Hardness, as applied to most materials, and in particular metals, is a valuable, revealing, and commonly employed mechanical test that has been in use in various forms for over 250 years. Certainly, as a material property, its value and importance cannot be understated, the information from a hardness test can complement and often be used in conjunction with other material verification techniques such as tensile or compression to provide critical performance information. How important and useful is material and hardness testing? Consider the information provided and its significance in structural, aerospace, automotive, quality control, failure analysis and many other forms of manufacturing and industry. Determining these material properties provides valuable insight to the durability, strength, flexibility, and capabilities of a variety of component types from raw materials to prepared specimens, and finished goods. Over the years, various methods for determining the hardness of materials have been developed and employed at varying levels of success. From early forms of scratch testing to sophisticated automated imaging, hardness testing has evolved into an efficient, accurate, and valued material test method.

As the 20th century progressed and endured two world wars, with the simultaneous blossoming of the industrial revolution, increased manufacturing requirements and global industrialization brought an urgent demand for more refined and efficient test methods and new techniques began to develop. Accurate, efficient forms of testing were needed in reaction to heavy manufacturing demands, structural failures, and the need to design sufficient material integrity into the growing global infrastructure.

Today, hardness testing plays an important role in materials testing, quality control, and acceptance of components. We depend on the data to verify the heat treatment, structural integrity, and quality of components to determine if a material has the properties necessary for its intended use. Through the years, establishing means of increasingly more productive and effective testing through refining traditional testing design has given way to new cutting edge methods that perform and interpret hardness tests more effectively than ever before. Hardness tests very useful in industrial and R&D applications and in insuring that the materials utilized in the things we use every day contribute to a well-engineered, efficient, and safe world.

The David L. Ellis Co., Inc. is getting a lot of calls about Ultrasonic Hardness Testers.  The problem is “How do you calibrate the tester?”  The answer is “Special Material" Blocks.  We can help you.  Give us a call.

If you have a “Leebs” tester we can calibrate it for you.  We recommend you have dual calibration on the blocks.  Example: If you use HRC, get the block calibrated to HRC NIST and LD.  If it is another scale (HRB Vickers, etc.) we can do dual calibration.

If you use Leebs, the standard blocks that come with the tester is HRC 58.  If the tester is used to check HRC 25, HRBW AL, etc., you should get a block close to what you are testing.  We have LD & LG blocks from HBW AL to HRC 58.

                                                                                                                                    - David L Ellis Co., Inc.

Direct Verification of Hardness Testers and Documentation

May 23, 2018, Acton, MA: By now some of you have heard rumors about testers failing direct verification and are not allowed to be used for qualifying parts or test items.  This requirement can be found in ASTM E18-17e1 appendix A1.  Please look at Table A1.1.  It states that new testers must have direct verification.  The basic issue is that old testers may not have ever had direct verification even when new, or there are no documents to prove it was ever done.

As a result now some accreditation bodies may require this direct information.  If it cannot be shown, then direct verification can be attempted.  At issue is whether the old tester meets ASTM E18-17e1 appendix A1.  It is a near 100% certainty that the old testers will fail.  Usually the forces and depth measurements are incorrect.  In addition, it is virtually impossible to control the dwell times of the testing cycle as they are controlled by individuals.

Having said all that, it is an option to have the tester directly verified.  It is a time consuming and an expensive undertaking.  If it still fails, which it probably will, you will have spent a significant amount of money and still need to buy another tester that meets ASTM E18-17e1 appendix A1. 
This requirement has existed since 2007, but it has not been enforced by auditors until recently.

                                                                                                                    - Robert Ellis, Quality Manager

Hardness – An Overview

April 25, 2018, Acton, MA: Hardness testing of metals, composites and minerals is the resistance to indentation, introduced by diamond or tungsten ball, and it is determined by measuring the permanent depth of the indentation. The hardness test is a fast and cost effective method for determining the condition of a material following heat treatment, ease of machining, or to provide insight into strength and wear resistance.

Rockwell, Brinell and Vickers/Knoop hardness testing is the most widely used method for determining the hardness of a material. Generally, the surface should be flat and sanded smooth to obtain an average of three of more readings.

The Brinell Hardness Test is utilized to measure hardness over a larger sample areas. Brinell hardness is particularly useful for castings and forgings that have a rough surface or micro structure too coarse for other hardness testing methods. The most common test in the USA is the Rockwell HRC for hard steel and HRBW for soft alloys. Thin metals are tested with Rockwell superficial scale. Brinell testing is often performed with a high test load (500 to 3000 kg most common in the USA) and a 10mm size indenter so the resulting indentation averages out most surface and sub-surface inconsistencies. The resulting impression is measured across at least two diameters and results averaged. The averaged diameter measurement is then converted to a Brinell hardness number.  The lower loads with a 5, 2.5, and 1mm ball are very common in other parts of the world.

                                                                                                                                    - David L Ellis Co., Inc.

Is hardness important in everyday life?

Yes, it is.

If you want to know how and why, rent and see CSI “Chasing The Bus” (Season 2, Episode 18, 2002). Sometimes hardness is a life or death situation!

http://www.cbs.com/shows/csi/video/jRN0Mk9ak7BB_Eq9RpYSjVH4aXI12rSz/csi-chasing-the-bus/

We service and provide certificates for most Hardness Testers in the field. Portable Hardness Testers (Leebs, Shore, Rockwell, Brinell, Impressor, Ultrasonic) are calibrated in house. Recalibration and reconditioning of Brinell, Rockwell, Micro, Macro Leeds blocks are available
upon request.

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Hardness Test Blocks

We offer the largest Hardness Test Block selection in the industry. If you don't see what you're looking for - Ask! All of our Hardness Test Blocks come with Accreditation. All the blocks are calibrated and accredited to ISO guide 25 and will meet automotive and aerospace standards. The HRC test blocks are calibrated on the new NIST level.

Calibration Kits

The David L. Ellis Co., Inc. offers
two types of gridded blocks for Rockwell test blocks

ASTM E-10

ISO 6506

All of our Brinell Test Blocks come with accreditation to applicable standards. We adhere to a strict procedure for the calibration of these blocks, and the accuracy of the tester is maintained using a proving ring and load cell both traceable to N.I.S.T. The readings themselves are done using a stage micrometer also calibrated and traceable to N.I.S.T.

Test Conditions and Recommended Hardness Range

Note: Circle and gridded blocks available at additional cost. Dimensions for the most common blocks will be 6" x 2" x 3/4". The other dimensions are 6" x 41/2" x 3/4" or 2" x 2". Depends on ASTM E10-17 rules for dimensions. Call for prices and availability. Material used - steel, brass or aluminum depends on hardness.

For more information, or to place an order please E-mail our sales department at:

sales@dlellisco.com, fax us your Purchase Order at: 978.897.0844,
or call us toll-free at: 800.472.6962. Please specify your desired hardness range, when ordering.

Items Shipped UPS / FedEx or as directed.

Q: How long do hardness blocks last?

A: Some blocks can last several years, though blocks can self-destruct in a short time from heavy use. Generally, soft blocks and high force testing can destroy a block in a matter of a month or so, especially if daily verification is required.

It is possible that a block become rendered useless due to changes in ASTM and ISO requirements. Such as the case of pre-NIST traceable HRC in 2000 and pre-E18-07a blocks calibrated without verified indenters.

Q: I asked for a 300 HV 0.5 micro-indentation test block and they sent me a 370 HV 0.5. I needed it to check a special part that I was manufacturing. Why can’t I get the exact value that I want?

A: Test blocks are used to verify the tester calibration, not your part. While it is desirable to get a block as close to your part hardness, it is not critical. Having said that, blocks are chosen from various heat treat lots to match the best possible. Also, different force and indenter combinations can affect the outcome of the block value you receive.

It is suggested that you look at the recommended hardness levels listed in ASTM and ISO documents.

Q: I am not sure what hardness scale to use. How can I find out?

A: A good place to start is part specifications within your company or your customer. Sometimes part specifications are listed with a common scale such as HRC, even though that scale can not be done on your part. This could be because the part is too thin or has a case hardness. ASTM and ISO charts give guidance on minimum thickness.

Be careful when using a tester by conversion or one that can electronically convert hardness scales. You can’t accredit conversions.

Find a distributor of David L. Ellis Co., Inc. products near your location.