Steel Hardness Reference
Description
HRC and Vickers hardness scales explained for hair scissor steels. Understand what hardness numbers mean for edge retention and performance.
Steel Hardness Reference
Quick look
- HRC (Rockwell C Scale): The industry-standard hardness measurement for scissor steels, ranging from ~48 HRC (budget) to 67 HRC (maximum).
- HV (Vickers Hardness): A micro-indentation test used for harder materials and coatings where Rockwell reaches its limits.
- Key insight: Hardness alone does not determine cutting performance—carbide structure, wear mechanism, and toughness all matter.
Why it matters
Every scissor steel discussion eventually lands on HRC numbers. Buyers compare them like horsepower figures, assuming higher always means better. The reality is more nuanced. Understanding what hardness tests actually measure—and what they miss—helps stylists make informed purchasing decisions and avoid marketing traps that conflate a single number with overall quality.
Rockwell C Scale (HRC) explained
The Rockwell C test presses a diamond-tipped cone (ブレール圧子/Brēru asshi) into the steel surface under a 150 kg load and measures the depth of penetration. A shallower indent means harder steel. The test is fast, repeatable, and non-destructive enough for production use, which is why it became the default for the scissor industry. However, HRC measures resistance to localised plastic deformation—it does not directly measure edge retention, wear resistance, or toughness.
Vickers Hardness (HV) explained
The Vickers test uses a square-based diamond pyramid indenter under lighter, precisely controlled loads. It measures the diagonal of the resulting micro-indent under magnification. Vickers is preferred for very hard materials (above ~65 HRC), thin coatings, and micro-hardness mapping across a blade cross-section. Ceramic blade materials like zirconia are typically rated on the Vickers scale because they exceed the practical range of Rockwell testing.
HRC to HV conversion table
| HRC | HV (approximate) | Typical steels at this range |
|---|---|---|
| 48 | ~484 | 2Cr13, budget stainless |
| 50 | ~513 | 3Cr13, entry student shears |
| 52 | ~544 | 4Cr13, basic professional |
| 54 | ~577 | 420J2, standard stainless |
| 56 | ~615 | AUS-8, 5Cr15MoV |
| 58 | ~653 | 440C, 8Cr13MoV, 10Cr15CoMoV |
| 60 | ~697 | VG-10, cobalt alloy |
| 62 | ~746 | VG-XEOS, premium cobalt |
| 64 | ~800 | SKD-11, HAP40, PM steels |
| 65 | ~832 | Nano Powder Metal |
| 67 | ~900 | HYS-MAX67 (Hayashi) |
Conversions are approximate and follow ASTM E140 standard tables. Actual values vary with test conditions and material properties.
Scissor hardness tier table
| Tier | HRC range | Representative steels | Typical application |
|---|---|---|---|
| Budget | 48–52 | 420, 2Cr13, 3Cr13 | Student, training, disposable |
| Entry professional | 53–56 | 4Cr13, 5Cr15MoV, AUS-8 | First professional scissors |
| Mid-range | 56–59 | 440C, 8Cr13MoV, 9Cr13CoMoV | Everyday salon workhorses |
| Premium | 59–62 | VG-10, cobalt alloy, VG-XEOS | Daily-driver precision cutting |
| Ultra-premium | 62–64 | SKD-11, SG powder, nano PM | Specialist dry cutting, editorial |
| Maximum | 65–67 | HAP40, HYS-MAX67 | Artisan, custom, competition |
Why HRC alone does not tell the full story
Two steels at identical HRC can behave completely differently in a scissor. The reason lies in how they wear. Conventional high-carbon steels wear by micro-chipping: tiny fragments break from the edge apex, creating a sawtooth pattern that feels “draggy.” Cobalt-enriched steels wear by gradual abrasion: the edge rounds slowly and uniformly, maintaining a functional cutting feel much longer even though the measured hardness may be lower.
This is why a cobalt alloy at 60 HRC can outperform a harder steel at 63 HRC in real-world salon use—the cobalt steel’s edge degrades predictably rather than catastrophically. Factors beyond hardness that determine cutting performance include:
- Carbide size and distribution: Smaller, evenly distributed carbides support a finer edge.
- Toughness (resistance to fracture): Harder steels are more brittle; toughness determines how the edge fails.
- Wear mechanism: Abrasive wear vs. micro-chipping vs. corrosive wear each respond differently to hardness.
- Heat treatment quality: Two identical alloys with different heat treatments will perform differently at the same HRC.
Sources
- ASTM E140 – Standard Hardness Conversion Tables
- Hitachi Metals (Proterial) – Steel Properties Reference
- Japan Scissors – Hair Scissor Steel & Materials Guide
- Engineering Toolbox – Rockwell Hardness
Related: Composition Guide • Steel Types • Cobalt Alloy