HR = Rockwell hardness value N = total load applied to the indenter d = depth of penetration of the indenter D = diameter of the indenter
Where HR is the Rockwell hardness value, N is the load applied (in kgf), d is the depth of the indentation (in mm), and D is the diameter of the ball or the width of the diamond cone (in mm). The Rockwell hardness test uses different scales based on the load applied and the type of indenter used. The most common scales are the A, B, C, D, E, F, G, and H scales, each with a different combination of load and indenter. The Rockwell hardness test is widely used to measure the hardness of materials, including metals, plastics, and ceramics.
To apply the formula for Rockwell hardness, you will need to have the following information:
The load applied (in kgf)
The depth of the indentation (in mm)
The diameter of the ball or the width of the diamond cone (in mm)
Once you have this information, you can use the following steps to calculate the Rockwell hardness value:
Determine the Rockwell scale: The Rockwell scale is determined by the load applied and the type of indenter used. For example, the Rockwell C scale uses a 150 kgf load and a diamond cone indenter.
Measure the depth of the indentation: Use a microscope or other measuring device to measure the depth of the indentation made by the indenter.
Calculate the Rockwell hardness value: Use the following formula to calculate the Rockwell hardness value:HR = N – (d / D)where HR is the Rockwell hardness value, N is the load applied (in kgf), d is the depth of the indentation (in mm), and D is the diameter of the ball or the width of the diamond cone (in mm).
Interpret the results: The Rockwell hardness value can be compared to a standard chart to determine the hardness of the material being tested.
It is important to note that the Rockwell hardness test should be performed by a qualified technician using properly calibrated equipment. The test results may be affected by factors such as the surface finish of the material and the accuracy of the measuring equipment.
The Rockwell hardness test is one of the most widely used hardness tests in the United States. This is because it is relatively simple to perform, provides a quick and accurate measurement of hardness, and can be used to measure the hardness of a wide variety of materials, including metals, plastics, and ceramics. The Rockwell hardness test is also standardized by ASTM International, which provides guidelines for performing the test and interpreting the results.
The accuracy of portable hardness testers depends on several factors, such as the tester you are using, the material you are testing, the condition of the surface, and your skill and experience. In general, portable hardness testers provide accurate measurements, Ames Testers’ results are in the range of ±/-1 of the actual hardness value.
Some of the most commonly used portable hardness testers include the Leeb rebound hardness tester, the ultrasonic contact impedance (UCI) tester, and the portable Rockwell tester. These testers are designed to provide quick and non-destructive measurements of hardness, making them ideal for field use and on-site testing. Portable hardness testers can provide quick and repeatable hardness test results, making them suitable for many applications. Brinell and Vickers are also commonly used in the US, particularly in laboratory settings. However, the Rockwell test is generally considered more practical and versatile for industrial and field use due to its simplicity and ease of use.
Your choice of hardness testing method will vary depending on your specific industry or application. For example, you may prefer the Knoop hardness test for measuring the hardness of thin coatings or surface layers, while the Shore hardness test is commonly used if you are in the plastics and rubber industries. It’s important to note that portable hardness testers may not be as accurate as laboratory-based testers, such as the Brinell or Vickers hardness testers. These laboratory-based testers typically provide more precise measurements, but they are also more time-consuming and require more preparation and equipment.
The Brinell and Rockwell hardness tests are both widely used and accepted methods for measuring the hardness of materials. Each test has its own advantages and limitations, and the choice of test method depends on the specific application and the type of material being tested.
The Brinell hardness test is generally considered better for measuring the hardness of materials that have a coarse or inhomogeneous microstructure, such as cast metals, because it uses a relatively large indentation and a lower test load, resulting in a larger and more representative sample area. The Brinell test also has a wider range of test loads available, allowing for the measurement of a broader range of hardness values.
On the other hand, the Rockwell hardness test is often preferred for materials with a fine or homogeneous microstructure, such as steel, because it uses a smaller indentation and a higher test load, resulting in a smaller and more precise sample area. The Rockwell test is also faster and easier to perform than the Brinell test, making it more practical for industrial and field use.
Ultimately, the choice between the Brinell and Rockwell tests depends on the specific application and the type of material being tested. In many cases, both tests may be used in conjunction with each other to provide a more comprehensive analysis of the material’s hardness and properties.
Hardness testing of metals before and after heat-treating is a common practice in manufacturing establishments like yours. Tests are made of materials before machining begins; of tools that are used and to check hardness after heat-treating.
Sheets of metals are tested to make certain they are not too hard to cause breakage of valuable dies. Bars are tested to insure proper machining speeds and protection of turning tools. Heat-treated parts are checked to control hardness within established limits for better performance and longer wear.
Ames Portable Hardness Testers are ideal for these purposes since they can be taken to the material receiving departments, to machines where you are working, and to every place by inspectors during the entire manufacturing process. Being portable, they check the hardness of parts while in machines being fabricated, and also after being assembled into complete sets.
Ames testers are used to check parts being machined that work harden under certain conditions. You test the hardness of large shear blades and cutters in machines, to check if heat developed in the operation of machines has affected the hardened shafts and parts. A book could be written on the many applications that Ames testers have found.
Customers all over the world learned to expect the best in design workmanship and accuracy in Ames hardness testers. With great pride, Ames offers portable hardness testers to all who make tests in Rockwell hardness scales. They are precisely made, carefully tested for accuracy, and beautifully finished. Enthusiastic owners, like you, have told others about Ames portable hardness testers and the savings made on a variety of interesting applications.
Until Ames Portable Hardness Testers were made in the year 1947, it was thought that only large bench-type hardness testers with weights and levers would give accurate results. Many attempts at building portable hardness testers were made by others that were failures, and the large bench machines seemed like the only accurate dependable type.
Ames employed the principle of the ordinary micrometer a C frame with a screw to perfect a lightweight, accurate easy-to-use hardness tester. Incorporating a sensitive dial indicator and graduated barrel dial, readings are taken directly in the Rockwell scales with no calculating or transposing. No skill is required by the operator, and the tests are made quickly and easily.
Ames portable hardness testers are used everywhere in a plant saving your company installation expenses, cost of transporting materials, and valuable stock that would be cut from bars and or sheets for test purposes with bench testers. Ames portable testers save you the cost of large stationary testers that would otherwise be needed in a plant. The cost of Ames testers is only a fraction of the bench-type testers.
The principle of Rockwell Hardness Testing is based on the scientifically established theory that a definite relationship exists between the hardness of a material and the depth of the penetration when the indentation method of measurement is used. The numbers of the Rockwell scales represent the depth of penetration when standard indenters are used under known pressure loads.
This method has proved practical and accurate and is the simplest and quickest method yet devised for measuring hardness, hence the universal acceptance of Rockwell scales as a standard for measuring hardness. For testing hardened steels and alloys by the Rockwell method, a standard “C” penetrator is used under a pressure load of 150 kgs. The penetrator has a 120-degree cone carefully ground and polished and a diamond point that has been mechanically lapped to a spherical point with a .008-inch radius. For testing soft steels, nonferrous alloys, and cast iron, a standard 1/16″ diameter specially hardened steel ball penetrator, known as the “B” penetrator, is used and a pressure load of 100 kgs is applied. Readings in other Rockwell scales are obtained by using the diamond penetrator and ball penetrators of 1/8″ and 1/2″ diameter and 60 and 100 kg loads.
In the Rockwell method of Hardness testing, two loads, a minor, or initial load and a major load are applied. The depth of penetration actually measured is the additional depth resulting from the major load after the initial or minor load has been applied. This causes no serious difficulty or computation as the tester is set back to zero following the initial load. The resultant reading is believed to be a truer and more accurate measurement of hardness, in as much as surface imperfections or variations in the piece would cause inaccurate readings. By measuring only the increment or additional depth caused by the major load, inaccurate readings due to surface variations are eliminated.
In the Rockwell B and C scales, the minor load is 10 kgs and the major load is 100 and 150 kgs respectively. In the Rockwell Superficial scales, the minor load is 3 kgs and the major load is 15, 30, and 45 kgs respectively. Ames hardness testers employ the same penetrators and pressure loads as specified in Rockwell hardness testing and consequently read directly in the Rockwell scales. A chart of Rockwell scales is provided with each tester giving the penetrators and pressure loads to be used. This chart also gives equivalent Brinell readings.
Your Ames Portable Hardness Tester was designed for checking the hardness of materials in the Rockwell scales. This has become an asset to the racing industry which has developed a scale* for checking clutches using the Ames Portable Hardness Tester. The Ames tester helps to win races by providing repeatable results every time.
Featured in one of our promotions, Mike Bell, team II driver for Roy Hill Drag Racing, knows how important clutch plate survival is to victory in Pro Stock. Sudden heating can affect both surface and internal structure of clutch metals. Mike used Ames Rockwell Hardness Tester model 2 to check surface hardness of both plates before installation. He used the following recommended configuration. Roy Hill Drag Racing’s Ford Thunderbird set a Pro Stock National record of 6.73 seconds in 1995.
They provide the following recommendations for testing clutches* with your hardness tester in 6 easy steps:
Step 1: Rotate the outer ring on the dial indicator and align the “dot” directly under the indicator needle. Position the clutch between the 1/2 inch ball penetrator and the 1-inch anvil. Make sure the surface is flat and the ball will not fall into holes or grooves.
Step 2: Rotate the handwheel clockwise until the needle on the gauge moves to the set position on the gauge face.
Step 3: Rotate the aluminum barrel counterclockwise so that the pin rests on top of the lucite magnifier
Step 4: Rotate the handwheel clockwise until the indicator needle reaches 60 on the indicator face.
Step 5: Immediately rotate the handwheel counterclockwise until the indicator is back at the set position.
Step 6: Read the black scale on the barrel. The thick line across the barrel is the whole number. (10, 20, 30, 40 etc.) The smaller hash marks on the left side of the barrel are in two-point increments.
Note: It has been established that using this method, test readings that fall between 65 to 80 give the best results.
You probably recognize former racing customers such as Massey Race Cars, Wayne County Speed, Stouts, Carl Smith, Glidden Racing, Ricky Smith Racing, Paul Rebeschi, Gary Brown Racing, Heck Racing, and Nickens Bros. Racing maintenance crews have come to rely on the results provided by Ames hardness testers.
*Please note that this is a special testing method designed by professionals in the racing industry for use as described in these steps and does not represent recommended testing methods for our Ames Portable Hardness Testers. In this case, the ball penetrator is used and the “B” scale is read. The ball penetrator is not used to produce readings in the “B” scale.
In May of 1977, Ames announced the release of the Ames Model ST portable Hardness Tester. This superficial tester is specifically designed for testing small diameter or thin wall tubing. The small anvil will fit into the inner wall of tubing as small as 3/16″ and is effective in checking larger sizes as well. The tube hardness tester reads in the 15-T scale and comes in a high-impact case just like our other portable hardness testers.
The Ames model ST tubing tester uses a special cylindrical anvil to test soft tubular materials such as copper. This tester is recommended for small diameter tubing with thin walls. The maximum load for the model ST is 15 KG, anything greater will damage this tester.
Before you begin a hardness test using your model ST, be sure that the 1/16 ball penetrator is snuggly screwed into the end of the tester spindle shaft. The 1/18″ pin perpendicular to the spindle is the anvil.
How to use your Model ST Tube tester:
Step 1: Rotate the bezel (outer ring of the dial indicator) and position the face of the dial so that the dot on the face is directly below the indicator’s pointer hand.
Step 2: Position your part over the 1/8″ anvil and slowly rotate the handwheel until the penetrator makes contact with the part and moves the pointer hand on the dial indicator to the line marked set. Stop at this point. You have reached the minor load point (3 kg).
Step 3: Rotate the numbered aluminum barrel dial, so that the 1/16 inch pin rests on top of the lucite magnifier.
Step 4: Rotate the handwheel until the pointer hand on the dial indicator reaches the major load of 15 kg (do not over or undershoot the target). Immediately after reaching the major load, rotate the handwheel back to the “set” (minor load) position.
Step 5: To read the Rockwell hardness, find the fine line on the magnifier. The scale below the magnifier on the aluminum barrel is graded in units of 10. The short hash marks are in units of two.
Rockwell Hardness testing is a system for determining the hardness of metals and alloys of all kinds. The American Society for Testing and Materials (ASTM) has established a standard recognized worldwide to help manufacturers maintain the qualities they want in their products. If you are using the Brinell scale check out our conversion chart.
ASTM Standards E-18 and E-110 defines the test method and parameters for a valid test using portable hardness testers. Following is a general description of the method. A spheroconical diamond penetrator or a carbide ball penetrator is forced into the surface being tested at a predetermined pressure load. The hardness is read as a function of the depth of penetration.
To overcome errors in measurement, two pressure loads are applied in sequence. The first, a minor load is applied and the readout dial is “zeroed” with the part being tested still under load. Then the major load is applied. The penetrator is backed out to the minor load point to read the distance traveled. The hardness reading represents the additional depth of penetration beyond the minor load. Tester accuracy is checked by running the test on specimens whose hardness has been certified by an independent testing laboratory. All Ames hardness testers perform genuine Rockwell Hardness tests, giving a direct Rockwell reading. Their accuracy meets or exceeds ASTM Standards E-18 and E-110. Each tester comes complete with test specimens to assure continued accuracy.
*All Ames testers are factory lubricated. Do not attempt additional lubrication. Keep the tester dry and free from oil. Store in the case provided. When necessary, wipe with a commercial cleaner
Maintaining accuracy with a portable Rockwell hardness tester
All AMES Hardness Testers, whether in constant use or not, require accuracy checks. To check accuracy, take the average of 5 readings on the test block. The readings on the barrel dial should agree with the marking on the test block, within +/- 1 point. Further, to guarantee the accuracy of your tester, it is recommended that tests be made in high, medium, and low ranges. For example, C Scale, C-63, C-50, and C-28. Once per year, your tester needs to be factory calibrated.
The distance between the center of two adjacent indentations shall be at least three times the diameter of the indentation. The distance from the center of any indentation to an edge of the test piece shall be at least two and a half times the diameter of the indentation. In other words, keep indentations 3 diameters apart. Indentations can only be made on one side of the test block.
Please check out our penetrators for hardness testing by clicking the link below
Ames began making Ames Portable Rockwell Hardness Testers in 1947. In 1975 Ames was acquired by Electro Arc. The Ames line of portable hardness testers has been made in Michigan since.
In 1997 it came to the attention of the Electro Arc company that each of it’s testers had been purchased by a company in China and duplicated. Now Chinese copies of Ames Portable Hardness testers are available online, bearing a striking resembelance to the handcrafted testers we manufacture everyday. Each of our testers are built one at a time following the ASTM E110 standard for the Rockwell scale. Each genuine Ames Hardness tester is individually calibrated to the Rockwell scales and bears a signed certificate with each tester.
How can you tell if your Ames Portable Hardness Tester is genuine?
It bears the Ames symbol within the dial indicator
Call us with the model number located on the front of your tester – we keep records of every tester we sell
Check the documentation included with your tester
How important is metal hardness testing?Consider the information provided by hardness testing and its significance in structural (i.e. bridges), aerospace, automotive, quality control, failure analysis and many other forms of manufacturing and industry. Determining material properties provides valuable insight to the durability, strength, flexibility and capabilities of a variety of component types from raw materials to finished goods.
Hardness testing is used extensively to characterize materials and to determine if they are suitable for their intended use. Why then would you buy a Chinese copy of a hardness tester?
When quality is critical, should you trust a counterfeit hardness tester?
Can it be calibrated?
Will it hold up?
Can it be serviced?
Does it really meet the ASTM standard?
Ames Hardness Testers can be repaired and calibrated at our facility in Dexter Michigan. We also service Dell models. We do not offer service for any other brands. When considering a purchase of a Rockwell Hardness Tester to insure quality, you should consider its quality, repeat-ability and reliability.