316 / A4 Stainless Steel Fasteners
The saltwater stainless — for boats, docks, coastal structures, and chemical exposure. Quoted per order, confirmed before you pay.
Why 316?
316 stainless steel contains molybdenum, which gives it substantially better resistance to pitting and crevice corrosion in saltwater and high-humidity conditions than 304 or 18-8 stainless. That is why 316 is the default choice for offshore hardware, professional shipyards, and demanding coastal environments. A4 is the metric designation for the same 316 alloy family — if you see A4-70 or A4-80, you are looking at metric 316.
316L is the low-carbon variant of 316. Its lower carbon content reduces carbide precipitation during welding, which makes it the better choice where the fastener will be welded or exposed to heat. If your job involves welding, say so in your quote request.
316 is not the right answer for everything. It is softer than some alloy steels, it can gall (threads seizing) if over-torqued dry, and it is the wrong choice where a job genuinely requires certified material or lot traceability — we do not claim certifications we do not hold, and we will tell you if your job needs a certified supplier instead.
Fastener families in 316
- Hex bolts and hex cap screws — the general-purpose structural fastener, with a nut or into a tapped hole. Partial-thread and full-thread patterns available by quote.
- Machine screws — smaller diameters for machinery, panels, and assemblies, in slotted, Phillips, and hex-socket drives.
- Nuts — hex finish nuts, nylon-insert lock nuts, and jam nuts to match your bolt thread.
- Washers — flat washers, lock washers, and finish washers in matching 316.
- Threaded rod — continuous thread for hangers, tie rods, and custom-length studs, cut to your length at quote.
Related family: silicon bronze fasteners for wooden boats and non-magnetic work.
How to specify a 316 fastener
Your quote moves fastest when you give all of these. If you are unsure of one field, describe the job and we will confirm the specification with you before anything is quoted.
| Field | Example (inch) | Example (metric) |
|---|---|---|
| Material | 316 | 316 / A4 |
| Fastener type | Hex bolt | Hex bolt, DIN 933 |
| Diameter | 5/16 inch | M8 |
| Thread | 18 threads per inch | 1.25 mm pitch |
| Length | 1 inch | 20 mm |
| Head / drive | Hex head, external hex | Hex head, external hex |
| Quantity | 12 pieces | 50 pieces |
Metric 316 — the hard-to-find sub-line
Metric 316/A4 sizes are often underserved in the U.S. market, and they are a standing sub-line of this store — not a separate shop. Common patterns include hex bolts to DIN 931 (partial thread) and DIN 933 (full thread), in diameters from M4 upward. The classic metric mistake is pitch: an M8 bolt can be 1.25 mm coarse pitch or 1.0 mm fine pitch, and the two do not interchange. Always give pitch with diameter, and your quote will confirm that exact combination — never an inch substitute.
Applications
- Boats, docks, and marinas — hardware in constant saltwater contact.
- Coastal structures, railings, and outdoor fixtures in salt air.
- Chemical and food-adjacent environments where corrosion resistance matters.
- Restoration work matching original stainless hardware.
Common questions
What is the difference between 316 and 304?
316 contains molybdenum, giving it substantially better resistance to pitting and crevice corrosion in saltwater than 304 or 18-8. For freshwater or indoor use, 304 is often adequate; for saltwater, 316 is the standard choice.
Do you sell metric 316?
Yes — metric 316/A4 is a sub-line of this store. Give diameter, pitch, and length exactly.
Is anything on this page in stock?
No. Every order is sourced to your exact specification and confirmed before payment. Nothing here is a stock list.
How much does a 316 bolt cost?
Prices are quoted per order against current supplier availability for your exact specification. Request a quote and you will get a written price before you pay anything.