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What do you need to know before buying a hardness tester?

Looking to measure hardness? Let’s explore the various methods of measuring the hardness of metals, along with the advantages and disadvantages of each.

Typically, if you need to measure the hardness of metals, the situation looks like this: you have a product with technical specifications, including a parameter such as hardness, which is defined by a range in specific units, for example, 20-25 HRC or 100-150 HB. But what does this mean?

To understand this, let’s delve into the history, back to when pioneers in the field of material property research were racking their brains to find the best method for measuring hardness. There are three most common methods for measuring hardness:

Brinell hardness testing

This method was first proposed in 1900 by Swedish engineer Johan August Brinell. Its principle is based on pressing a ball of a specific diameter into a material under a specific load. The operator then measures the diameters of the resulting indentation using a microscope and calculates the hardness value in HB units using a special formula. Later, tables with predefined diagonal lengths were developed to speed up the process of obtaining hardness values without manual calculations. Soon the hardness testing became one of the key quality parameters of metal alloys.

Rockwell hardness testing

A little later, in the early 20th century, an alternative method was introduced by Hugh and Stanley Rockwell. It addressed some of the drawbacks of the Brinell method, such as the slow testing process and the large indentation, which made it far from being non-destructive. This method involved pressing a cone into the material and measuring the depth of the indentation, which the machine calculated automatically using a built-in micrometer. This eliminated the need for the operator to use a microscope, thus reducing operator influence on the results.

Vickers hardness testing

With the increasing demands for the quality of metal products, technologies for hardening surface advanced, and requirements for surface increased. This raised the need for measuring hardness of surfaces and thin-walled products. The first method to address these needs was proposed by the British military-industrial company Vickers-Armstrongs, Ltd. The method involved pressing a four-sided pyramid into the surface of the material with a relatively small load, followed by measuring the diagonals of the indentation under a high-magnification microscope.

There are also other direct methods of measuring hardness, such as those by Ludwig, Shore, Martens, and others. However, they have not gained widespread popularity, so we will omit their discussion in this article.

To summarize, here is a table highlighting the key features of the methods:

Feature\ Method	Brinell	Rockwell	Vickers
Unit of Measurement	HB	HR	HV
Type of Indenter	Steel ball	Diamond cone tip/steel ball	Diamond tip in the shape of a square pyramid
Measurement Principle	Measuring the diameter of the ball indentation	Measuring the depth of indenter penetration	Measuring the diagonal of the pyramid indentation
Application Area	Large workpieces, non-uniform materials	Mass quality control	Coatings, thin materials
Testing Complexity	Requires microscope measurements and calculations	Simple to use	Requires more precise microscope measurements and calculations

Let’s now return to the task at hand, for example, “HRC hardness testing.” Do we need to immediately purchase a Rockwell C hardness tester? To answer this, let’s take a closer look at what a hardness tester is and what its features are.

A classic hardness tester, which determines hardness using the direct method (by embedding a hard body (indenter), into the product and evaluating the damage it causes), is a stationary device whose weight, depending on the type, ranges from several dozen to more than hundred of kilograms.

This device is installed on a special workbench, usually a massive metal table with a hole for the movement of the test bench screw. The hardness tester typically requires connection to the power grid and is sensitive to temperature and humidity conditions in the room where it is used.

The size of the product that can be tested is typically only a few centimeters in width and height, meaning that to test pipes or large items, you would have to cut a piece off to place it on the tester’s workbench. The measurement time, excluding sample preparation for testing, takes from 1 to 10 minutes, if we take into account that the hardness of the product is recommended to be determined by 3-5 points, you can estimate the resulting productivity yourself.

And most importantly, if you purchase a stationary hardness tester, you’ll need to pay a considerable sum for the device itself, plus shipping costs, particularly if the device is shipped internationally by a logistics company. Additionally, you’ll need to equip the workstation as described above and account for the necessary training of personnel, as only highly qualified staff should operate such equipment.

Are you ready for all of this? And are such costs acceptable for solving your task?

Everyone who faced the challenge of measuring hardness encountered similar problems. A simpler method was needed that would allow for quick testing without being tied to a workstation. It took people about 50 years to find alternative solutions, resulting in the development of portable hardness testers that no longer require the use of stationary devices for hardness testing according to Brinell, Rockwell, and Vickers scales.

Today, there are many portable hardness testers that implement both direct and indirect methods for hardness measurenent. These testers can provide measurements according to the Brinell, Rockwell, Vickers, or any other scale you require. The most popular worldwide are:

Ultrasonic Hardness Testing
(UCI method)

Developed by Dr. Klaus Klezzatell in 1961, this method is based on measuring the change in frequency of a resonating rod (indenter) when it makes contact with the test sample under a specific load. This method allows for hardness measurements of products with virtually no mass or thickness limits—starting from 100g and 1mm thickness. Measurements take only 1-2 seconds, and the indentation left is invisible to the naked eye.

Leeb Hardness Testing
(Dynamic method)

This method invented in 1975 by Swiss engineer Dietmar Leeb. Its principle is based on determining the ratio of the rebound velocities of a striker that impacts the surface of the sample, before and after the collision. This method also allows for measurements in 1-2 seconds, leaves a little larger indentation, and is applicable to heavier objects, starting at 5 kg and 10 mm thickness. However, it is less sensitive to the surface and material homogeneity compared to UCI testers.

Devices that implement these methods typically weigh less than 0.5 kg, fit into a small bag or case, operate on standard or built-in rechargeable batteries, and can be used in various field or workshop conditions.

The measurement is made directly on the product, meaning there’s no need to move or cut the product into pieces, even if it’s large. The measurement time is just a few seconds, without the need to wait for applied testing loads or microscope measurements. The indentation, especially for the UCI method, is microscopic—just a few tens of microns—which makes these methods virtually non-destructive. In contrast, with the Brinell method, the indentation can be over 5 mm.

And most importantly—price. These devices are much more affordable compared to their bulky predecessors!

Of course, it’s not to say that indirect methods of measuring hardness can completely replace direct ones, as there are nuances related to calibrating indirect methods for various specific alloys. However, 90% of all tasks encountered in the modern world can be solved using such devices.

Let’s take a look at some of the features and characteristics of different types of hardness testers:

Feature\Method	UCI Hardness Tester	Leeb Hardness Tester	Classic Hardness Tester
Measurement time	1-2 seconds	1-2 seconds	1 to 10 minutes
Minimum weight of the item	From 100 g	From 5 kg	From 100 g*
Minimum thickness of the item	From 1 mm	From 10 mm	From 1 mm*
Portability	++	++	–
No damage to the item during testing	++	+	–
Ability to test in hard-to-reach areas	++	+	–
Ability to test massive objects	+	+	–
Does not require high personnel qualification	+	+	–
Affordable price	+	++	–

* It depends on the type of device, method or testing load.

In our product range, we offer hardness testers based on all the methods and principles described above. To help you finalize your choice of equipment, please contact us in any way that is convenient for you, and our specialists will be happy to assist you in selecting the optimal solution for your needs.

Phone: +38 067 593 59 77

Phone/Whats App: +38 067 513 2094

E-mail: [email protected]

What do you need to know before buying a hardness tester?

Brinell hardness testing

Rockwell hardness testing

Vickers hardness testing

Ultrasonic Hardness Testing (UCI method)

Leeb Hardness Testing (Dynamic method)

To contact the head office, please complete the following form:

Ultrasonic Hardness Testing
(UCI method)

Leeb Hardness Testing
(Dynamic method)