One of my favourite reference book titles, because of the obvious humorous aspect to it, is Doubt-Free Uncertainty in Measurement*.
It seems to me that one of the big difficulties surrounding the uptake of measurement uncertainty in metal hardness testing is the off-putting language – we should really talk about certainty instead.
To some extent, uncertainty is what people actually mean when they talk about “tolerances”. One key difference, however, is that a tolerance requires a datum, whereas uncertainty is an expression of confidence in the accuracy of a result.
Historically, people have talked about tolerances and built them into their specifications to give a margin of protection – regardless of which type of measurements those tolerances relate to. For example, people might say a dimension needs to be +/- 0.5 mm or a hardness value needs to be +/- 2 HBW points etc. The difficulty with this approach is that it requires an absolutely perfect measuring instrument otherwise how do you know the value of your nominal datum? What you are really saying is that “if the result is within this margin then my risk of being wrong is small enough to be acceptable”.
This is where uncertainty comes in and short-cuts the process.
By using uncertainty instead of tolerance one can say (for example) that a result is 300 HBW with a confidence value of 99.9% etc.
If you are able to tell your customers that your results have a 99.9% probability of being right and your competitors can only say they are 95% confident in their results then you automatically have an unassailable competitive advantage.
At Foundrax we’ve worked very hard to achieve the best calibration and measurement capabilities and as a result our schedule of accreditation shows that, for our Brinell reference blocks, our capability is amongst the best in the game. By default, therefore, our confidence in our results is very high (ie our uncertainty of measurement is very low).
What this means for the user is simple: If you use our reference blocks to check your machines and microscopes then you can do so with very high confidence in your results and, should you have a dispute with a customer or a supplier, it places you in an authoritative position.
Our blocks are directly traceable to PTB in Germany, our master calibration machine was built (and is maintained) by us and is good enough to be accepted as a National Standard Brinell Calibration unit, were that ever to be required. The steel is rolled to our specifications, we lap and polish in-house and we laser etch a grid onto each block to give maximum lifespan and ease of use.
If you’d like to find out more, please get in touch.
*Ratcliffe, C. and Ratcliffe, R., Springer, 2015