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Very cheap Hardness Blocks unfortunately without Traceability


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We are an ISO 17025 Nata laboratory and all our hardness blocks are supplied by an NVLAP Accredited laboratories..
The most used blocks are currently running out of space for indentations and just found out a company in China ( ISO 9001 certified ) that makes several hardness tester and standardized blocks as well for more than 50 years...

Because they were cheap, I did give it a go and buy some blocks with them but unfortunately they did not supply me any papers with it.
Just a paper in chinese character stating the mean Hardness and which scale..
They were honest to tell me that they are not a ISO 17025 laboratory and they are just manufacturer ( ISO 9001 ) certified.

I've checked the blocks at my end in reference to ISO 6508.3 and its within the acceptable hardness and uniformity.

It's a shame that we cannot use them because they are not traceable especially if they 200% cheaper...LOL
The calibration on these blocks does not meet the requirements of 17025

A calibration laboratory establishes traceability of its own measurement standards and measuring instruments to the SI by means of an unbroken chain of calibrations or comparisons linking them to relevant primary standards of the SI units of measurement. The link to SI units may be achieved by reference to national measurement standards. National measurement standards may be primary standards, which are primary realizations of the SI units or agreed representations of SI units based on fundamental physical constants, or they may be secondary standards which are standards calibrated by another national metrology institute.
When using external calibration services, traceability of measurement shall be assured by the use of calibration services from laboratories that can demonstrate competence, measurement capability and traceability.
The calibration certificates issued by these laboratories shall contain the measurement results, including the measurement uncertainty and/or a statement of compliance with an identified metrological specification (see also

The certificate that you have for your blocks does not meet the requirement of issuing a certificate "shall contain the measurement results, including the measurement uncertainty and/or a statement of compliance with an identified metrological specification". Without measurement uncertainty and a statement of traceability you have nothing to justify the traceability of your measurements. You are going to have to send these new blocks out to a 17025 accredited lab and get a 17025 accredited calibration in order to meet requirements.
Something else that I thought of.

Since you are a 17025 accredited laboratory you will also need to check with your accrediting body to see if they have additional specific traceability requirements.

The AB I work through requires that the lab used be from a mutually recognized body, that a logo for the accredited calibration be on the certificate, etc. They have a measurement traceability document that spells out all of the details.


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Thanks dwperron for your reply.
Just want to be cleared that we are a Testing Lab and not a Calib Lab.
Actually my intention is to use the blocks for periodical testing ( daily checks ) of Rockwell and Brinell tester.
My plan is to use our NVLAP blocks for our bi annual indirect verification and just use the chinese blocks for day to day periodicals..
Thanks for the clarification.

If you are using the NVLAP blocks for the calibration (bi annual indirect verification) of your testers then you would be fine, you have maintained traceability. Using the chinese blocks for daily QC checks sounds like a good idea.


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got an email back from my chinese supplier"
It seems they really want our business.
Would this be enough?

As I mentioned our company is the only hardness delivery enterprise in China which is authorized by AQSIQ (Administration of Quality Supervision Inspection and Quarantine of China).". Our standard hardness testing machines are calibrated termly by government according to our National Standards which also conforms to ISO and ASTM.
I do not see how this would work.

Since they are not a 17025 accredited organization providing you with an accredited calibration it would require that you be able to demonstrate traceability of their calibrations, including measurement uncertainties, all the way back to their National Standards body - this can be exceedingly hard to get all of that information, as you would need it for all of the equipment and the standards that were used on all calibrations involved going back to their National Standards body.

You would then have to get your accreditation body and their assessors to approve your measurement traceability. Like I said before, accreditation bodies have their own rules as to what they will require to confirm measurement traceability, you need to contact your accreditation body to see their requirements. Most require that you use accredited laboratories if they are available.

It will definitely be easier to send your blocks to a 17025 accredited lab for calibration. When you factor in the time you spend trying to prove traceability yourself it is probably also the cheaper solution.


The labs used in China wont be able to do the job. They need to have machines that are classified as "Standardizing" by ASTM E-18 for Rockwell scales. Tolerances for these machines are much tighter than regular machines. Most labs there follow the local standard, which does not match ASTM standards, even though, they might reference such. Best way is to just use them for daily general purpose reference. Use real NIST certified blocks for necessary traceability purposes. The combined overall costs are not worth taking unnecessary chances for.
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