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When standard carbon-steel bearings corrode, seize, or contaminate a process, engineers and maintenance professionals turn to AISI 316 stainless steel ball bearings. Whether you are rebuilding a saltwater pump, specifying components for a food-processing line, or sourcing replacements for chemical-handling equipment, finding a reliable metric-size bearing in the exact diameter you need — without minimum-order headaches — is the first obstacle. These 316 SS ball bearings are stocked in a continuous metric range from 3 mm to 38.1 mm (approximately 0.118 in to 1.500 in) and are available in quantities from a single piece to 1,000-piece bulk packs.
Each ball is manufactured from AISI 316 (equivalent to SUS 316 / 1.4401) austenitic stainless steel, which adds molybdenum to the alloy for enhanced resistance to chloride pitting compared with 304-grade material. Diameters span 3 mm, 3.5 mm, 4 mm, 5 mm, 6 mm, 6.35 mm (¼ in), 7 mm, 7.938 mm (5/16 in), 8 mm, 9 mm, and 38.1 mm (1½ in). Sphericity and surface finish are held to tight tolerances consistent with precision rolling-element standards, making these balls suitable for use in bearing assemblies, valves, and metering devices.
Typical applications include marine hardware and deck fittings exposed to seawater spray, pharmaceutical and food-grade conveyor bearings where hygiene and corrosion resistance are both required, and chemical-plant valve seats where molybdenum-bearing stainless outperforms standard grades. The 6.35 mm and 7.938 mm imperial-equivalent sizes also serve as direct replacements in legacy inch-dimension assemblies still common in North American industrial equipment.
Molybdenum addition provides measurably better chloride-pitting resistance than 304 SS, extending service life in marine and chemical environments.
Eleven diameters from 3 mm to 38.1 mm — including imperial-equivalent 6.35 mm (¼ in) and 7.938 mm (5/16 in) — cover the majority of metric and legacy inch-dimension applications.
Tight roundness and surface-finish tolerances ensure consistent load distribution and low noise in bearing assemblies, valves, and flow-control devices.
316 SS is essentially non-magnetic in the annealed condition, making these balls suitable for MRI-adjacent equipment and sensitive instrumentation.
Order from 1 piece for a single repair up to 1,000 pieces for production runs — no forced bulk commitment on smaller diameters.
Sized to standard metric and inch-equivalent nominal dimensions, these balls drop into existing housings without modification in most applications.
| Material Grade | AISI 316 (SUS 316 / 1.4401) Austenitic Stainless Steel |
|---|---|
| Alloying Elements | Iron, Chromium (~16–18%), Nickel (~10–14%), Molybdenum (~2–3%) |
| Diameter Range | 3 mm – 38.1 mm (0.118 in – 1.500 in) |
| Available Diameters | 3, 3.5, 4, 5, 6, 6.35, 7, 7.938, 8, 9, 38.1 mm |
| Imperial Equivalents | 6.35 mm = ¼ in; 7.938 mm = 5/16 in; 38.1 mm = 1½ in |
| Surface Finish | See variant options |
| Sphericity Grade | See variant options |
| Magnetic Properties | Essentially non-magnetic (austenitic, annealed condition) |
| Corrosion Resistance | Resistant to chlorides, mild acids, and marine atmospheres |
| Pack Quantities | 1, 2, 5, 10, 25, 50, 100, 200, 300, 500, 1000 pcs |
| Weight per Unit | See variant options |
Measure the existing ball with a micrometer or refer to the bearing manufacturer's part number, which typically encodes the ball diameter. For valve seats, the seat drawing will specify the nominal ball diameter and the required sphericity grade. Match the nominal dimension exactly — even a 0.5 mm difference will affect fit and load rating.
AISI 316 contains 2–3% molybdenum, which significantly improves resistance to chloride-induced pitting corrosion. In marine, coastal, food-processing, and chemical environments where chloride ions are present, 316 SS maintains its surface integrity far longer than 304 SS, reducing the risk of bearing failure or contamination.
AISI 316 stainless steel is widely accepted in food-contact and pharmaceutical equipment due to its corrosion resistance and ease of cleaning. However, compliance with specific regulatory standards (e.g., FDA, EU 10/2011) depends on the full assembly design and any lubricants used. Confirm with your compliance team before specifying for regulated applications.
6.35 mm is the metric expression of ¼ inch (exact conversion: 6.350 mm), and 7.938 mm equals 5/16 inch (exact: 7.9375 mm). These sizes are stocked to serve legacy inch-dimension assemblies common in North American industrial equipment. If your drawing calls for ¼ in or 5/16 in balls, select the corresponding metric listing — the dimensions are interchangeable.
Yes. AISI 316 is one of the most common stainless grades specified for marine hardware precisely because molybdenum improves resistance to seawater and salt-spray corrosion. For fully submerged or high-velocity seawater applications, consider pairing with a compatible 316 SS housing and a marine-grade lubricant to maximize service life.
Store in a dry, clean environment away from dissimilar metals to prevent galvanic contact corrosion. Keep in the original packaging or a sealed container to avoid surface contamination. Avoid contact with carbon-steel tools or surfaces during handling, as embedded iron particles can cause surface rust spots even on stainless steel.
For single repairs or prototyping, the 1- or 10-piece packs minimize upfront cost. For scheduled maintenance programs, the 100- or 200-piece packs offer a lower per-unit price while keeping inventory manageable. Production runs or high-volume stocking are best served by the 500- or 1,000-piece options, which provide the lowest per-ball cost across the range.
