Stainless Steel 316 CNC Machining Services
316 adds 2 to 3 percent molybdenum to the 304 base, roughly doubling resistance to chloride pitting and making it the default choice for marine, chemical and medical service.
316, 316L and 316Ti bar and plate
Tolerances to ±0.05 mm on critical features
Passivation and electropolishing available
What Is Stainless Steel 316?
Where 316 pays for itself, what molybdenum actually changes, and how it cuts compared with 304.
Stainless steel 316 is the molybdenum-bearing version of 304. Mechanically the two are nearly identical in the annealed condition, so the decision is almost never about strength: it is about the environment. The 2 to 3 percent molybdenum raises the pitting resistance equivalent number from about 19 to about 25, which is the difference between a fitting that pits in a season and one that lasts for years in salt air.
Where 316 is worth the premium
Specify 316 for seawater and coastal exposure, de-icing salt, brine and chlorinated process streams, acidic food production with clean-in-place systems, and for pharmaceutical and medical hardware that sees repeated chemical cleaning. For dry indoor atmospheres, fresh water and ordinary food products, 304 usually performs just as well at lower cost.
Machining behaviour
316 cuts similarly to 304 and work hardens in the same way, but it generates slightly higher cutting forces and more heat at the edge, so tool wear is a little faster. The same rules apply: keep the tool engaged, run a positive rake with a constant feed, use flood or high-pressure coolant, and never dwell. 316L is preferred where the part will be welded.
Related capabilities: CNC Machining, CNC Milling, CNC Turning, 5-Axis Machining. Dimensional limits, thread rules and surface roughness grades are listed on the tolerances and specifications page, and volume-based routing is covered under production solutions.
Stainless Steel 316 Mechanical Properties
Typical values at room temperature for the condition most often machined. Use them for material screening, then confirm against the mill certificate for the exact heat and product form.
| Property | Typical value |
|---|---|
| Density | 8.00 g/cm³ |
| Ultimate tensile strength | 515 MPa (75 ksi) minimum |
| Tensile yield strength, 0.2% offset | 205 MPa (30 ksi) minimum |
| Elongation at break | 40% minimum in 50 mm |
| Elastic modulus | 193 GPa |
| Hardness | 217 HB maximum (95 HRB) |
| Thermal conductivity | 16.3 W/m·K at 100 °C |
| Pitting resistance equivalent number | About 25, versus about 19 for 304 |
| Melting range | 1370 to 1400 °C |
| Magnetic response | Non-magnetic when annealed |
Typical room-temperature values compiled from public ASM, MatWeb and mill datasheets. Actual values vary with temper, section thickness and product form; request the EN 10204 3.1 certificate for critical applications.
Machining Characteristics of Stainless Steel 316
How the material behaves in the cut, and what that means for tooling, fixtures, cycle time and achievable tolerance.
Higher cutting forces
Expect roughly 10 percent more tool load than 304 and a shorter tool life. Rigid setups and premium carbide pay for themselves on 316.
Heat management
With only 16.3 W/m·K conductivity, heat concentrates at the cutting edge. High-pressure coolant through the tool is standard on deep pockets and holes.
Avoid rubbing
Austenitic 316 work hardens quickly. Constant feed and positive chip load are essential, especially on interrupted cuts and in corners.
Drilling strategy
Stub drills, pecking and sharp geometry. Work-hardened hole walls are the most common cause of broken taps on 316 parts.
Weld-friendly variants
316L keeps carbon below 0.03 percent and is the standard choice for welded assemblies that cannot be annealed afterwards.
Clean handling
Use dedicated stainless tooling and clean fixtures. Free iron contamination from carbon steel tooling causes rust spotting after passivation.
Design and Machining Checklist
Practical rules that reduce cost and scrap on Stainless Steel 316 parts. Share them with your design team before the drawing is frozen.
- Specify 316L for any welded assembly to avoid sensitisation and weld decay in the heat-affected zone.
- Passivate after machining; it is the cheapest insurance against rust spots on an expensive part.
- Use anti-galling compounds or dissimilar metals on threaded stainless pairings, which seize easily under load.
- Add generous radii instead of sharp internal corners; 316 work hardens fastest exactly where tools dwell.
- Do not assume 316 is immune to chlorides; at elevated temperature and high chloride concentration, duplex or super-austenitic grades may be required.
- Electropolish food and medical parts to remove embedded contaminants and reduce bacterial retention.
Surface Finishing Options
Finishes are selected for corrosion resistance, wear, appearance, electrical behaviour or cleanliness. Specify only what the function needs.
As-Machined
Ra 1.6 to 3.2 µm. Passivation is strongly recommended even for parts that stay indoors.
Passivation ASTM A967
Nitric or citric acid treatment that removes free iron and rebuilds the passive layer, the standard finish for corrosion-critical parts.
Electropolishing
Removes 5 to 40 µm of material, lowers Ra by around half, and produces a bright cleanable surface used in pharmaceutical and food plant.
Bead Blasting
Satin, non-directional finish for marine hardware and architectural components where glare must be avoided.
Mirror Polishing
Mechanical polish to Ra 0.05 µm for sanitary pipework, vessel interiors and decorative architectural elements.
PTFE or Ceramic Coating
Release and anti-galling coatings for threaded and sliding stainless components used in aggressive media.
Typical Applications
Where Stainless Steel 316 is most often specified, and why it wins against the alternatives.
Marine and offshore hardware
Deck fittings, propeller components, cleats, instrument housings and rigging hardware exposed continuously to salt spray.
Chemical and petrochemical processing
Valve bodies, pump components, manifolds and sampling systems handling chlorides and dilute acids.
Medical and pharmaceutical
Surgical instrument components, instrument housings, process contact parts and sterilisation trays.
Food and beverage processing
Tanks, fittings and pipework in acidic production lines and clean-in-place systems.
Coastal architecture
Balustrade posts, brackets and fixings on buildings within a few hundred metres of the sea.
Water treatment
Filter housings, flanges, diffusers and instrument fittings in chlorinated water systems.
Need Stainless Steel 316 parts quoted?
Upload your CAD files for a detailed quote on Stainless Steel 316 components, including material certification, finishing, inspection and worldwide delivery.