Different Bearing Swaging Methods

Installing your bearings using anvil staking seems like an ideal option on the surface; one process is used to stake both sides of the bearing, the pressure applied is controllable, and the tools are comparatively cheaper. However, the excessive force required for installation can be detrimental to the bearing and getting a consistent finish can prove surprisingly challenging.

A bearing with a 1.500in outer diameter requires around 18,000 lbs force to anvil stake into an assembly according to data collected by NMB Minembia. We have seen this amount of force has the potential to damage the PTFE linear. When combined with a stack-up of housing tolerances, the breakaway torque or misalignment torque can be impacted to yield an increased or inconsistent bearing friction. Moreover, when applying this much pressure, the size of the press can be cumbersome in a workshop. In combination, many customers find anvil staking bearings to be either impossible or unnecessarily dangerous for many MRO shops.

One of the most common issues we see is what is called "spring back". This occurs almost exclusively with anvil staking bearings which is when there is incomplete contact between the bearing v-groove and housing chamfer. The lifting of this annual lip can lead to a quality failure as the material is not properly affixed to the housing.

The next logical step in the tool progression is the two-wheel swaging tool, which can be modified for use with different bearing sizes with relative ease. This tool eliminates the need for excessive force and can be used in both hand-held situations and in a commonly available vertical milling machine. However, a significant design flaw means that disadvantages can quickly become apparent.

The geometry of the rollers do not necessarily combine well with the assembly design of the tool, meaning that the tool and the rollers rotate at different speeds. This then generates significant friction on the bearing v-groove which could lead to galling. This means that the bearing surface finish is deteriorated, drastically increasing the assembly failure rate.

This style of tool often comes in a kit compatible with a large bearing range; each component is manufactured to relatively loose tolerances, meaning that the operator is responsible for the tool performance and assembly. An incorrect washer will produce the wrong swage diameter and cause irreparable damage to the bearing. Components can also very easily be misplaced, turning a standard job into a sourcing nightmare. This is where the tri-roller swaging method saves the day.

Upon its introduction to the market, the tri-roller swaging tool has revolutionised the bearing installation process. The three-roller design, set at 120°, optimises the rolling friction and accurately forms the v-groove onto the housing chamfer.

Advantages

• Precision engineered tool to suit each bearing ensures perfect conformity, every time
• Uniform and consistent forming around bearing circumference
• Repeatable process with minimal user proficiency required
• Mirror surface finish on bearing
• Low operating pressure required
• Available in portable style
• Acceptable method by all leading aircraft manufacturers
• Requires only one operator while portable anvil staking tools can be incredibly heavy
• Custom designs to suit challenging geometries
• Quick return of investment

 Disadvantages

• Higher initial cost
• More space required for tool clearance
• More time consuming than anvil staking but faster than two-wheel swaging

A simple, controllable process, with completely hand-held methods available, bearing assemblies using tri-roller swaging consistently pass inspection. Although there is an initial cost increase, this is easily eradicated by the elimination of rejected parts. The massively increased pass rate also reduces the overall production time, despite the initial process being lengthier than anvil staking. UNASIS engineering advancements have also supplemented the increased space requirements.

When used correctly, the tri-roller swaging method will complete the job correctly every time, proving with certainty that the tool has been precision engineered for complete peace of mind.

To conclude, UNASIS is the premium brand for tri-roller swaging, the optimum process for bearing installation. With on-call engineers and a warehouse full of tools, we are perfectly equipped to help you take on your job. We can also manufacture anvil and two-wheel style tools upon request, so please get in touch with any technical questions or requirements regarding bearing installation, removal, or testing.