Metal CNC Machining Material
Stainless steel is an iron alloy with at least 10.5% chromium. CNC machining cuts it into precise, corrosion-resistant parts. We machine it for medical, food, marine, and chemical equipment.
Grade Guide
Stainless comes in families. Austenitic grades (304, 316) resist corrosion and are non-magnetic. Martensitic grades (416, 420, 440C) are hard and magnetic. Precipitation-hardening grades (17-4 PH) are very strong. These are the ones we machine most.
Free-machining austenitic. The easiest stainless to cut. Great for screws, nuts, and turned parts.
The most common grade. Excellent corrosion resistance and formability. Non-magnetic. Used for food and medical parts.
Marine grade. Added molybdenum boosts resistance to salt and chemicals. Best for marine, chemical, and medical use.
Precipitation-hardening. Very strong (up to ~1000 MPa) yet machinable before aging. Aerospace and high-stress parts.
Martensitic, free-machining. Magnetic and hardenable. Good for shafts, valves, and gears.
Martensitic with high hardness after heat treatment. Used for cutlery, blades, and wear parts.
High-carbon martensitic. The hardest stainless we machine. Bearings, bushings, and tools.
Ferritic, magnetic, good corrosion resistance and polishability. Used for decorative and automotive trim.
Not sure which grade to pick? Send us your drawing. Our engineers will suggest the best stainless for strength, corrosion, and cost.
Specifications
Typical values for 304, the most common CNC grade. Exact numbers change with the grade and temper. We confirm the right grade during your DFM review.
| Property | Typical Value | Notes |
|---|---|---|
| Material family | Iron + chromium alloy (≥10.5%) | Stainless steel |
| Density | 8.0 g/cm³ | About 3× aluminium |
| Tensile strength (304) | ~515 MPa | Varies by grade |
| Tensile strength (17-4 PH) | ~1000 MPa | After aging |
| Hardness (304) | ~85 HRB | 303 harder, 440C much harder |
| Melting point | ~1400–1450 °C | Much higher than aluminium |
| Corrosion resistance | Excellent | Self-healing chromium oxide layer |
| Magnetic | Varies by grade | 304 non-magnetic, 416/440C magnetic |
| Machinability | Good (303 best) | Work-hardens if mishandled |
| Food & medical safe | Yes (304 / 316) | Hygienic and biocompatible |
For reference, 303 reaches about 517–620 MPa tensile, 316 about 570 MPa, and 17-4 PH up to ~1030 MPa after aging. Tell us if your part needs extra strength.
The Process
CNC machining is a subtractive process. A computer-guided machine cuts away metal to shape your part. Stainless needs sharp tools and steady cutting to avoid work hardening.
Upload STEP, IGES, or STL files. We review them for free and flag any issues early.
We use CAM software to plan toolpaths. Sharp carbide tools and the right speeds keep cutting clean.
CNC mills or turns the stainless. We keep a steady cut and use coolant so the surface does not work-harden.
We remove burrs and apply passivation, electropolish, or blasting as your part needs.
We check dimensions against your drawing and ship your parts worldwide.
Why Choose Stainless
A chromium oxide layer protects it. Great indoors, outdoors, and underwater.
High tensile strength. 17-4 PH reaches about 1000 MPa after aging.
304 and 316 are hygienic and biocompatible. Used in surgical and food tools.
Keeps strength at high temperature far better than aluminium.
Smooth, non-porous surface. Simple to polish and keep sanitary.
Resists wear, rust, and fatigue. Low total cost over time.
Things to Watch
Light cuts or a stopped tool harden the surface. We use sharp tools and keep a steady cut.
Harder than aluminium. Needs rigid setups and the right speeds.
About 3× the weight. Not ideal for weight-critical parts.
Heat builds up at the tool. Plenty of coolant controls it.
Harder to cut, so cycle times and cost are higher than aluminium.
420 and 440C need care. We pick or avoid grades by your design.
All of these are managed by good tooling and process control. Our free DFM review plans for them before we cut.
Where Stainless Is Used
Instruments, implants, surgical tools, and hygienic housings.
Valves, fittings, tanks, and processing equipment that must stay clean.
Boat hardware and fittings that resist seawater and corrosion.
Pumps, valves, and vessels for corrosive fluids and gases.
Brackets, fasteners, and high-stress components built to last.
Gears, shafts, machine parts, and pressure or vacuum vessels.
Finishing
Stainless already resists rust, but finishes add protection, hygiene, or looks. Pick what your part needs.
Acid treatment (ASTM A967) that removes free iron and boosts corrosion resistance. The standard finish.
Smooth, mirror-like, and hygienic. Ideal for food and medical parts.
Matte satin texture that hides tool marks and gives a soft feel.
Bright, decorative shine for visible or premium parts.
Directional satin look for trim, panels, and appliances.
Dark, mild corrosion protection and a stealth, non-glare look.
Design Guide
Good design keeps stainless parts accurate and avoids work hardening. Follow these rules.
Sharp edges cut cleanly and avoid work hardening the surface.
Light or stopped cuts harden the surface. Take consistent depths.
Stainless needs stiff fixturing and tooling to stop chatter.
Controls heat and clears chips. Never dry-cut stainless.
Internal radii reduce stress and tool wear. Avoid sharp inside corners.
Standard ±0.05 mm. On controlled runs we hold ±0.005 mm.
Passivation and electropolish add almost no thickness, so they barely change dimensions.
Our Service
We are a China-based factory with CNC, 3D printing, and injection molding under one roof. We take your stainless part from prototype to production.
Complex shapes cut in one setup for high accuracy.
Round parts, shafts, and threaded components made fast.
From one part to high-volume runs, with consistent quality.
In-house and partner finishes, including passivation and electropolish.
Engineers optimize your design for cost, speed, and quality.
Parts ship from our Dongguan factory to your door, worldwide.
Get a Quote
Send STEP, IGES, STL, or PDF drawings. The more detail, the better our quote.
We review your design and return a quote with free DFM feedback within 24 hours.
Approve the quote. We machine your stainless parts and ship them to you.
FAQ