Rockwell vs Brinell vs Vickers hardness testing: which method to use

Definition: Rockwell, Brinell and Vickers are the three indentation hardness methods used in industry; they differ in the indenter (diamond cone, hardened ball or diamond pyramid), the test force (from a few grams-force to 3000 kgf) and in what is measured (indentation depth for Rockwell, indentation diameter or diagonal for Brinell and Vickers).

1. How each method works

1. Rockwell (ISO 6508-1, ASTM E18, IS 1586). A diamond cone (120°, 0.2 mm tip radius) or a steel/carbide ball is pressed in with a preliminary force of 10 kgf (98.07 N), then with a total force of 60, 100 or 150 kgf (588.4, 980.7 or 1471 N). The hardness number comes directly from the permanent depth of indentation: one Rockwell unit equals 0.002 mm. No microscope is needed, so a reading takes 5 to 10 seconds.
2. Brinell (ISO 6506-1, ASTM E10, IS 1500). A tungsten-carbide ball of 1, 2.5, 5 or 10 mm diameter is pressed in with a force chosen so that 0.102 × F/D² equals 30 (steel, cast iron), 10 (copper and aluminium alloys), 5, 2.5 or 1. The most common combinations are HBW 10/3000 (29.42 kN), HBW 5/750 and HBW 2.5/187.5 (1839 N). The operator measures the diameter of the impression with a microscope or camera and reads the value from a table or software.
3. Vickers (ISO 6507-1, ASTM E92 / E384, IS 1501). A diamond pyramid with a 136° angle between opposite faces is pressed in with a force from 10 gf (micro-Vickers) up to 100 kgf and beyond. Both diagonals of the square impression are measured; HV = 1.8544 × F/d² with F in kgf and d in mm (0.1891 × F/d² with F in newtons). Because the pyramid is geometrically similar at every depth, the HV number is, in principle, independent of the test force.

2. Comparison at a glance

3. When to use Rockwell

Rockwell is the workhorse of production inspection because the reading needs no operator judgement. Use HRC (150 kgf, diamond) for hardened and tempered steel, tool steel and deep case-hardened parts in the 20–70 HRC band; HRB (100 kgf, 1/16″ ball) for soft steels, brass, bronze and aluminium up to about 100 HRB; HRA (60 kgf, diamond) for cemented carbides and thin hardened strip. The superficial scales (15N, 30N, 45N with the diamond; 15T, 30T, 45T with the ball) cut the total force to 15–45 kgf so that nitrided layers, thin sheet and small parts can be tested without breaking through the case.

Its limits: the indentation is small, so on cast iron or coarse forgings a single reading can land on a graphite flake or a hard phase and mislead. Rockwell also needs a firm, clean seat — a dirty anvil or a burr under the part reads low.

4. When to use Brinell

Brinell is the right choice whenever the material is not homogeneous: grey and SG iron castings, steel forgings, rolled bar, aluminium castings and large weldments. A 10 mm ball under 3000 kgf averages the hardness over an impression several millimetres across, so the result represents the bulk of the material. Brinell is also the most tolerant of a rough, as-cast or flame-cut surface. HBW 10/3000 covers steel and cast iron; HBW 10/1000 and 10/500 cover copper and aluminium alloys; small balls with the same force ratio (HBW 2.5/187.5, HBW 1/30) let a bench-top tester such as a Rockwell-cum-Brinell machine test smaller parts.

Its limits: the impression is large and deep, so Brinell cannot be used on thin sheet or finished surfaces, and the practical upper limit is about 650 HBW with carbide balls. Measurement by eyepiece microscope is operator-dependent; camera-based measurement removes most of that scatter.

5. When to use Vickers

Vickers covers everything from soft aluminium to sintered carbide with one indenter and one scale, which makes it the reference method for laboratories. At low forces (HV 0.1 to HV 1) it is the standard for case-depth traverses, weld cross-sections, plating and coating thickness, heat-affected zones and individual micro-constituents. At 5–50 kgf it serves as an alternative to Rockwell on small or thin components where the Rockwell ball or cone would exceed the 10 × depth rule.

Its limits: each reading needs a polished surface and an optical measurement, so throughput is lower and vibration or poor lighting affects the result. The impression is also very sensitive to a surface layer, which is exactly why it is used for coatings.

6. Converting between scales

There is no physical law linking the three numbers. Conversion tables (ASTM E140, ISO 18265) are empirical and material-specific — the steel table must not be used for aluminium or copper alloys. As a rough orientation for carbon and alloy steel: 60 HRC ≈ 697 HV; 40 HRC ≈ 392 HV ≈ 371 HBW; 20 HRC ≈ 238 HV ≈ 226 HBW; 100 HRB ≈ 240 HBW; 80 HRB ≈ 150 HBW. Always report the scale actually used, and specify the scale — not a converted value — on drawings.

Frequently asked questions

Which ETS machine

• Rockwell hardness testersDial, digital and touch-screen models with 60/100/150 kgf loads; Twin models add the 15/30/45 kgf superficial scales.
• RASNB Rockwell-cum-Brinell testerAdds 187.5 and 250 kgf loads for HBW 2.5/187.5 and HBW 5/250 on the same bench; also available digital (RASN-250-D) and fully automatic (RASNB-TSFA).
• Brinell hardness testers250–3000 kgf machines with camera measurement for castings and forgings (B3000-PC, B3000-TS, ETS-LCB-3000AT).
• Vickers hardness testersVcB-250 optical Vickers-cum-Brinell (5–120 kgf) and the VM 50-TSPC touch-screen PC model for case depth and coatings.