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Adjustable Bearing Preload Solutions


adjustable bearing preload solutions

Angular roller bearings and ball bearings in an assembly typically require preloading in order to maintain a minimum designed axial force in the assembly. The minimum force is called the bearing preload and is designed to overcome the stack up of tolerances within the assembly and ensure no slop or gaps exist for a smooth and tight rotation.

There are many options available to the designer to compensate for the assembly's tolerances and achieve the desired preload force.

stop nuts

Threaded Systems

Preload adjusted by a threaded stop nut or bolt.

  • Benefits: preload is infinitely adjustable and able to be serviced in the field with minimal stocked parts.
  • Drawbacks: Preload amount is limited and dependent on torquing to specification. Threaded systems are also expensive by comparison

single thickness shims

Single Thickness Shims

Preload adjusted by displacing the gaps with a shim of the required thickness during assembly

  • Benefits: Simple and inexpensive design, and maintains constant preload between service intervals.
  • Drawbacks: Requires multiple stocked shim thicknesses to achieve the proper force during assembly.

coil wave springs

Springs (Conical, Coil/Compression, Wave)

Preload achieved by a spring and is dependant on the spring "K" and is only adjustable by replacing the spring with a different strength or configuration.

  • Benefits: Simple design and allows small yield during impact.
  • Drawbacks: Dissipating preload as spring fatigues, and allows yield during impact which may be detrimental to assembly (such as with a ring and pinion meshing gear set). Difficult to adjust.

surface bonded shims

Surface Bonded Laminated Shim Pack

Preload is achieved using the same method as a single thickness shim, but a glued, multiple-layer Shim pack is used to adjust the thickness at the point of assembly

  • Benefits: Simple and inexpensive design, maintains constant preload between service intervals, and allows for easier service in the field with less parts stocking.
  • Drawbacks: Sometimes it is difficult to peel layers, and discarded layers must be scrapped.

edge bonded shims

Edge Bonded Shim Set

Preload achieved with multiple layers of Shims, but the Shims are held together only by their edges making peeling to the desired thickness relatively simple.

Benefits: Easy to peel layers. Simple and inexpensive design, maintains constant preload between service intervals, and allows for the easiest service in the field with less parts stocking. Unused layers may be used in a different assembly.

Edge bonded shim sets are ideal for bearing preload applications and have key benefits over more conventional and laminated types of shims. The main difference between an edge bonded shim set and a laminated shim pack is the method of attachment between each layer of material.

  • Laminated shim packs are adhered throughout the entire surface between each layer of material and the layers are pressed together to cure much like how a particle board is manufactured.
  • The layers of an edge bonded shim set are first pressed together, and then adhered by the edges of the shim's profile. This allows for a much easier separation of the layers in the field.

Advantages Of Edge Bonded Shim Sets

Overview of Benefits: Easy to peel layers. Simple and inexpensive design, maintains constant preload between service intervals, and allows or the easiest service in the field with less parts stocking. Unused layers may be used in a different assembly.

Further Advantages

    • Unused layers can be saved for later as no deformation occurs during peeling
    • Edge bonded shim sets have more versatility with size and shape, allowing any shaped design, large or small, to be manufactured.
    • Edge bonded shim sets provide a more accurate and consistent preloading throughout the service life of the assembly without requiring a precise torque set.
    • Provides the most cost-effective solution, especially for repairs or service, compared to any angular bearing preload system.
    • Materials used for edge-bonded shims are less expensive - along with reducing costs with reusable removed layers.
    • Safety improvements are realized because no knife is required to remove edge-bonded layers.
    • Edge-bonded shim sets offer safe adjustment in seconds rather than time consuming and difficult to peel surface bonded laminates.

The following case study illustrates the benefits of SPIROL Edge Bonded Shim Set solutions in a manufacturing application

coil wave springs

Case Study:

A military ground assault vehicle manufacturer approached SPIROL to provide quick delivery of adjustable shim packs for spacing of armored vehicle door hinges. The spacing is critical for the welding process, providing proper sealing and locking engagement of the door systems.


The customer designed an adjustable shim pack based on surface bonded shim material requiring 94 layers of 0.0002" thick laminates. Because of the size and configuration of the parts, surface bonded materials were problematic in cost, the amount of time needed for dimensional adjustament, as well as a long lead-time required for manufacturing.

SPIROL Solution:

SPIROL application engineers worked with the customer to determine the required adjustment and developed three edge-bonded shim set proposals. The Customer evaluated the advantages and selected a proposal offering safe, quick adjustment, a 70% cost reduction, and a short manufacturing lead-time. SPIROL provided the solution without tooling cost using SPIROL's tool-less manufacturing technology.

SPIROL offers free samples and application engineering support.

SPIROL manufactures non-threaded types of bearing preload systems including Disc Springs, Shims, Laminated Shims, and Edge Bonded Shims.

SPIROL Application Engineers will review your application needs and work with your design team to recommend the best solution. One way to start the process is to select Shim Applications in our Optimal Application Engineering portal at www. SPIROL.com

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