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.
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.
Ames Portable Hardness testers read in the Rockwell scale. The Rockwell scale uses indentation and measures the depth of that indentation with a major and minor load to determine the hardness of a metal. The scale used depends of the metal being tested and the portable hardness tester used.
Ames developed a conversion chart for use in converting Rockwell scale readings into the Brinell scale. This allows you to easily determine the equal Brinnell reading. This conversion chart is broken down into categories to help you determine the converted value.
Hardened Steel and Hard Alloys, locate the type of penetrator you used and the scale you used in the top column for the scale. In this case you will only see C, A, D, 15N, 30N and 45N scales which can then be converted into the Brinell scale. Follow the appropriate line across to locate the corresponding reading in the middle column marked ‘Brinell’.
The next section is Soft Steel, non-ferrous metal, grey and malleable iron casting, this section covers the B, E, F, G, 15T, 30T and 45T scales. You will need to find the appropriate load in order to find the correct conversion. The bottom of this conversion chart includes corrections which cover any readings that were not included in the original chart.
The right-hand side of the chart gives you a guide to choosing the appropriate penetrator and hardness scale for your metal.
Ames introduced the model 8 hardness tester in February of 1975. This portable hardness tester has the capacity for either rounds or flats up to 8 inches to determine the hardness of metals and alloys in various Rockwell scales.
See the Model 8 Hardness Tester in Action!
The model 8 Ames portable Hardness Tester saves time and money by its ability to be taken to the workpiece being tested rather than having to cut pieces off to be taken to the laboratory for testing. The measuring head is independent of the measuring clamp or machine tool holder of your own design.
The model 8 Ames Portable Hardness Tester is accurate, light to carry, and easy to use. This tester meets the needs of both large and small plants. Use model 8 to test standard Rockwell scales, this tester is convienently is supplied with a carrying case.
With a frame depth of 4 inches, this tester reads Rockwell A, B, C, and other scales. The measuring head may be removed and mounted on a tool holder. This tester weighs 8.25 pounds.
Do you wonder if Ames portable hardness testers are the best option for you to use when testing the hardness of metal? Here are 5 reasons to choose Ames when you choose your hardness tester.
Ames provides you with repeatable accuracy. Repetative tests on the material will give you in the same reading. You may not find this benefit generally available on competing hardness testers. You will experience no loss of accuracy when you transfer your readings into Rockwell scales. This is because all readings are made directly into Rockwell scales. Ames tester accuracy may be compared to the accuracy of bench-type testers when you perform tests in the smae enviornment.
Ames hardness testers are simple for you to operate. Even unskilled users can learn to make accurate tests after a very limited period of practice. This means you do not need highly qualified inspectors to make hardness tests. This allows you to perform hardness testes more frequently, and provide your customers with maintenance and closer tolerances for their products.
Portable testers can be taken anywhere. With hardness testers that are not confiened to the labratory you can perform hardness tests on material at the assembly line, in the receiving yard, or on material still assembled in the machine. You will avoid delays in production. You can also perform hardness tests in scenerios that are not accessable for use with bench style hardness testers.
Test in Rockwell A, B, and C. Ames portable hardness testers allow you to test directly in regular Rockwell A, B and C scales, or in Rockwell Superficial N and T scales. You can simply change the penetrator and the major load and your tests can be made in Rockwell D, E, F, G, H, K, L, M, P, R, S and V scales. You can refer to the following conversion chart for Rockwell Hardness. Ames’ extensive line of portable hardness testers allows you to test material in a size range of 1mm to 1 meter in diameter.
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.