Why is proper radial clearance important?

When presented with an opportunity to resolve a noise issue, VNC proceeded with a systematic approach in order to determine the root cause and solution.

It all began when elevated noise levels began to be reported in approximately 20% of the customer’s assemblies.

During the initial investigation, the shaft and housings were measured and found to be within tolerance.  Bearing inventories were also measured and individually tested for noise and were found to be good.

Forensic Examination

The forensic examination began by carefully disassembling the bearings. Microscopic investigation of the bearing races yielded evidence of brinelling in about 20% of the inspected bearings.

Brinelling is a material surface failure caused by excessive contact stress. When the contact stress exceeds the material limits, plastic deformation occurs and small indentations can be seen.

In addition to the signs of brinelling, small axial scratches were observed on the raceways at ball spaced intervals. The combination of the axial scratches and brinelling pointed to the failure originating during the installation process.

At this point VNC contacted the customer in order to verify proper installation procedures were being used in the assembly areas. Once the team confirmed that all technicians were using acceptable installation procedures, the focus turned to the suitability of the assembly fits.

The Hypothesis:

Although each of the components were meeting their print specification, the resulting assembly fit, including the statistical variation of each component, must be considered. Even if nominal dimensions yield a desirable assembly fit, the statistical variation of each component must be included in order to consider every possible assembly scenario.

This type of situation, where only a portion of the potential assembly scenarios create undesirable results could explain why only 20% of the customer’s assemblies were exhibiting brinelling.

After detailed calculations, it was determined that brinelling could occur when the shaft was at the high end of the tolerance range and the housing and the bearings were at the low end of the tolerance range.  In this scenario the resulting assembly fit completely removes the radial clearance within the bearing and gives the bearing excessive radial preload. This excessive radial preload correlates to excessive contact stresses which in turn, cause brinelling.

After more calculations, VNC advised that the issue could be resolved up by changing the bearing’s internal radial clearance specification to a “C4” rating.

The Solution:

Working with the customer and their subcontractors, VNC supplied 200 bearings with the new C4 radial clearance specification. These bearings were specifically numbered and special attention was paid to each bearing’s radial clearance and noise measurements.

Before assembly, the other assembly components were also measured, numbered, and tracked. By tracking each component in this manner, the resulting fit of each assembly could be accurately identified and recorded.

Over the next several weeks, the performance of the assemblies was monitored and the results were recorded.  Testing proved that the “C4” radial clearance specification successfully eliminated the brinelling and noise issues seen in the previous assemblies. With the root cause and solution identified, the customer changed their drawings to require the “C4” radial clearance on all bearings for future production.

Contact VNC Bearing today to find out how we can help you.

Benefits Of Using A Cam Follower As Part Of Your Bearing Solution

Cam followers have many benefits and we’re ready to let you in on why you should be using a cam follower as part of your bearing solution. Are you making the most of the bearings that are available to you? If you have heard of a cam follower but have never used one, today we might just change your mind. A cam follower represents a cylindrical roller that is to be attached to a machine component. This component would use a hexagonal nut. Cam follower bearings are used for a number of applications, including linear motion support, locating components during the aforementioned movements, and process transfer lines.

1. One of the pros of using a cam follower bearing is that they always distribute evenly, regardless of the configuration of the unit.

2. They are available for a wide range of linear motions.

3. Cam follower bearings are built thicker than normal bearings, meaning they can absorb more shock than normal and can reduce distortion.

4. They are highly versatile; these bearings are able to fit in whatever solution you desire, whether it’s for a soda machine, aircraft application, or a conveyor line.

At VNC Bearing, we believe there are benefits of using a cam follower as part of your bearing solution. We have a wide selection of cam follower roller bearings and stud type cam follower bearings available for your needs. Visit our extensive catalog online for cam follower bearings, ball bearings, and more. Contact us today with your specific questions, or for more information on cam followers and how you can utilize them in your specific application.