Conical elastic washers fitted alongside ball bearings to retain them, providing an elastic support that absorbs vibration and eliminates the noise caused by spinning without axial load.
The disc spring also acts as a compensator for the thermal expansion produced by the heating and cooling of the shaft on which the bearing is mounted, significantly increasing bearing service life.
Its key advantage is the minimal force variation across a wide range of its travel: the spring supplies the force needed for correct axial retention and keeps it within a suitable range, without overloading or loosening the bearing.
There are two types of ball bearing disc spring. Both share the same operating principle — working in the regressive zone of their characteristic curve — but they differ in the level of preload force and in how finely they behave.
A conical elastic washer whose force vs. deflection curve is regressive, allowing force variation to stay low relative to its deflection.
A variant of the above with slots on the inner circumference. It delivers an even lower preload force and the minimum force variation for the greatest deflection. Suited to small-sized bearings.
Axial preload is the internal load applied to a bearing when the system is at rest. Managing it correctly directly determines the service life, noise and stiffness of the assembly.
The ball bearing disc spring solves this problem because it works in the flat zone of its load-deflection curve: small dimensional changes due to temperature or wear barely alter the force exerted. The engineer designs for a stable preload, not for a rigid geometry.
Tell us about your use case and our engineering team will help you choose the optimal solution.
Unlike a conventional helical spring (linear behaviour), the ball bearing disc spring works in the regressive zone of its characteristic curve, where stiffness decreases with deflection.
In the designed working zone (typically between 75% and 100% of total deflection), the ΔF/Δs ratio is very low:
This behaviour is impossible to achieve with a rigid spacer or an adjusting nut, which fix the position but not the force.
The regressive zone appears when the h/t ratio (free cone height over disc thickness) exceeds a value of around 1.41. Ball bearing disc springs are specifically designed to work in this zone.
In most industrial applications, the shaft and the housing have similar but not identical thermal expansion coefficients, and the thermal mass of each component means they heat up and cool down at different rates. The result is axial dimensional changes of tenths of a millimetre that, on a rigid preload system, can generate load variations of hundreds of Newtons.
With a well-selected ball bearing disc spring, those 0.138 mm of dimensional change produce a force variation below 10–15% of the nominal preload. With a rigid system, the same expansion can generate a preload increase of several kN, with a risk of overloading the bearing.
| Parameter | Value |
|---|---|
| Shaft material (42CrMo4 steel) | α = 11.5 × 10⁻⁶ /°C |
| Length between supports | 300 mm |
| Temperature variation | ΔT = 40 °C |
| Resulting axial expansion | Δl ≈ 0.138 mm |
Ball bearing disc springs are found in equipment where the combination of precision, variable temperature and long service life is a design requirement.
High-speed spindles are extremely sensitive to preload variations. Precision spindle manufacturers use disc springs for tandem angular contact bearings, where the preload must remain constant from cold to operating temperature. The alternative — manual adjustment with a nut — requires periodic recalibration and is a source of machining errors.
In induction motors and servomotors, the free-end bearing (non-drive side) works with an axially floating support. The disc spring in the motor end cover provides the minimum preload needed to prevent race skidding without restricting the axial expansion of the rotor shaft.
Centrifugal pumps and screw compressors generate axial loads that vary with flow rate and pressure. The disc spring acts as a preload element that ensures contact in the thrust bearing even under light-load conditions (start-up, no-load operation).
In helical gear reducers, the axial component of the meshing force must be absorbed by thrust or angular contact bearings. A disc spring on the shaft's floating support ensures this bearing stays loaded across the entire operating range, preventing skidding (slippage of the rolling elements).
Bogies and traction axles work under extreme temperature conditions (from −40 °C to +80 °C) and require materials and designs that maintain function across that whole range. In these applications, special alloys are often used (see the materials section).
When an application requires a greater force than a single washer can provide, stacking in parallel is possible: the spring force increases in proportion to the number of springs used. The hysteresis caused by friction between the pieces will have an effect on the force vs. deflection curve.
When the available axial space does not allow scaling up to a larger-diameter spring, or when a force greater than the catalogue offering is needed for the external diameter constrained by the bearing.
With 2 springs in parallel, the force doubles while keeping the deflection. With 3, it triples. The useful working travel does not change, but the hysteresis increases.
For high-precision applications (machining spindles, instrumentation), stacking more than 2 pieces in parallel can introduce unacceptable force hysteresis. In these cases we recommend selecting a larger-diameter spring or a different h/t ratio. Consult our engineers.
Ball bearing disc springs are made from high-quality spring steel. They can also be made from other materials to offer resistance to corrosion, to high or low temperatures, or for applications that require a non-magnetic material.
For this, stainless steels and alloys such as Inconel or Nimonic 90 are used. As these steels have a different modulus of elasticity, the spring calculation will change and, in some cases, the pieces must be made with a different thickness to meet the specifications of the original spring.
For applications with an operating temperature above 200 °C or in corrosive environments, material selection is critical to the spring's service life. Consult us before specifying.
| Material | Standard · designation | Max. continuous temp. | Corrosion resist. | Magnetic | Typical application |
|---|---|---|---|---|---|
| Spring steel | 51CrV4 / DIN 17221 | ~200 °C | Low (coating) | Yes | General industrial use |
| Stainless steel | 1.4310 (AISI 301) | ~300 °C | High | Weak | Food, chemical, marine |
| Stainless steel | 1.4568 (17-7 PH) | ~350 °C | High | Weak | Aerospace, high strength |
| Inconel 718 | UNS N07718 | ~650 °C | Very high | No | High temperature, aerospace |
| Nimonic 90 | UNS N07090 | ~850 °C | Very high | No | Turbines, cryogenic |
Selecting a ball bearing disc spring requires determining the following starting parameters. With this data, our team can recommend the most suitable catalogue model or calculate a special piece if the standard does not meet the requirements.
Technically it is possible if the dimensions and force curve are compatible. However, ball bearing disc springs are specifically designed to work in the regressive zone of their curve, with h/t ratios optimised for this purpose. A standard DIN 2093 spring may behave more linearly, which is not optimal for bearing preload applications. Consult us.
Lubrication reduces the spring's hysteresis. Under dry conditions, friction between stacked springs (in parallel) increases hysteresis and can produce differences of up to 20–30% between the loading and unloading curves. With lubricant (grease or oil), this difference is significantly reduced. For high-precision applications, always specifying lubrication is recommended.
In static or quasi-static preload applications (a bearing with few load reversals per day), the practical service life is indefinite if the working stress does not exceed the material's fatigue limits. In dynamic applications (continuous vibration, frequent load cycles), service life depends on the deflection amplitude and must be calculated according to the criteria of DIN 2093 / DIN EN 16983.
For humid environments or mild corrosion: phosphating + oil or zinc chromate. For marine or acidic environments: 1.4310 stainless steel or zinc-nickel coating. For extreme cases: Inconel or Nimonic with no additional coating.
Tell us about your use case and our engineering team will help you choose the optimal solution.
