x

Blog

Hardness Testing Products

Rockwell Hardness Testers

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  

Hardness of the Material

Why is it important to know? Knowing the hardness of the material you are machining is important.  It helps determine the appropriate speeds and feeds for your application and can affect the design of the tool being used in the machining process.  Despite this importance, it is surprising, although very common, that many machinists do not know the hardness of the material they are working with.  This can lead to any number of adverse machining results such as poor finish, reduced tool life, tool breakage, and even scrapping out the part you are working on. In our industry, hardness is typically measured in Rockwell (HRc) or Brinell and can be obtained by using a hardness tester; a fairly common device found in many machine shops.  The tester consists of a diamond tipped indenter that is pressed into the material with a given amount of force.  The deeper it goes, the softer the material.  The hardness could also be obtained from the vendor that provided the material provided no other processes, such as heat treating, were performed on the material. Every week I quote a lot of specials tools.  Sometimes I know the material that is going to be machined and sometimes I do not.  Of the times I do know the material seldom does the customer provide the hardness.  This is an important variable to know and can drastically effect the design of the tool and the way that we would recommend the tool be ran.   If I have the opportunity to get more information from the customer, one of my questions is always “What is the hardness?” All too often, the customer cannot provide an answer, so I’m forced to guess.  If you want your tool to perform optimally it is worth the extra time to figure it out. As an example of how widely the speeds and feeds can vary based on the hardness within the same type of material, take a look at our Milling Cutter speeds and feeds chart (http://www.supertoolinc.com/uploads/MillingFeedsandSpeeds.pdf).  Scroll down to the “Medium Strength Steels” Class of Material, specifically the Stainless Steel 400 series.  The Brinell hardness can range from 135-325.  At 135 Brinell the recommended starting Surface Feet Per Minute is 400 which for a 3” diameter milling cutter works out to 509.3 RPM’s.  At 325 Brinell the recommended starting Surface Feet Per Minute is 200 which for a 3” diameter milling cutter works out to 254.7 RPM’s. .  509.3 RPM’s versus 254.7 RPM’s.  That is twice as many RPM’s cutting the same material with different hardnesses!  You can see why knowing the hardness is important.  It is not just important in milling; it is important in all machining applications including reaming, drilling, counterboring, turning, etc.  

Rockwell, Brinell, and Vickers Metal Hardness Tests: What’s the Difference?

Completing a hardness test is a critical step in qualifying metal parts; these tests determine the various properties of a specific metal, such as resistance to wear, toughness, and formability. Different test scales were created to assist engineers in selecting the appropriate metals and hardness for their specific application.To help you understand the different test scales we’ve created a cross-reference table for three of the most popular hardness tests below.   Brinell Hardness Test The first widely used standardized hardness test, the Brinell method determines the indentation hardness of metal materials and is typically used for materials with a coarse surface or a surface too rough to be tested through other methods. The Brinell test is not useful for fully hardened steel or other hard materials, however, and often leaves a large impression on the metal. The Brinell test is also very slow. Rockwell Hardness Test Developed to provide a less destructive alternative to the Brinell test, this differential-depth method eliminates the errors associated with mechanical imperfections. Quicker and cheaper than the Brinell and Vickers tests, the Rockwell test requires no material prep, and hardness value is easily readable without any extra equipment, making this one of the most commonly used methods of measuring metal hardness. Vickers Hardness Test Making use of a diamond indenter, the Vickers hardness test is done with less force and more accuracy than the Brinell test. By magnifying the surface of a metal, this test can target specific microstructural constituents like martensite or bainite, or assess the quality of heat treating or surface hardening operations. Requiring an optical system and material prep, the Vickers test incurs higher costs and takes longer to complete than the Rockwell test. Selecting the Right Hardness Test for Your Application To assist you in understanding the most popular test scales, ESI has created a free Hardness Conversion Table, with approximate tensile strength in PSI and MPa as well as groupings of approximate fastener property classes compiled in one easy-to-read guide. Written by Ron Delfini on June 14, 2017 https://www.esict.com/blog/rockwell-brinell-and-vickers-metal-hardness

How to Choose the Right Hardness Tester

Kind of Hardness Tester There are two main types of hardness testing tool – bench (stationary, classical) and portable (mobile, electronic). Bench hardness tester – is the classical hardness tester which measures hardness by standard methods Brinell or Rockwell or Vickery or Shor and so on. As a rule, hardness tester name, including the title of the hardness scale. As an example, “Rockwell Bench hardness tester” and “Bench Brinell hardness tester”. There is some bench top hardness tester that allows the user to measure hardness not only by the scale, but also by the several large hardness scale. For example, there is a bench hardness tester that allows the user to measure hardness with Rockwell, Brinell and Vickers scale. All Bench hardness testers are large and heavy (over 50 kg), these units also must be mounted on a table or on the floor. The main advantage of such devices – is the implementation of the classical model, the direct method of measuring the hardness. Portable Leeb hardness tester Portable hardness tester – as opposed to bench hardness tester, this instrument has a small size, light weight, and they are compact devices that measure hardness with some scale violence. Typically, modern portable hardness testers can measure the hardness of all scale violence. Advantages of portable hardness testers is to enable users to take the device and with it to measure samples. You do not need to take the sample into the workshop. Bench Hardness Tester Portable hardness measuring instrument – is an electronic device, so they usually have a set of useful features-users can save the measurement results in internal storage, after which the results can be sent to a computer to create reports in a special program ARM control, which is provided with a portable hardness testers, portable hardness testers – in contrast to bench hardness testers, it has some advantages, but there are some cases, when they can be solved only by a bench hardness tester. However, such cases are very rare, and we can say that in 99 cases out of 100, the user can use the portable device. As a rule, the most useful and easy to carry is a portable device. That is why it is the best solution.  

Measuring Indentation Hardness

Anyone can notice that a rock is harder than a plastic toy. But when you work in engineering or metallurgy, measuring hardness becomes much more complex. There are several ways to measure the hardness of a material. In the engineering and metallurgy fields, workers most often measure the indentation hardness. Indentation hardness measures how resistant a material is to changing when it is compressed. To measure indentation hardness, workers use equipment to compress the material. They then measure the level of indentation left behind on the material. Generally speaking, a smaller indentation indicates a harder material. The way to measure indentation hardness differs depending on the scale you use. Comparing Hardness Scales When measuring indentation harness, there are four possible scales to choose from. The type of scale you use affects which type of equipment you use. Brinell Scale Invented in 1900 by Johan August Brinell, the Brinell scale was the first hardness scale used by engineers and metal workers. To perform a Brinell test, an indenter penetrates the desired material. People prefer the Brinell scale if they also need to determine the ultimate tensile strength (UTS) of steel. That's because when you divide the Brinell scale hardness value in half, you get the UTS in pounds per square inch. Rockwell Scale The Rockwell scale was invented in the early 1900s by Hugh and Stanley Rockwell. This scale compares the indentation caused by a large load with the indentation caused by a smaller load. The Rockwell test preserves a material's integrity better than the Brinell test does. The Brinell test leaves a large impression that can actually damage the material being tested. Vickers Scale The Vickers scale was invented in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd. The hardness measurements on the Vickers test are often easier to determine than measurements with other scales. Unlike with other tests, the size of the Vickers indenter doesn't affect the hardness calculations. Shore Scale Invented by Albert Ferdinand Shore in the 1920s, the shore hardness scale uses a device called a durometer. Like other hardness equipment, the durometer applies force to the material and measures the depth of the indentation. Unlike the other hardness scales, which focus on metals, the shore scale measures the hardness of elastomers, rubbers, and polymers. Comparing Tester Equipment Each type of hardness scale requires different types of equipment. Rockwell and Brinell testing rely on two main kinds of equipment: bench and portable. Bench equipment sits on top of a work bench. It displays the test results either on a dial (analog models) or on a digital screen (digital models). Portable equipment differs because, along with being portable, it can test larger metal than bench equipment can. A Vickers hardness tester is unique because it uses a diamond as the indenter. Diamonds create the same shaped impressions, regardless of the material they are measuring. Plus, since diamonds create relatively small indentations, Vickers equipment is ideal for testing thin materials like foil. As mentioned, a durometer is the instrument used for shore scale testing. A durometer is a test stand that resembles a kitchen scale. There are several different durometer styles, including classic style, pencil style, and ergo style. Each is built to meet certain specifications. For example, pencil-style durometers have a tiny base, which enables them to measure areas that are difficult to reach. When it comes to measuring indentation hardness, you have many options to choose from. If you're looking for the right equipment to test the hardness of your materials, count on us at WESTport Corporation. We offer a variety of hardness testing equipment to meet your project requirements.  

Blog