Stainless Steel CNC Machining
Key takeaways
- Stainless steel offers excellent corrosion resistance, strength, and a hygienic surface — ideal for medical, food, and marine parts.
- 304 is the most common grade; 316/316L for superior (marine/medical) corrosion resistance; 303 for easy machining.
- Stainless work-hardens and machines slower than aluminum, so it costs more — but holds tight tolerances and takes fine finishes.
- Get an exact price with an instant quote from your CAD file.
Stainless steel CNC machining produces strong, corrosion-resistant parts for demanding environments. Stainless is harder to machine than aluminum and tends to work-harden, so it requires rigid setups, sharp tooling, and proper feeds — but the result is durable, hygienic parts with excellent finishes. This guide covers the common stainless grades, properties, finishes, and applications.
Stainless steel grades we machine
| Grade | Key properties | Best for |
|---|---|---|
| 303 | Free-machining (added sulfur), not ideal for welding | Fittings, shafts, fasteners, high-volume turned parts |
| 304 | Most common, good corrosion resistance, weldable | General parts, food & kitchen, enclosures |
| 316 / 316L | Superior corrosion resistance (marine, chemical), low carbon (L) | Medical, marine, chemical, food processing |
| 17-4 PH | High strength, precipitation-hardening, heat-treatable | Aerospace, high-stress, valves |
| 416 | Free-machining, magnetic, hardenable | Shafts, valve parts, gears |
| 430 | Magnetic, lower cost, decorative | Trim, appliances, brackets |
Properties of stainless steel
- Corrosion resistant — chromium oxide layer resists rust and chemicals
- Strong and durable — higher strength than aluminum
- Hygienic — easy to clean, ideal for medical and food contact
- Heat resistant — performs at elevated temperatures
- Work-hardens — machines slower and costs more than aluminum
Surface finishes for stainless parts
As-machined, bead blasting, passivation (restores corrosion resistance), electropolishing, brushing, polishing, and PVD coating.
Tolerances
Standard ISO 2768-m (±0.1 mm), with critical features to ±0.01 mm via precision machining. Rigid fixturing and sharp tooling keep tight tolerances repeatable on work-hardening grades.
Applications
Medical devices and surgical instruments, food and beverage equipment, marine hardware, chemical processing, automotive, and consumer products.
Machining tips
- Choose 303 for easy machining, 304 for general use, or 316/316L for the best corrosion resistance.
- Stainless work-hardens — consistent feeds and sharp tools prevent glazing.
- Add passivation for parts exposed to moisture or chemicals.
Frequently asked questions
What stainless steel grades do you machine?
Common grades including 303, 304, 316/316L, 17-4 PH, 416, and 430, selected to match your strength, corrosion, and machinability needs.
What is the difference between 304 and 316?
Both resist corrosion, but 316 adds molybdenum for superior resistance to chlorides and chemicals — preferred for marine and medical parts.
Is stainless steel harder to machine than aluminum?
Yes. Stainless work-hardens and cuts slower, so machine time and cost are higher than for aluminum.
Can you passivate stainless steel parts?
Yes. Passivation removes free iron and restores the protective chromium-oxide layer for maximum corrosion resistance.
What tolerances can you hold on stainless steel?
Standard ISO 2768-m (±0.1 mm), with critical features to ±0.01 mm using precision machining and rigid setups.
Which stainless grade is best for medical parts?
316L is widely used for medical and surgical parts thanks to its corrosion resistance and low carbon content.
Related services
Explore the services that use this material:
- CNC machining services
- CNC aluminum machining
- Precision machining
- Surface finishing
- All CNC machining materials
Get your parts machined
Upload your CAD file on our Request a Quote page for a free DFM review and price — from a single prototype to low-volume production, with global shipping.