The test method is Non-Destructive which allows accurate testing on delicate or finely finished surfaces without physical or structural damage to the part, saving cost and resulting in less scrap.

This new portable UCI/Leeb hardness tester can easily convert and be calibrated to all the popular hardness scales such as, HRC, HRB, HRN, HRT, HB, and HV. Need to print your test results? USB output to a PC is built-in to this unit.

• Test steel with min thickness of .08” and unlimited max thickness (Other materials may have larger minimum thickness levels, depending on hardness)
• Blazing fast test results
• Rockwell, Brinell and Vickers hardness test conversions shown on display
• Large Memory w/USB Output
• Choice of manual UCI probes; 1kg, 2kg, 5kg & 10kg
• Optional Motorized Probes: .30kg, .80kg, & 1kgf
• Available Impact Devices(Leeb) D, DC, D+15, G & DL

Specifications:

Bob owns a mill in a small Pennsylvania town. He was losing a tremendous amount of money from lost productivity due to machinery breakdowns. He met with his maintenance supervisor and together they designed a plan to reduce downtime by implementing a method of identifying developing problems. Regular preventive maintenance checks were performed at key locations throughout the plant. Vibration readings were recorded and monitored for any changes. When there was a change, such as an increase in vibration readings on a main bearing that showed it was approaching a danger of failure, parts were ordered and bearing replacement was scheduled for a time that would not affect production.

   The Rockwell Hardness Tester was designed in 1919 by Stanley P. Rockwell. He was a metallurgist in a New England ball bearing manufacturing plant. Until this time industry lacked a good method for measuring the hardness of ball bearing races and other hardened steel parts. Mr. Rockwell studied the problem and through experimentation for accurately measuring part hardness, he invented the Rockwell Hardness Tester.

The early model of the Rockwell tester had a sturdy, hollow cast frame. The head consisted of a precise measuring dial and a plunger that held the indenter. A series of levers with a knife edge connected the plunger with a weight. This weight, originally called the "final weight" (now known as the major load), was applied and released by a hand lever. The test piece was held by an anvil on top of an elevation screw that was raised and lowered manually by the use of the capstan nut. An initial pressure (now known as the minor load) was applied by compressing a spring in the head of the tester by raising the elevation screw. The hardness was read directly from the dial face on the tester, once the final weight was removed with the hand lever.

Since the Rockwell tester was first put into use it has been refined and improved. However, the test principle remains the same. Modern Rockwell hardness testers are now available in many different models and configurations such as: Bench models in both digital and analog, Portable models, Automatic/Production models, and Load cell models.

Pictures are of our Wilson-Maeulen Co. Rockwell Hardness Tester model 2-1/2-A circa 1924.

Hardness testing has been around for many years. Each method was developed based on needs such as the hardness of a certain material, part shape, thickness and/or part size. As with most things, one size does not fit all, so to speak, which is basically why there are many different variations of hardness test methods like Vickers, Brinell, and Leeb impact.

The most commonly used hardness test method is the Rockwell hardness test. This is largely due to the ease of use and that the result is read directly from the tester dial or digital readout. The Rockwell number comes from the distance that a diamond indenter or ball penetrator is forced into a material by a set load beyond the initially set pre-load or minor load.

Softer material such as plastic, soft steel, copper and aluminum require the use of a 1/16", 1/8", 1/4" or 1/2" carbide ball penetrator. The ball size is determined by which scale is being used. Hard materials such as hardened steels and carbide require the use of a diamond indenter.

There are two types of Rockwell testing; Regular and Superficial. Regular Rockwell testing uses a 10 kilogram minor load and the major load will be 60, 100 or 150 kilograms. Superficial uses a minor load of 3 kilograms and a major load of either 15, 30 or 45 kilograms. The deeper the indenter or penetrator is forced into the material, the lower the Rockwell reading. Rockwell readings are broken down into scales that are each designated by a letter that signifies the minor load, major load and type of indenter or penetrator required for the test. Most hardness testers have a chart on them that shows the various scales that the tester can test in or you can refer to a Rockwell Hardness Scale Chart.

How do you determine which scale to use? First look at the material type. If it is steel, is it soft or is it heat treated and hard? Second look at the thickness of the part. If it is too thin, the indenter or penetrator may push through and give you a false reading and possibly damage the anvil. Hardness vs Minimum Thickness Charts are available to assist in determining the best scale to use for a certain material and thickness. After looking over the chart you may find that more than one scale can be used. It is a good rule of thumb to choose the scale with the heavier load. The heavier load will make a larger indentation and cover a larger area of the material. The reading that you get from the test will be more representative of the material as a whole. Apply this same principle when determining the hardness of a case hardened part with a known case depth.

In regards to cold working of the material by the indenter, the depth of material affected has been found to be about ten times the depth of the indentation. Therefore, unless the thickness of the material being tested is at least ten times the depth of the indentation, an accurate Rockwell test cannot be expected. Refer to a Hardness vs Minimum Thickness Chart as a guide to help determine which scale to use for your material thickness.

Make sure you do a trial test before you lock-in on a scale. If you see a bulge on the underside of the test area, the material was not thick enough for the load applied. This is known as the anvil effect and it indicates that the Rockwell scale applying the next lighter load should be used. When too much force is applied on soft material that is too thin, flow of the material will result. Keep in mind that when the anvil effect or flow of the material is present, the Rockwell hardness value most likely will be false. It is not recommended to stack several thin test pieces until a recommended minimum thickness or better is obtained. There may be slippage between the layers that will affect the result and you will end up with false readings. 

It is very important to have at least three indentation diameters of distance from the center to center of each indentation. The reason for this is that the area that the indentation was made will be cold worked and have an effect on readings of the next test, if the indentation is too close to the affected area. The softer the material, the more attention needs to be placed to proper spacing. Don't get too close to the edge of the test piece or the material will yield. The distance from the center of the indentation to the edge of the test piece or test block should be at least two and one half indentation diameters.

While Rockwell hardness numbers should be reported on the same scale that the actual test was made, Hardness Conversion Charts are available and should typically be used as a guide. If for some reason converted values must be reported, be sure that your initial test was performed accurately and that the converted numbers are noted as such. Proper use of the conversion chart requires a proper reading to convert from.

The Rockwell hardness tester is a very durable piece of precision equipment that is suitable for use in a variety of locations including laboratories, production floor, heat treating, incoming inspection and more. The tester must be kept clean and in good calibration, and along with proper use, should provide accurate results in diverse applications and material types.

By Jeff Briley

Owner, Brystar Tools

Many engineers may seem like they have this problem when it comes time to measure the thickness of steel container or thick concrete building wall. These measurements can only be completed with the right measurement tools.

Most thickness measurements are done with a ruler, micrometer or caliper. There are many manufactured parts and required measurement areas that can't be accessed with these measuring tools.

The development of the Ultrasonic Thickness Gauge has allowed part thickness measurements without having access to the other side of the part, which is required with most typical measuring techniques.

I'll give you a couple of examples from our customers' applications:

Bob operates old steam engines and he is required to measure the wall thickness of the steam engine boiler for quality purposes. Getting an accurate measurement of the thickness of the walls is only possible with the use of an Ultrasonic Thickness Gauge. It is important to monitor the wear on the inside of the boiler but physically being able to reach both sides of the part that needs to be measured cannot be easily accomplished.

Jackson, another customer, is in the concrete business and thickness measurements are made on the product transfer tubes to determine when they need to be replaced.

In both of these cases it would be very difficult to determine wall thickness without a Ultrasonic Thickness Gauge. 

By Jeff Briley

Owner, Brystar Tools

He would cut samples of the steel sheets and coil stock and carry them to the testing lab on the other side of the building. He used a Wilson Rockwell hardness tester to test the 20 or so different samples each day. Most of his day was taken up with testing and recording all of the results leaving little time to do in-process inspection reports. It did not take him long to realize that if he could take the tester to the material, he could save a tremendous amount of time.

Donald decided on a Phase II MET-U1A portable ultrasonic hardness tester for the job. What a time saver! He could now carry the tester with him to the material receiving area and test the material on the spot. He did not have to record all of his readings by hand anymore because this tester saves each test in its memory. What was taking him hours each day was cut down to about half an hour. When he was done testing, he plugged in the USB cable into his ultrasonic tester and uploaded the results onto his computer.

By Jeff Briley

Owner, Brystar tools

Material has many different fundamental properties but hardness is not one of them. Hardness values were determined by a chosen method of a set load by a conceived point geometry on a material for a set amount of time. The National Institute of Standards and Technology NIST has the objective to standardize hardness measurements and has the responsibility for traceability in hardness measurements. The hardness test procedure standard was developed by the American Society for Testing and Materials ASTM and the International Organization for Standardization ISO.

Before the development of the hardness tester, hardness was determined by a variety of methods. One of the earliest was a comparison of material hardness using the scratch method. This is done by taking a scratch tool of desired hardness and attempting to scratch a sample materials surface with it. If it scratches the surface, the tool is harder than the sample material. If the tool does not scratch the sample material then the sample is harder than the tool.

By Jeff Briley     Owner, Brystar Tools

Testing the hardness of case hardened steel provides important information about the hardness and depth of the case. The "case" is the harder outside layer and the inner part is called the "core". When testing hardened material it is very important that the depth of case is adequate to support the indenter properly. The case depth should be at least 10 times the depth of the indentation. For instance, if the hardness of the case is HRC62 and the depth of the indentation is .003", the case depth must be at least .030". This is necessary to obtain an accurate reading. Let's say a HRC test is made and the result is less than HRC62. This may mean that the case hardness is too soft or that the case depth is less than .030". If you were using a superficial Rockwell hardness tester on the HR15N scale the minimum case depth would need to be .015".

 It would be important to know what the case depth actually is by using a microhardness tester. Case depth can be recorded as either "effective case depth" or "total case depth". Effective case depth is a depth at which a minimum specified hardness value is achieved. Total case depth is the depth at which hardness becomes equal to the core hardness. There are several methods used to determine this. One of the most common is the cross section hardness traverse method using a microhardness tester and graphing the results. Microhardness tests are more time consuming than Rockwell tests so once the case depth is determined then production runs could be monitored with a regular or superficial Rockwell tester, depending on the case depth.

By Jeff Briley

Owner, Brystar Tools