How they are used and which model type is best for you?
The Rockwell Hardness Scale is used to rank the hardness of materials, and it is widely used in the fields of metallurgy and engineering. The Rockwell test uses indentation to test the hardness of a material. Each different Rockwell scale uses a different indenter and load weight to test the material. The results of the test are given a code that includes HR and then the scale letter, i.e. HRA or HRB.
To evaluate hardness, Rockwell hardness testers use a differential-depth method. The test consists of placing an indenter on the material, then applying a minor load, which establishes the zero position. After the minor load, a major load is applied and then removed while the minor load is maintained. The difference in depth between the minor and major loads determines the hardness. A dial or display shows the depth of penetration, and a higher number equals a harder material. Rockwell hardness testers are particularly useful because of their simplicity; they eliminate the extensive calculations used by other methods. The Rockwell test is also popular because of its reliability of results and the very small indentation to the material.
Generally, material to be tested should be at least ten times the depth of the indentation, but if very thin or brittle materials need to be tested, a superficial Rockwell scale is used. It makes a much shallower indentation and uses a lower load to avoid damaging materials like ceramics and sheet metal.
Rockwell Hardness Testers vary for different uses, but they fall into one of three basic categories:
- Bench models. Often found in testing laboratories and workshops, these testers are built to sit atop a work bench and test sample blocks. Bench models come in two types:
- Analog models display the test result through a dial on the front of the machine. They are simple and easy to use and very accurate.
- Digital models display the test result on a screen. They often have multiple functionalities for various tests, so they are versatile, but require more training to operate.
- Portable models. These testers are generally used to test very large metal parts (at least 1” thick). They use a digital screen, and can be programed to test using multiple hardness scales. By far the most economic choice for a hardness tester, WESTport Corporation recommends the Phase ll portable hardness tester.
In doing side by side studies of portable hardness testers we have found that the Phase ll PHT-3500 Portable Hardness Tester is an excellent choice. It provides an excellent quality machine while providing substantial savings over competing models. It comes with advanced USB output and thermal printing capabilities. It’s loaded with useful functions and even a mini printer. You can use the simple keypad to choose from a variety of tests that easily convert to popular hardness scales like Rockwell, Brinell, Vickers, and Shore. There is also no need to bother looking up a conversion chart; the Phase ll PHT-3500 automatically converts to your scale of choice. Accuracy is assured with a backlit LCD display that ensures readability in all conditions. The large display screen also shows the mean value and the Min and Max values, plus the battery level.
The Phase ll PHT-3500 comes complete with the hardness tester, impact device D, a calibrated test block, a custom carry case, operation manual, and a cleaning brush all for a great price. Click here for more details and to get a price quote.
Whether you choose a bench model or a portable hardness tester, all Rockwell hardness testers need to be calibrated with standard Rockwell test blocks. Rockwell test blocks are pieces of steel, brass, or aluminum that have been specially heat treated and calibrated for consistency. By using a test block, Rockwell hardness testers can be calibrated for optimal precision. All of WESTport Corporation’s test blocks are calibrated to ASTM E18, ANSI (NCSL) Z540-1, (ISO) 10012-1, ISO/IEC 17025, and ISO 6508, and they are certified in our ISO/IEC 17025 accredited laboratory. Each test block is hand lapped and diamond polished to a mirror finish, and they include a lifetime guarantee.
Whatever your hardness testing needs are, the WESTport team is here to provide you with complete free technical support and with “Quality you can Trust” servicing industry since 1989.
Written by Kate Hansen, Edited by Robert Forbes – WESTport Corporation – January 28, 2015
