makes sense from a design perspective, but it comes with a physical challenge: the materials expand by different amounts when temperatures change. While steel exhibits only moderate thermal expansion, light metals change their dimensions much more significantly. If the operating temperature rises, an aluminium housing, for example, can expand more than the steel component seated inside it. If the temperature drops, the housing contracts correspondingly more. For classic press fits, this means the forces in the joint change. The fit can loosen or excessive stresses can build up. In the long term, both can lead to functional problems, for example due to micro-movements, increased wear, or damage to the bearing and housing.
Tolerance rings provide a robust solution for this situation. Their characteristic wave-shaped structure acts like an elastic interface between shaft and hub. During installation, the ring creates a defined preload between the components. At the same time, it can deform elastically and thus compensate for changes caused by different thermal expansion. This keeps the connection stable and functional even when temperatures vary. A typical example is electric motors, where steel bearings are mounted in aluminium housings. While the housing heats up during operation and expands more, the tolerance ring ensures the connection remains reliable.
Materials for demanding operating conditions
For our tolerance rings, we use high-quality materials.
As standard, we use corrosion-resistant spring steel 1.4310 (X10CrNi18-8). The material is processed as cold-worked strip and does not require any further post-treatment. Thanks to its high strength and good corrosion resistance, it is also suitable for applications where moisture or chemical influences play a role. The maximum recommended operating temperature is 250°C; temperatures of up to 300°C are also possible for short periods.
For particularly demanding applications, Dr. TRETTER also offers tolerance rings made of Hastelloy. These can be used at operating temperatures from minus 70°C to plus 480°C, making them suitable even for extreme environmental conditions. We can usually deliver even smaller quantities within four to eight weeks.
Tolerance rings can do even more
Are you looking for a way to reduce noise? Or should assembly be quick and easy? Then tolerance rings are the ideal solution. These versatile components also provide valuable support in reducing oscillations/vibrations, limiting and transmitting torque, transmitting axial forces, compensating for misalignment and centre offset, or bridging large tolerances of mating components. This enables robust and cost-effective solutions for numerous industrial applications.
