In the first half of 2007 ASTM Subcommittee E28.06 passed new versions of E18 for Rockwell testing. These new documents took several years to finish and are complete rewrites of the popular test method. There are many technical changes and new document requirements that can have a far reaching effect, especially when you have to satisfy the needs of an auditor. It may be that none of your Rockwell test results meet the new standards.
Rockwell Test Blocks:
E18-07 and later test methods require that Rockwell Test Blocks be calibrated with Class A indenters. Diamond scale class A indenters are required to be calibrated against a reference indenter traceable to National Standards (i.e. NIST, NPL, PTB or equivalent etc.). Ball scale indenters are now required to be performance, geometry, hardness, density and chemical analysis verified which previous to this change did not include performance verification. The impact of these changes now make test blocks calibrated by a diamond directly traceable to National Standards. This is a huge step forward in unifying hardness levels between all hardness manufacturers in the United States.
Previous to this change all hardness manufacturers maintained their own hardness levels for these scales which in some cases caused large differences in hardness levels between manufacturers. Also the traceability of these blocks were limited to be traceable to the manufacturer's own hardness levels. Now that diamond scale test blocks are directly traceable to NIST the manufacturer had to adjust their hardness levels to match NIST or another recognized National Standard. This has a trickle down affect down to the everday users by making the newer test blocks read differently from test blocks previously calibrated to E18-07. These changes have made test blocks calibrated to pre E18-07 obsolete and in order to be compliant with the new standard either new E18-07 or later test blocks need to be obtained or older non-compliant test blocks can be recalibrated.
Rockwell Testers:
With the latest E18 changes to test blocks and indenters your Rockwell tester will need to be re-verified to E18-07 or later to ensure compliant test results.