Stainless Steel CNC Machining

Stainless steel is one of the most demanding materials in CNC machining. Its low thermal conductivity (15 W/mK) — roughly 10× worse than aluminum — leads to extreme heat concentration at the cutting edge. At the same time, stainless steel has a strong tendency toward work hardening and built-up edge formation.

Despite these challenges, stainless steel is indispensable in many industries: food processing, medical technology, chemical, pharmaceutical, and marine. Its excellent corrosion resistance, good hygiene properties, and high strength make it the standard material for demanding environments.

Stainless steel requires an adapted machining strategy:

Golden rule: Never dwell in the cut with stainless steel! The cutting edge must always be engaged — otherwise the surface hardens and tool wear increases exponentially.

• Food Industry — Valves, housings, conveyor systems (1.4301, 1.4404)
• Medical Technology — Implants, surgical instruments, sterile containers (1.4404, 1.4441)
• Chemical & Pharmaceutical — Reactor components, agitators (Duplex, 1.4571)
• Marine & Offshore — Shaft components, fittings (1.4404, Duplex)
• Mechanical Engineering — Wear parts, shafts in corrosive environments

Work hardening is the biggest challenge in stainless steel machining. The surface becomes harder than the base material through plastic deformation. Here’s how to avoid this:

• Never dwell in the cut: When the tool stops, the surface hardens immediately. On the next cut, the layer is harder — the tool needs more force and wears exponentially faster.
• Never feed too low: Too low feed generates more friction than cutting. Minimum 0.05 mm/tooth for milled parts — preferably a bit more.
• Prefer climb milling: In climb milling, the cut starts with maximum chip thickness — the edge immediately penetrates below the hardened layer.
• Use sharp tools: Dull tools push instead of cutting. Tool change intervals with stainless steel 30–50% shorter than with carbon steel.
• Stable clamping: Vibrations lead to fluctuating depth of cut — and thus work hardening in the wave troughs.

Stainless steel offers diverse surface options:

Important: After CNC machining, stainless steel should always be passivated. During machining, foreign iron remains on the surface, which can lead to flash rust. Passivation in nitric acid or citric acid removes these contaminants.

For many industries, mill certificates and traceability are mandatory:

• 3.1 Certificate (EN 10204): Material certificate with chemical analysis and mechanical properties. Standard for pharma, food, and medical technology.
• Batch traceability: Every component is traceable via batch number back to the raw material supplier.
• First Article Inspection Report (FAIR): Dimensional report with all critical dimensions — standard for first orders.
• Surface inspection: Roughness measurement (Ra, Rz) with report on request.

At Strobel Industry, you receive all certificates and inspection reports as PDF on request. → Contact