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When a single undersized or rough-surfaced ball causes bearing failure, valve leakage, or measurement error, the cost of downtime far outweighs the cost of the part. Engineers, machinists, and serious DIYers who need dimensionally consistent, corrosion-resistant balls in exact diameters — from micro 0.4 mm to large 38.1 mm — need a reliable source they can order from in any quantity.
These 440C stainless steel precision balls are manufactured to G10 grade tolerances, meaning diameter variation is held to ±0.000025" (0.000635 mm) or better. The material is 440C martensitic stainless steel — a high-carbon, chromium-bearing alloy that delivers a hardness of approximately 58–62 HRC after heat treatment. Available diameters span 0.4 mm (0.016") through 31.75 mm (1.25"), with pack sizes from a single piece up to 1,000 pieces to suit prototyping through production runs.
Typical applications include radial and angular-contact ball bearings, check valves and ball valves, precision gauging and calibration fixtures, linear motion guides, pump components, and decorative or functional metalworking projects requiring a polished stainless sphere.
Diameter tolerance held to ±0.000025" (0.635 µm), ensuring consistent fit in bearing races, valve seats, and gauging fixtures without selective assembly.
High-carbon, high-chromium martensitic stainless steel with approximately 58–62 HRC hardness after heat treatment — resistant to wear, fatigue, and moderate corrosion.
The chromium content forms a passive oxide layer that resists rust in humid, mildly acidic, and salt-spray environments, extending service life in exposed assemblies.
20 distinct diameters from 0.4 mm (0.016") to 31.75 mm (1.25"), covering metric, fractional-inch, and wire-gauge sizes for both standard and custom applications.
Order 1, 2, 5, 10, 20, 50, 100, 500, or 1,000 pieces — scale from a single replacement ball to a full production batch without minimum-order constraints.
Bright-polished finish reduces friction and noise in rolling-element assemblies, and provides an aesthetically clean surface for decorative metalwork and display pieces.
| Material | 440C Martensitic Stainless Steel |
|---|---|
| Grade | G10 |
| Diameter Range | 0.4 mm – 31.75 mm (0.016" – 1.25") |
| Available Diameters | 0.4, 2, 2.5, 3, 4, 5, 6, 6.35, 7.144, 7.938, 8.731, 10, 11.1125, 12, 12.7, 14, 15.875, 20, 25, 31.75 mm |
| Diameter Tolerance (G10) | ±0.000025" (±0.635 µm) |
| Surface Finish | Bright polished |
| Hardness (approx.) | 58–62 HRC (after heat treatment) |
| Chromium Content | 16–18% |
| Carbon Content | 0.95–1.20% |
| Pack Sizes Available | 1, 2, 5, 10, 20, 50, 100, 500, 1000 Pcs |
| Weight per Unit | See variant options |
| Magnetism | Slightly magnetic (martensitic grade) |
| Temperature Range | See variant options |
Match the ball diameter to the bore specification of your bearing race or valve seat. For standard bearings, the ball diameter is listed in the bearing's datasheet (e.g., 6mm balls for a 6001 bearing). For valve seats, measure the seat bore with a caliper and select the closest listed diameter. When in doubt, contact us to confirm before ordering.
G10 is an ABMA/ISO precision grade indicating a diameter tolerance of ±0.000025" (0.635 µm) and a sphericity deviation of no more than 0.000025". This is suitable for most industrial bearings, check valves, and precision gauging. Applications requiring tighter tolerances (G5 or G3) should specify accordingly.
440C stainless steel achieves approximately 58–62 HRC hardness after heat treatment, giving it excellent compressive strength and fatigue resistance. These balls are used in rolling-element bearings that routinely handle thousands of pounds of dynamic load. Avoid impact loading or use in applications exceeding the rated dynamic capacity of the bearing assembly.
440C stainless steel forms a passive chromium-oxide layer that resists rust in humid air, mild acids, and salt-spray environments. However, it is not fully immune to corrosion in chloride-rich or strongly acidic environments. For marine or chemical-process applications, consider 316 stainless or ceramic alternatives. For most workshop, automotive, and general industrial use, 440C performs reliably.
440C stainless steel is used in some food-processing and medical equipment, but regulatory compliance depends on your specific application and jurisdiction. These balls are not supplied with FDA or medical-device certifications. If compliance documentation is required, please contact us before ordering.
Each variant is a specific combination of diameter and pack size — for example, 6 mm × 100 Pcs or 10 mm × 10 Pcs. You can add multiple variants to your cart to mix diameters and quantities in a single order. Larger pack sizes offer a lower per-piece cost, making them economical for production runs or stocking spare parts.
Yes, 440C is a martensitic stainless steel and is slightly magnetic after heat treatment. If your application requires non-magnetic balls (e.g., near sensitive electronics or MRI-adjacent equipment), consider austenitic stainless (316) or ceramic (Si3N4) alternatives.
