Custom Fasteners Hardness standards: Rockwell vs Vickers vs Brinell

Rockwell, Vickers, and Brinell all attempt to determine a material’s susceptibility to indentation or deformation when a force presses on its surface.

Hence, manufacturers utilize them to evaluate the hardness of materials, including custom fasteners, to try to assess their strength and durability.

Although they share the same goals, there are significant differences in techniques and common applications.

Learn more here about the three hardness standards and how to apply the appropriate one to your fastener manufacturing.

Rockwell vs. Vickers vs. Brinell: Overview of Hardness Testing Methods for Custom Fasteners

Rockwell Test or HR Testing

It measures the indentation depth by pressing a diamond cone (known as a brale) or a tungsten carbide ball indentation into the material with minimal force and then increasing it.

The attached YouTube video could help you visualize how this hardness test works.

Rockwell Hardness Test Scale

Rockwell used several indenters and loads to test a wide range of fastener materials, designs, and testing environments.

Thus, Rockwell has a number of scales, including the Regular Rockwell scale, which is designed for higher loads and harder materials. Examples involve the following:

• HRC (scale C)
• HRB (Scale B)
• HRA (scale A)
• And much more

Meanwhile, the superficial Rockwell scale is for lower weights for tinier, softer, and thinner materials, which include:

• 15N
• 30N
• 45N
• 15T
• 30T
• 45T
• And so on

The hardness number estimated from the indentation depth will be followed by the letters “HR” and the Rockwell scale identifying letter that is being used.

For example, if the hardness number is 60 and the Rockwell scale is C, the written result should be 60 HRC.

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Pros and Cons

This testing method is commonly used on fasteners since it requires less additional equipment and is better suited for tougher materials such as alloys and steel. Moreover, it enables quick durability assessment with little surface preparation and causes only small item damage.

However, Rockwell has difficulty testing smaller fasteners with sizes less than 0.2 mm since the smallest available indenter is about 0.2 mm in diameter. In addition, surface-hardened fasteners can generate false microhardness measurements by mixing the hardness values of the surface layer with the underlying material.

Brinell Hardness Test or BHN Testing

Consists of measuring the size of the indentation left by pressing a large steel or tungsten carbide ball into the material, resulting in significant deformation.

Here’s a YouTube video that clearly illustrates this hardness test’s process.

Brinell Hardness Test scale

Brinell scales are based on a set of indenter ball sizes and testing pressures. They usually have 1 to 10 mm ball diameters and up to 3000 kg loads.

Here are some of the common Brinell scales:

• HBW 1/30
• HBW 10/500
• HBW 10/3000
• HBW 2.5/187.5
• And so on

The hardness number should be written first, followed by the HBW, the size of the indenter used, and the applied force in kilograms.

For instance, 450 HBW 10/3000 indicates that the Brinell hardness is 450 with a 10 mm tungsten carbide ball under a 3000 kgf load.

Pros and Cons

This testing is better suited for custom fasteners with large surfaces as well as curved, rough, and coarse-grained structures, which are easier to measure than Vickers’ small indentations. Furthermore, it has a greater load range than the other two.

Similar to other hardness tests, it has limits such as being slower and producing larger deformations, making it less suitable for finished custom fasteners.

Vickers Hardness Test or HV Testing

This method employed a diamond-shaped indenter with a 136° angle between opposing faces, which was inserted into the fastener under a particular load.

Similar to the Brinell’s hardness test, it examines the indent size rather than its depth.

To help you understand this test better, here’s a visual demonstration from YouTube.

Vickers Hardness Test Scale

Vickers is recognized for its general scale suited for practically all fastener materials, which are:

• Micro Vickers: 10 g to 1000 g load
• Macro Vickers: 1 kg to 100 kg load

Furthermore, the hardness value of the item under testing will be followed by “HV” and the test pressure in kilograms. If the time length of the applied load exceeds 10 to 15 seconds, you may add a dwell time frame after the test pressure.

To demonstrate, the result should be recorded as 356 HV 10 if the hardness value is 356 with a 10 kgf load, or 356 HV 10/25 if the dwell time of 25 is included.

Pros and Cons

It provides fastener microstructural analysis and precise hardness assessment, including fasteners with thin coatings and surface-hardened layers.

Unfortunately, it was more time-consuming and required more comprehensive requirements, like a microscope and clean surface testing for fasteners, to get accurate results. Lastly, it is unsuited for curved, rough-surfaced, and coarse-grained fasteners because it makes it difficult to distinguish the indentation edges.

Rockwell vs. Vickers vs. Brinell: How Hardness Testing Helps Prevent Fastener Failures in Critical Applications?

All hardness testing techniques help manufacturers confirm a fastener’s ability to withstand deformation, wear, and damage, which are critical for structural integrity.

It identifies product flaws as well that may cause failures or accidents by ensuring the item’s capacity to endure factors like dynamic loads and corrosive environments over its entire lifespan.

Therefore, manufacturers can confirm whether the items match specific safety standards, strength, and material qualities to meet their clients’ needs.

Hardness testing is also an efficient and non-destructive approach to ensuring product quality, especially for fasteners that cannot be tensile tested to evaluate strength.

Rockwell Hardness Test vs. Brinell Hardness Test vs. Vickers Hardness Test: Frequently Asked Questions

Can you convert Vickers to Rockwell?

You can only roughly convert Vickers hardness (HV) to Rockwell hardness (HRC) because the two tests employ different indenters and approaches.

To achieve greater accuracy, use official hardness conversion tables rather than simple formulas when converting Vickers hardness.

Which factors affect the selecting of the appropriate hardness test?

The factors that affect selecting appropriate hardness tests include the item’s material type, size, structure, necessary accuracy, required test load, and the application’s quality requirements.

Why are Vickers hardness values more reliable than Brinell hardness values?

Vickers hardness ratings are more reliable because of its durable diamond indenter, which is less susceptible to deformation when exposed to high force than Brinell’s.

Furthermore, Vickers made smaller and clearer indentations than Brinell’s larger ones, allowing for more exact and accurate measurements.

Rockwell vs. Vickers vs. Brinell: Key Takeaways

Each method is recognized for its distinct advantages, such as Rockwell’s speed and easiness, Vickers’ precision, and Brinell’s large load range and ability to test coarse-grained structures.

All of these ways enable manufacturers to improve the process control and material integrity of their customized fasteners.

CNRL is one of the manufacturers that guarantees that custom fasteners are of high quality, durable, and meet mechanical properties standards.

As part of our rigorous quality control, our custom fasteners portfolio supports and ensures that they exceed Rockwell, Vickers, and Brinell hardness criteria.

Contact CNRL now to obtain a tailored fastener solution with approved quality testing and enhance your production process.