When you say single plane diameter deviation, my thoughts are that when you establish a cylinder, you need several diameter measurements taken at different heights to establish an average used to construct the cylinder. A single plane diameter deviation is the amount of deviation you might expect in any single circular measurement.

Can you provide more detail and maybe we can be more exact.

Hi,

"report about chamfer dimension (which seems to have great impact on the bearing quality)"

not the chamfer is critical but any protruding parts that may be originating from deformations or unadequate deburring during manufacturing or handling.

These form high spots that will first contact the shaft or the bore and thus deforme the bearing rings and thus the raceway.

Have in mind that inadequate mounting is one of the major causes for bearing failure.

Regardless where the kinks are in the mating surfaces they will give rise to deformations.

"Master" is a piece of bearing material or ceramics that is machined to better geometry than any quality you want to produce.

Is required in calibrating measurement devices or directly do the difference between produced piece and master-piece.

Many more supporting comments available on request.

RHABE

SMB Bearing Tolerances

According to ISO & AFBMA specifications

Do you understand bearing tolerances and what they really mean? If not, you're not alone. These are often quoted but often without any real understanding of what they mean. Websites with simple explanations of bearing tolerances are extremely rare so we decided to fill the gap. Many thanks to EZO in Japan for their help. So, if you want to know what "Mean Bore Deviation" and "Single Bore Variation" actually mean? Read on as we hope to make this much clearer.

Deviation This dictates how far away from the nominal dimension, the actual measurement is allowed to be. The nominal dimension is the one shown in the manufacturer's catalogue e.g. 6200 has a nominal bore of 10mm, 688 has a nominal bore of 8mm etc. Limits on the maximum deviation from these dimensions are extremely important. Without international tolerance standards for bearings (ISO and AFBMA), it would be up to each individual manufacturer. This could mean you order a 688 bearing (8mm bore) only to find that it is 7mm bore and won't fit the shaft. Deviation tolerances usually allow the bore or OD to be smaller but no bigger than the nominal dimension.

Mean Bore/OD Deviation
... or single plane mean bore diameter deviation. This is an important tolerance when looking to closely mate inner ring and shaft or outer ring and housing. First you need to understand that a bearing is not round. Of course its not far off but when you start measuring in microns (thousandths of a millimetre) you realise the measurements vary. Lets take the bore of a 688 bearing (8 x 16 x 5mm) as an example. Depending on where in the inner ring you take your measurement, you may get a reading of anywhere, say, between 8mm and 7.991 mm so what do you take as the bore size? This is where Mean Deviation comes in. This involves taking a number of measurements in a single radial plane (we'll come to that in a minute) across the bore or OD to average out the diameter of that ring..

This drawing represents an inner or outer bearing ring. The arrows represent various measurements taken across the bore or OD in different directions to help discover the mean size. This set of measurements have correctly been taken in a single radial plane i.e. at the same point along the length of the bore or OD. Sets of measurements should also be taken in different radial planes to make sure the bore/OD is within tolerances along its length.



This diagram shows how NOT to do it. Each measurement has been taken at a different point along the length of the bearing ring, in other words, each measurement has been taken in a different radial plane (tut, tut).

This is an end view of the bearing inner ring. You will see that we now show the different measurements taken in the same radial plane. To calculate the mean bore size, we add the largest measurement to the smallest measurement and divide by 2. In this case, 8.000 plus 7.994 divided by 2 = 7.997

So in this case the mean bore size is 7.997mm which is far more useful when calculating the shaft tolerance than a single bore measurement which might be misleading. The nominal bore of a 688ZZ is 8mm, the mean bore size here is 7.997mm so the mean bore deviation for this bearing is -0.003mm. The mean bore deviation tolerance for a P0 bearing of this size is +0/-0.008mm. This means that the mean bore can be between 7.992mm and 8.000mm. The same principle applies to the outer ring.

I hope this helps. It helped me.

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