Rockwell hardness test

The Rockwell hardness test can be divided into two groups: Rockwell and Superficial Rockwell. The difference is given by the test loads, which for the Rockwell test are heavier than for the Superficial Rockwell test.

The ERNST Rockwell hardness testers are designed to take the advantages from the Rockwell test, such as the employ of diamond indenters for testing tempered steel or hard metals, and the ball penetrators for soft metals. The Rockwell method allows testing of plastic even under load.

The ERNST Rockwell hardness testers allow overcoming some limitations of the Rockwell method. The main disadvantage of the traditional Rockwell hardness testers is that the accuracy of testing depends to a large degree on the perfect contact between the work piece and its support, usually called the anvil.

In the presence of oil coat, some grease or other between the test part and the anvil, a little movement occurs during load application, when added to the indentation depth, gives a wrong result, decreasing the hardness value. Because it is not always possible to work in perfect conditions, for example in heat treatment or workshop environments, this is an important consideration.

To overcome this problem, almost our hardness testers (AT-series, TWIN, BRE-AUT, COMPUTEST SC, DYNATEST SC) work according to a modification to the Rockwell principle. In this case, a support on the test surface gives the penetration depth. Therefore, any movement of the part, elevating screw or stand, does not influence the test result. Thanks to this method, the same advantages of the Brinell and Vickers principle are reached.

The ERNST bench hardness testers have a third important component, called clamping shield. The clamping shield is used for locking of the test piece, avoiding the use of any special support; the clamping shield can be easily removed if needed. In portable hardness testers, this component is called base, it is interchangeable and helps creating a perfect support on the test piece.