CONCENTRICITY ON CMM - THE SOLUTION

Concentricity measurement is the biggest challenge in the industry measuring either on CMM or by conventional measurement.
Repeatability, Reproduceability and correlation of measurement is always a question mark when inspection is done with regular inspection method.
This video demonstrates the measurement of concentricity with new approach, based on the international research studies and the best industry practices.
All the references link are given to learners in this video so they can further study.

[@sajalbanik6066]

Thank you sir for sharing your excellent explanation (specially rule of proportionality and coaxiality tolerance challenges) in such way with practical and animation approach. Please keep sharing .

[@stevegyro1]

Magnificent, with good illustrations and live video with indicators! By knowing the sequence of operations performed on this part, preceding this measurement, helps in the understanding.
This video is so powerful bc it underlies many of the mistakes made by programmers who are good programmers, but do not always understand the ‘leverage’ effects, measuring a small surface (in relation to rest of the part) and using that plane or cylinder as Spacial/primary datum.

[@accurateasmeiso4262]

Thanks i

[@mcdoogle274]

There are some fundemental mistakes here:
1. You have to understand the difference between concentricity and coaxiality. Both use the same symbol, but in ISO, the symbol usually means coaxiality and it requires the evaluation of the whole length of an axis. But in ASME standards before Y14.5-2018, there was ONLY concentricity, which was mathematically measured DIFFERENTLY from the coaxiality in ISO (see point 2).
2. In ASME, concentricity used to be measured only within a plane section of a cylinder. The section did not need to be a circle, it could be any shape, but there had to be opposing points within the shape. For every set of opposing points, there had to be calculated a mid-point. The set of all mid-points had to be within the tolerance zone of the datum. This had to be true for every section of the evaluated feature. This method sometimes yielded different results than the ISO method. It is very complicated to realize this measurement on a CMM, because it involves a lot of calculation, and I know of NO software that was able to do this out of the box.
3. BUT: In ASME Y14.5-2018, the concentricity was REMOVED from the standard. It doesn't exist anymore, and the use of the symbol is NOT ALLOWED ANYMORE. Instead, you have to use the position tolerance in a similar way as the coaxiality in the ISO standard, which does still exist and uses the same symbol, which could be a little confusing.
4. There are rumours, that even in ISO, within the next few years, the coaxiality symbol could be removed as well, since there had been the mentioned differences in the use between ISO and ASME, and concentricity/coaxiality had been a constant reason for misunderstandings within and among the different standards.

[@shrinivasdeshpande9705]

How to take common datum on cmm. I am using Accurate spectra.

[@accurateasmeiso4262]

Measure bothe the datum features. If both are circles construct a line. Make this line a datum.
It is common datum.