When bearings are 100% inspected with all dimensions on approved drawings based on GB or ISO standard, we confirm bearings are qualified.

Here we would like to share you with a case:

One day we received an urgent request from our customer, that they asked us to deliver one SL bearing (full complement cylindrical roller bearing) to them in short time, reason was that the bearings delivered from their current supplier were rejected by their end user. The problem was the flatness of the end face of outer ring.

End user inspected the flatness of the end face of outer ring by ZEISS Coordinate Measuring Machine, result was 0.14mm, thus bearings were rejected due to too big flatness 0.14mm. All other parameters are qualified based on GB/ISO standard.

For us such problem is the first time to hear, so what is the flatness of the end face of outer ring? See below sketch:

This parameter is generally marked on assembly drawing or not? See below sketch:

We go further to analyze this issue, following facts were found:

1. There is no GB/ISO standard of the parameter “flatness of end face of outer ring” for any kinds of bearings, so on assembly drawing it doesn’t exist
2. There’s no GB/ISO standard to clarify inspection method of the parameter “flatness of end face of outer ring” for any kind of bearings

So how producers control and guarantee this parameter?

For this reason, we discussed with many Chinese bearing producers, and in the view of Chinese bearing producers, this parameter is very easy to be controlled by high precision processing machines during production, generally it’s not possible to reach 0.14mm, although they also never inspect this parameter before as they don’t know how to inspect it. In China most bearing producers don’t have Coordinate Measuring machine.

So how this issue happened?

What we should do to avoid it in advance?

Do you know?