Why choose 316 over 304 stainless?

316 contains 2–3% molybdenum, which dramatically improves resistance to chlorides and pitting corrosion. Choose 316 for marine environments, salt exposure, chemical processing, and many medical and pharmaceutical parts. For general use without chloride exposure, 304 is more cost-effective.

What is the difference between 316 and 316L?

316L has lower carbon (≤0.03%), which prevents carbide precipitation at weld zones and so resists intergranular corrosion after welding. 316L is the better choice for welded assemblies; standard 316 has slightly higher strength for non-welded parts. We stock both.

Is 316 stainless harder to machine than 304?

Slightly — 316's machinability is around 36% versus about 45% for 304, and it work-hardens similarly. We use sharp rigid tooling, positive feeds and plenty of coolant. Parts come out clean and accurate; the cut simply runs slower, which is reflected in lead time and price.

Is 316 good for medical and food parts?

Yes. 316/316L is a standard for surgical, pharmaceutical and food-contact components because of its corrosion resistance and cleanability. We passivate and can electropolish parts to a bright, hygienic surface.

316 / 316L Stainless Steel CNC Machining — Properties & Uses

When Corrosion Resistance Has to Be Serious

316 is 304's tougher sibling. The key difference is 2–3% molybdenum, which transforms resistance to chloride attack and pitting — the failure modes that destroy ordinary stainless in salt water and aggressive chemicals. That single addition makes 316/316L the standard for marine hardware, chemical processing, pharmaceutical and many surgical and food-contact parts. It costs more than 304 and machines a little slower, so it's the right choice specifically when the environment demands it.

Batch of CNC-machined 316 stainless steel fittings by EKINSUN — Stainless fittings — 316 is chosen where chlorides and chemicals would attack 304.

316 Mechanical & Physical Properties

Property	Typical value (316, annealed)
Ultimate tensile strength	≥515 MPa
Yield strength (0.2%)	~205 MPa (316L min ~170)
Elongation at break	~40%
Hardness	~79 HRB (~150–170 HB)
Density	8.0 g/cm³
Elastic modulus	193 GPa
Composition	~16–18% Cr, 10–14% Ni, 2–3% Mo
Magnetism	Essentially non-magnetic (annealed)
Machinability	~36% — work-hardens

316L's low carbon (≤0.03%) resists weld-zone (intergranular) corrosion, so it's preferred for welded assemblies. We machine to certified mill spec and supply certs on request.

316 Chemical Composition

316 is an austenitic stainless whose defining ingredient is molybdenum — it's what lifts chloride/pitting resistance above 304. Nominal composition (balance iron):

Element	Content	Element	Content
Chromium (Cr)	16.0–18.0%	Manganese (Mn)	≤2.0%
Nickel (Ni)	10.0–14.0%	Silicon (Si)	≤0.75%
Molybdenum (Mo)	2.0–3.0%	Phosphorus (P)	≤0.045%
Carbon (C)	≤0.08% (316L ≤0.03%)	Sulphur (S)	≤0.030%

How We Machine 316

316 behaves like 304 but cuts a little harder and holds heat, so discipline matters even more:

Sharp, rigid tooling with positive feeds to stay under the work-hardened layer
Strong coolant to carry heat away and protect tool life
Tolerances: ±0.025 mm (±0.001 in) on critical features — verified on inspection
We avoid cross-contamination with carbon steel so the corrosion resistance isn't compromised

Tooling, Speeds & Feeds — Starting Points

Same golden rule as 304 — never let the tool dwell or rub — but 316 is more demanding: lower machinability (~36%), more heat retained, faster tool wear. Cut firmly, flood it, and keep tool engagement constant. Typical starting points (tuned per part):

Parameter	Typical for 316 / 316L
Tooling	Coated carbide — TiAlN / TiCN for heat & wear
Cutting speed	~50–70 m/min (165–230 SFM) carbide end mills — a touch below 304
Feed / chip load	0.15–0.35 mm/rev — positive & consistent, never trailing off
Depth of cut	Stay below the previously work-hardened layer each pass
Coolant	High-pressure flood — non-negotiable on 316
Golden rule	Tool always cutting — no dwell, no rubbing

Finishing 316

Passivation — essential after machining to restore the protective oxide layer
Electropolishing — bright, ultra-clean, easy-to-sterilise surface for medical/pharma
Bead blast / brushed — uniform decorative or matte finishes

316 vs 304 — Quick Comparison

	316	304
Molybdenum	2–3%	None
Chloride / pitting resistance	Excellent	Good
Marine / chemical / medical	Preferred	Limited
Machinability	~36%	~45%
Cost	Higher	Lower

No chloride exposure? 304 is the cheaper default. See all options on our materials overview.

Typical 316 Parts

Marine fittings, fasteners and deck hardware
Chemical and pharmaceutical process parts
Surgical and medical-device components
Food and beverage contact parts
Sensor and instrumentation fittings — e.g. our stainless fittings batch

Frequently Asked Questions

316's 2–3% molybdenum gives far better resistance to chlorides and pitting — essential for marine, salt, chemical and many medical parts. Without chloride exposure, 304 is more cost-effective.

316L has lower carbon (≤0.03%) to resist intergranular corrosion at welds — better for welded assemblies. Standard 316 has slightly higher strength for non-welded parts. We stock both.

Slightly — ~36% machinability vs ~45% for 304, and it work-hardens similarly. Sharp rigid tooling, positive feeds and good coolant give clean parts; it just runs slower.

Yes — it's a standard for surgical, pharma and food-contact parts. We passivate and can electropolish to a bright, hygienic surface.

316 / 316L Stainless Steel CNC Machining