Short answer: "INOX" on a cutting disc means the wheel is formulated free of iron, sulphur and chlorine — the contaminants that embed in stainless steel and destroy its corrosion resistance. It matters as much as how fast the wheel cuts.
What INOX actually means
INOX comes from inoxydable, French for stainless. On an abrasive wheel it is not a marketing word for "thin" or "fast" — it is a statement about composition.
Stainless steel resists corrosion because chromium in the alloy forms a thin passive oxide layer. Anything that breaches or contaminates that layer creates a corrosion site.
An INOX-designated wheel is manufactured to be free of iron, sulphur and chlorine (often written Fe/S/Cl-free). Cutting stainless with an ordinary steel wheel presses free iron particles into the fresh cut face. Those particles rust, and because they are embedded in the surface, the rust appears to bloom out of the stainless itself.
This is the cause of the "tea staining" or rust spotting that shows up days or weeks after fabrication — long after the job has been signed off.
Why the damage appears late
Free-iron contamination is not visible at the time of cutting. The cut looks clean and bright.
What follows is:
- Embedded iron particles oxidise on exposure to moisture.
- Rust spots appear on and around the cut edge.
- The passive layer is locally compromised, so corrosion can continue into the parent metal.
- Pitting can begin at those sites, particularly in humid, coastal or chemical environments.
For food-grade, pharmaceutical, dairy, chemical and architectural stainless work, this is a rejection. Remediation means pickling, passivation or re-machining the affected surfaces — far more expensive than the disc.
Heat is the second problem
Stainless steel has lower thermal conductivity than carbon steel, so heat concentrates at the cut instead of dissipating into the workpiece. It also work-hardens readily.
Consequences of excess heat:
- Blue and straw discoloration — a heat tint that itself indicates a degraded passive layer
- Carbide precipitation at grain boundaries in the heat-affected zone, reducing corrosion resistance
- Work hardening ahead of the cut, making progress slower and wheel wear faster
- Distortion in thin sheet and tube
This is why thin wheels matter for stainless. A 1.0 – 1.6 mm disc removes less material, generates less heat and cuts faster than a 3 mm disc. See Ultra Thin Wheels (INOX) and Cutting Disc Thickness: Thin vs Standard Wheels.
Technique that protects the passive layer
- Use a dedicated INOX wheel and keep it dedicated. A wheel previously used on mild steel carries iron.
- Cut, do not dwell. Steady moderate pressure, let the wheel work. Forcing generates heat without cutting faster.
- Keep the wheel moving rather than holding it in one spot to "burn" through.
- Never side-grind a cut-off wheel — see Grinding Wheel vs Cutting Wheel.
- Segregate tooling. Separate wheels, brushes and clamps for stainless. Carbon-steel wire brushes reintroduce iron.
- Avoid steel-contaminated benches. Grinding dust from mild steel settles on stainless and rusts in place.
- Deburr with stainless-safe abrasives — see Flap Discs and Sanding Discs.
Choosing a stainless cutting wheel
| Requirement | What to look for |
|---|---|
| No contamination | INOX / Fe-S-Cl free designation |
| Minimum heat input | 1.0 – 1.6 mm thickness for sheet, tube, thin section |
| Clean fast cut | Zirconia or aluminium oxide grain suited to stainless |
| Safety compliance | EN 12413 marking with maximum operating speed |
| Correct shape | Type 41 flat or Type 42 depressed centre for cutting |
| Machine match | Wheel rpm at that diameter above machine no-load speed |
For heavier stainless section where a thin disc would be fragile, a reinforced wheel in a stainless-safe formulation is the better balance — see Reinforced Cut-Off Wheels.
For grinding and weld dressing on stainless rather than cutting, use a stainless-suitable Depressed Centre Wheel, and see How to Choose the Right Grinding Wheel for Stainless Steel.
Where it matters most
- Food processing, dairy and beverage plant
- Pharmaceutical and clean-room fabrication
- Chemical and petrochemical piping
- Architectural stainless, handrails and cladding
- Water treatment
- Coastal and marine installations
In each case the cost of a rejected weld or a corroded handrail is far higher than the price difference between an ordinary disc and an INOX disc.
Frequently asked questions
What does INOX mean on a cutting disc?
That the wheel is formulated free of iron, sulphur and chlorine so it will not contaminate stainless steel.
Can I cut stainless steel with a normal cutting disc?
Mechanically yes, but it deposits free iron in the cut, which later rusts and reduces corrosion resistance.
Why does my stainless steel rust after cutting?
Almost always free-iron contamination from a non-INOX wheel or a carbon-steel brush, or heat damage to the passive layer.
Can I use an INOX wheel on mild steel?
Yes, it cuts mild steel fine — but once used on mild steel it is contaminated and should not go back onto stainless.
What thickness is best for cutting stainless?
1.0 – 1.6 mm for sheet, tube and thin sections; step up only when section thickness demands rigidity.
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Cutting stainless in production? Tell us the grade, section size and volume and we will recommend an INOX specification from the Apidor range. Request a quotation or view all products.