King highlights test block considerations in hardness testing
August 27, 2018
King Tester Corporation, headquartered in Phoenixville, Pennsylvania, USA, is a leading manufacturer and distributor of Brinell and Rockwell testers, supplying customers in aerospace, defense, manufacturing, oil and gas, and heat treating industries. A recent article posted on the company’s website highlights the importance of choosing the right test block when performing hardness testing, and identifies the factors to consider in making the correct choice.
It is stated that many people operate under a misconception they must use a test block equivalent in hardness to the parts or samples they are testing. However, King claim this is not the case. While it is wise to choose a test block within a reasonable range of the same hardness you do not need to match the hardness exactly, it is stated.
The Test Block is used to indirectly verify the force being applied by the tester is equivalent to the calibrated force of the tester. This is done by using the tester to apply force to a known metal hardness (the Test Block). The result is then compared to the master indentations on the Test Block to determine if the Tester is applying accurate pressure.
The article discusses a number of key factors to consider. King states that the Test Block should be within a reasonable range of the hardness of the material to be tested, but it does not need to be exact. The company recommends a test block +/- 50 HBW from the parts target hardness. Conformance with ASTM standards is also said to be an important factor. This means the test Block has a limited number of indentation opportunities and may only use the designated test surface, as specified in ASTM E10
King Tester offers ASTM E10 and ISO-17025 certified test blocks in both 2×6 and 4×4 sizes in a wide range of hardnesses. A patented alphanumeric grid system allows users to log and track daily verifications.