Materials
420 stainless steel
The workhorse martensitic stainless for blades, jaws and tips that need to be hard and stay clean.
A short history
Stainless steel is usually credited to Harry Brearley of Sheffield, England, who in 1913 produced a hardenable steel of roughly 13% chromium while looking for a gun-barrel steel that resisted erosion. It was soon used for cutlery, and martensitic chromium steels of this family became the backbone of cutting tools and hand instruments.
Composition
- Chromium
- 12–14%
- Carbon
- ≥ 0.15% (typically 0.15–0.40%)
- Manganese, silicon
- ≤ 1% each
- Structure
- Martensitic — hardenable by heat treatment
Steel counts as stainless when it carries at least about 10.5% chromium (the threshold used in the European standard EN 10088). The chromium reacts with oxygen to form an extremely thin, self-repairing chromium-oxide film on the surface. This passive layer is what stops rust. It re-forms on its own after light scratching, provided the surface is clean and exposed to air.
How it's hardened and tempered
Martensitic stainless steels are hardened in three steps: austenitizing (heating to roughly 950–1,050 °C so carbon dissolves into the steel), quenching (rapid cooling, which locks the structure into hard martensite) and tempering (reheating to a lower temperature to trade a little hardness for toughness, so edges and tips don't chip or snap). Exact temperatures depend on the grade and the part. 420 has more carbon than 410, so it reaches a higher hardness after quenching and holds a finer edge.
Why it lasts
- Hardenable: the carbon content lets the steel become hard enough to keep a sharp, aligned cutting edge on clippers and nippers.
- Corrosion resistant: about 13% chromium forms the passive layer, so it resists rust from water, hand creams and normal salon use far better than plain carbon steel.
- Polishes well: martensitic stainless takes a mirror or satin finish, and a polished surface is also more corrosion resistant than a rough one.
- Can be resharpened: the steel is solid all the way through, so honing exposes more of the same steel instead of a coating.
Care tips
- Rinse and dry after use; don't leave tools wet or soaking.
- Disinfect with products made for stainless tools and follow the contact time on the label; avoid bleach and chloride-heavy solutions, which can cause pitting.
- Store dry, ideally in a case, so edges don't knock together.
- A drop of light oil on the joint keeps the action smooth.
Compared with cheaper alternatives
| Feature | 420 stainless (hardened) | Chrome-plated carbon steel | Non-hardenable stainless (e.g. 304) |
|---|---|---|---|
| Holds an edge | Yes — hardenable | Yes at first | Poorly — too soft for fine edges |
| Rust resistance | Built into the steel | Only while plating is intact; rusts once it chips | Very good |
| Resharpenable | Yes | Sharpening removes the plating | Limited |
| Lifespan | Long, with care | Short once plating fails | Edges dull quickly |
Where we use it
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