Why stainless steel needs a special approach
Stainless steel is an alloy of iron with chromium (minimum 10.5%), which forms an invisible passive layer of chromium oxide (Cr₂O₃) on the surface. It is this layer that protects the metal from corrosion. And it is this that makes the processing of stainless steel fundamentally different from the processing of ordinary steel.
Three main problems when processing stainless steel:
- Iron contamination - iron particles from a regular cutting disc are embedded in the surface of the stainless steel, destroying the passive layer. After weeks, rust appears in these areas.
- Heat sensitivity - stainless steel has low thermal conductivity (3 times lower than carbon steel). Heat is concentrated in the cutting zone, and not dispersed throughout the workpiece. Overheating destroys the protective layer.
- Heat affected zone (HAZ)— at temperatures above 300°C, chromium reacts with carbon to form chromium carbides. The zone near the cut loses its corrosion resistance — this is called sensitization.
- Strain hardening (hardening) - during processing, the surface layer of stainless steel becomes significantly harder. Each subsequent pass over the same place is harder than the previous one. The metal also "smeared" onto the abrasive grains, quickly clogging the surface of the wheel.
INOX Rule: No Fe or S
The main rule when working with stainless steel: all tools must be free of iron (Fe) and sulfur (S). This applies to cutting discs, grinding discs, flap discs, fibre discs and even brushes.
How to recognize the right disc for stainless steel:
Key features of the disc for INOX:
- INOX or stainless steel marking on the label is mandatory
- Lack of iron and sulfur in the composition of the binder and filler
- Grain - zirconium corundum (ZA) or ceramic (SG), but not ordinary aluminum oxide with iron-containing additives
- Label color is usually blue or green (NovoAbrasive has blue for Profi INOX)
Choosing an INOX cutting disc
For cutting stainless steel, thin cutting discs marked INOX are required. Thickness is a critical parameter: the thinner the thickness, the less heat is transferred to the workpiece.
| Thickness | Appointment | Advantages for INOX | Limitation |
|---|---|---|---|
| 1.0 mm | Thin sheet stainless steel up to 3 mm, profile | Minimum heat, fastest cut | Requires careful work, does not allow lateral loads |
| 1.2 mm | Sheets up to 5 mm, pipes up to 30 mm | Balance between speed and stability | Slightly more heating |
| 1.6 mm | Pipes, fittings, rolled products up to 15 mm | Longer life, stable cutting | Noticeable heat input - short passes |
| 2.0 mm | Large cross-sections, thick walls | Maximum resource | Significant heating - only when necessary |
Grain type for INOX
- Zirconium corundum (ZA) - Profi INOX series. Self-sharpening grain, stable performance. The optimal choice for everyday work
- Ceramics (SG) - Extreme series. Microcrystalline grain with minimal heat release. For critical structures and large volumes
Choosing an INOX grinding disc
Grinding stainless steel is a separate task that requires special abrasive tools. There are two main types:
Flap Discs
The best choice for grinding stainless steel. The abrasive skin flap discs are placed one on top of the other in a disc, ensuring even wear and a smooth finish. Always marked INOX.
| Grit / Grain Size | Task | Result |
|---|---|---|
| P40-P60 | Weld removal, rough grinding | Fast metal removal, rough finish |
| P80 | Surface leveling, scratch removal P60 | Flat surface, preparation for finishing |
| P120 | Finishing sanding, preparation for polishing | Smooth surface with minimal burrs |
| P240 | Fine finishing sanding | Semi-mirror surface |
Fibre Discs
Fibre discs are mounted on the back plate of the grinder and are more aggressive than flap discs. Use them to quickly remove large amounts of metal, such as stripping welds. For INOX, choose discs with zirconia or ceramic grain P60-P80.
Stainless steel cutting technique
Proper technique is as important as the right tool. Stainless steel is unforgiving—overheating or excessive pressure immediately affects quality.
Basic cutting rules
- Short passes - cut 3-5 seconds, pause 2-3 seconds. This allows the metal to cool between passes
- Moderate pressure - let the abrasive do its work. Excessive pressure increases heat generation and accelerates disc wear
- Color control - if the metal near the cut turns yellow, blue or purple, you are overheating. Reduce pressure and increase pauses
- No pendulum movements - drive the disc straight, without swinging to the side. Lateral load can break a thin disc
- Correct angle - hold the grinder at a 90° angle to the surface, without tilting
Optimal parameters
| Parameter | Recommendation for INOX | Why is this important? |
|---|---|---|
| Speed | Maximum for this disk | High speed = less contact = less heat |
| Pressure | Moderate (weight of the tool + light pressure) | Excessive pressure overheats and deforms |
| Cutting duration | 3-5 seconds, then pause | Prevents heat build-up |
| Cooling | Air or water-soluble emulsion (5-8%) | Reduces temperature, prevents chills |
Finishing: Grain consistency
A good stainless steel finish is always a consistent transition from coarse to fine grain. Each subsequent step removes scratches from the previous one. You can’t skip steps — the scratches will remain.
Step 1: P60 - weld removal
P60 flap disc or P60 fibre disc for quick removal of excess weld. Work at a 15-30° angle to the surface, in even passes along the weld. Do not linger in one place.
Step 2: P80 - Alignment
P80 flap disc for smoothing the surface and removing deep scratches from P60. This step is critical - any scratches left after P80 will be visible on the finished surface.
Step 3: P120 - preparation for the finish
P120 flap disc to create a uniform matte surface. At this stage, the surface should look uniform, without individual scratches or pits.
Step 4: P240 - Finishing Surface
P240 flap disc or non-woven material for final finishing. The result is a uniform semi-mirror surface, ready for use or further polishing.
Typical errors when working with INOX
- Using a regular (not INOX) disc. Iron and sulfur contaminate the surface. Rust appears after weeks — exactly in the cut areas. It can only be fixed by stripping and passivation.
- Overheating during cutting. Blue or purple discoloration indicates heating to 300-400°C and destruction of the protective layer. Use thin 1.0 mm discs and work in short passes.
- Wrong grit sequence. Jumping from P60 to P120 or P240 doesn't remove deep scratches - they just become less noticeable, but they're still there. Don't skip steps.
- Using the same tools for mild steel and stainless steel. Even ordinary steel residue on a workbench, vise, or clamps will contaminate stainless steel. Keep a separate set.
- Too much pressure when cutting. Pressing does not speed up the cut - it increases heat and wear on the disc. Let the abrasive do its work, only add weight to the tool.
- Sanding against the grain. Chaotic movements create messy scratches that are impossible to hide. Always sand in one direction, along the visible line.
Stainless steel grades: AISI 304, 316, 430
Stainless steel is a family of alloys with different properties. The three most common grades in construction and industry require different processing approaches:
| Brand | Type | Chrome/Nickel | Application | Processing features |
|---|---|---|---|---|
| AISI 304 | Austenitic | 18% Cr / 8% Ni | Food industry, architecture, railings, handrails | The most common. Tough, easy to rivet. Profi INOX is the optimal choice |
| AISI 316 | Austenitic | 16% Cr / 10% Ni / 2% Mo | Chemical industry, marine equipment, medicine | Molybdenum makes it more viscous. Requires more time to cut. Ceramic grain (Extreme) recommended |
| AISI 430 | Ferrite | 17% Cr / 0% Ni | Home appliances, car parts, decor | Less viscous, easier to cut. Magnetic (unlike 304/316). Profi INOX is enough |
Austenitic (304, 316) vs Ferritic (430)
Austenitic stainless steels (304, 316) are the most common and most difficult to machine. They are non-magnetic, very ductile, and susceptible to work hardening (hardening of the surface during machining). Ferritic (430) are magnetic, less ductile, and easier to machine.
The main difference in processing:
- 304 is the standard INOX approach. Profi INOX discs are optimal. Moderate pressure, short passes
- 316 - increased complexity. Extreme series (ceramics) recommended. Reduced pressure, increased pauses. Molybdenum makes the metal "sticky" for the abrasive
- 430— easier to process. Profi INOX is enough. Heats up less, cuts better. But the INOX rule (without Fe/S) remains mandatory
Other types: martensitic (AISI 410, 420) - hardened, used for knives and medical instruments. Duplex - a combination of austenitic and ferritic structures, used in the chemical and oil and gas industries. Both types require INOX discs and recommend the Extreme series due to increased hardness.
NovoAbrasive INOX series
NovoAbrasive produces a full line of stainless steel tools in two series:
All NovoAbrasive INOX products undergo mandatory testing for the absence of Fe and S in the composition. MPA Hannover certification - NovoAbrasive is the only Ukrainian manufacturer with this certificate. Production on Davide Maternini equipment (Italy) using European raw materials (Austria, Germany).
Frequently asked questions
Why can't you cut stainless steel with a regular cutting disc?
Conventional cutting discs contain iron (Fe) and sulfur (S) in their composition. When cutting, these elements are introduced into the cut zone of the stainless steel, disrupting the passive protective layer of chromium. After a few weeks, rust appears in the cut areas - the so-called contamination. Use only discs marked INOX.
What thickness of cutting disc should I choose for stainless steel?
For stainless steel, choose thin discs 1.0-1.6 mm. A thinner disc heats the metal less, which is critical for INOX - overheating causes discoloration (tarnishing), deformation and loss of corrosion resistance. Discs 2.0+ mm are justified only for large diameter pipes.
How to polish stainless steel without scratching?
Use a grit sequence from coarse to fine: P60 for weld removal, P80 for smoothing, P120 for preparation for finishing, P240 for finishing. Each subsequent pass should remove scratches from the previous one. Use flap discs marked INOX.
What is the difference between the processing of AISI 304 and AISI 316?
AISI 316 contains molybdenum, which makes it more ductile and heat-resistant. It heats up more during processing and loads the disc more. For 316, ceramic grain ( Extreme series ) and reduced pressure are recommended. AISI 304 is more common and easier to process, Profi INOX discs are suitable.
How to determine that the wheel needs to be replaced?
The main signs of wear: a sharp increase in cutting time, the appearance of sparks of an unusual color, sticking and runaway on the workpiece, increased tool vibration. When working with stainless steel, the wheel needs to be replaced before its wear is visually noticeable - do not wait until the diameter decreases to the minimum.
What to do if stainless steel has changed color after cutting?
Discoloration (fading) is a sign of overheating and damage to the protective layer. A blue or purple hue means heating to 300-400°C. Remove the damaged layer by grinding or chemical etching (passivation). To avoid this, make short passes, do not press hard, and use thin discs.
Choose a tool for INOX
NovoAbrasive's complete line for stainless steel: cutting, flap and fibre discs with INOX marking