ASTM E18-07 Rockwell Hardness Standard

The long awaited ASTM E18 has been released. While it is technically very similar to the older version, some changes affect you as a user, and us, as a service provider.

Here is a brief summary of the major changes:

INDENTERS

All indenters require certifications and serial numbers. In the case of diamond indenters, there are now three classes, each class having different tolerances.

Class B diamond indenters are intended for everyday use.
Class A indenters are used for standardizing Class B indenters during the manufacturing process, and for troubleshooting by service technicians.
Reference diamonds are used to standardize Class A Diamonds.

In the past, to comply with E18, diamonds were required to have their shape verified on an optical comparator, and then undergo performance verification on test blocks. E18-07 now requires that each indenter have it’s geometrical attributes (angle and radius) physically measured to insure compliance. This eliminates the “go/no go” measurements allowed by the old standard.

What this means to you is that unless you have a certification for a given diamond that states that it was physically measured and is compliant with the tolerances for geometry and performance outlined in E18-07, your machine cannot be certified to ASTM E-18-07. Unfortunately, most diamond manufacturers are not currently in a position to ship these diamonds. In the case of our diamond vendor, UKAS (an accreditation agency) needs to approve the modification of their certifications before they can begin to do so. We expect to have this resolved, and be capable of shipping E-18-07 diamonds in about four weeks.

Ball indenters will also require a certification, demonstrating that the indenter was performance verified, and that there is at least 0.3 mm protrusion of the ball from the ball cap. (Newage technicians are capable of performing this verification for you.)

The new standard also ties an indenter to a machine. This means that an indenter must be verified (and abbreviated indirect verification) and tied by serial number to a given machine, before it can be used to measure parts. The indenter must be verified on two test blocks for each scale that it is intended to be used on. (ie HRA, HRC, HR15N) A certificate must be generated and kept similar to the ones generated when your machine is certified.

Users are allowed to perform this verification themselves, or Newage can perform this service for you. There will be a $50.00 charge per indenter to perform this service on indenters that are certified to meet E18-07

DIRECT VERIFICATIONS

Direct verifications are a means of inspecting individual critical attributes of a hardness tester. In a Rockwell hardness tester that includes measuring the force at preload, total force, and force at elastic recovery (the reading position). The displacement measuring device must be isolated and verified. Additionally, the timing, and machine hysteresis must be verified.

Direct verifications have always been done by testing machine manufacturers when machines are manufactured. They were also performed when machines are rebuilt, and as a diagnostic tool when the force, or measuring systems are suspect. The new standard now states an Direct Verification (less the timing) must be performed “When adjustments, modifications, or repairs are made that could affect the application of test forces, the depth measuring system, or the machine hysteresis.”

To comply with this E18-07, if adjustments are made that affect any of these key elements, service technicians can no longer just rely on performance of the machine on test blocks. A direct verification must be done to insure that all of these elements are in tolerance, and are not simply correct by “canceling errors”.

In other words, there may be cases where an instrument reads the test blocks within tolerance, but fails a direct verification. Under the new revision, these machines cannot be deemed “Certifiable” unless the machine can be adjusted/repaired to pass both a direct and an indirect verification.

AS FOUND RESULTS

The old revision of E18 was rather ambiguous regarding service technicians reporting as found results. E-18-07 now states that as found results must be obtained and recorded for every scale that is to be recertified. Historically, As Founds were taken on the scale on which the machine was “as found”. This is a time consuming process, not to mention the additional test block consumption, which will force Newage to adjust our service pricing.

WHAT CAN YOU DO IN THE INTERIM?

If you are not prepared to meet the new revision of E –18, our service technicians can certify your instruments in accordance with ASTM E18-05, which is the previous version.

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