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When worn or undersized balls cause vibration, noise, or premature bearing failure, the root cause is almost always dimensional inconsistency or inadequate corrosion resistance. Engineers, machinists, and serious DIYers who need 440C stainless steel bearing balls that hold tight tolerances across the full size range will find exactly what they need here — available from 1.5 mm (0.059 in) up to 95.25 mm (3.750 in) in a single listing.
Each ball is manufactured from 440C martensitic stainless steel, hardened and ground to ABEC / ISO Grade 10 tolerances. The spherical form deviation is held to ≤0.25 µm at Grade 10, delivering a surface finish that supports low-friction, low-noise operation. Diameters span the full metric and inch series — including fractional inch sizes such as 1/16", 3/32", 5/32", 7/32", 9/32", 11/32", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 1", 1-1/16", 1-1/8", 1-3/16", 1-1/4", 1-3/8", 1-1/2", 2", 2-1/4", 2-3/4", and 3-3/4" — alongside standard metric sizes.
Typical use cases include replacement balls in deep-groove and angular-contact bearings for pumps, conveyors, and machine tool spindles; check-valve seats in fluid-handling systems exposed to mild acids or salt spray; precision pivot points in optical and measuring instruments; and load-distributing elements in linear guides and ball screws used in CNC and 3D-printing equipment.
| Material | 440C Martensitic Stainless Steel |
|---|---|
| Grade | Grade 10 (ISO 3290 / ABEC equivalent) |
| Diameter Range | 1.5 mm – 95.25 mm (0.059 in – 3.750 in) |
| Hardness | Typically 58–62 HRC (after heat treatment) |
| Spherical Form Deviation | ≤ 0.25 µm (Grade 10) |
| Surface Roughness (Ra) | ≤ 0.025 µm |
| Chromium Content | 16–18% |
| Finish | Bright ground, smooth |
| Pack Size Options | 1 / 10 / 20 / 50 / 100 / 200 / 500 / 1000 Pcs |
| Diameter (select) | See variant options |
| Weight per Ball | See variant options |
| Operating Temperature | Typically –60°C to +200°C (–76°F to +392°F) |
| Magnetic | Slightly magnetic (martensitic grade) |
Measure the inner diameter of the bearing race pocket using a calibrated micrometer or ball gauge. The replacement ball should match the original diameter within the bearing's specified tolerance. If you have the bearing part number, cross-reference the manufacturer's datasheet for the ball complement diameter. When in doubt, order one piece first to verify fit before purchasing a larger pack.
Grade number refers to the maximum allowable spherical form deviation in units of 0.025 µm (0.000001 in). Grade 10 allows ≤0.25 µm deviation — suitable for most industrial bearings, pumps, and precision DIY applications. Grade 25 (≤0.625 µm) and Grade 100 (≤2.5 µm) are less precise and used in lower-speed or lower-load applications. For high-speed spindles or precision instruments, Grade 10 is the appropriate choice.
440C offers good corrosion resistance in mild environments — including fresh water, salt spray, and dilute acids — due to its 16–18% chromium content. However, it is not fully immune to corrosion in concentrated chloride solutions or strong oxidizing acids. For highly aggressive chemical environments, 316L stainless or ceramic balls may be more appropriate. For most outdoor, marine, and food-adjacent applications, 440C performs reliably.
Yes. The size range includes both metric diameters (e.g., 1.5 mm, 2 mm, 3 mm … 95.25 mm) and fractional-inch equivalents (e.g., 1.588 mm = 1/16", 6.35 mm = 1/4", 25.4 mm = 1"). Select the diameter that matches your bearing's ball complement specification. The balls are dimensionally interchangeable with standard bearing races of the same nominal diameter.
Yes. 440C stainless steel balls are widely used as check-valve seats in hydraulic, pneumatic, and water-handling systems. The hardened surface resists deformation under repeated seating impacts, and the corrosion resistance is adequate for most process fluids. Verify chemical compatibility with your specific fluid before installation, particularly for strong acids or halogens.
For a single bearing replacement, the 1-piece or 10-piece pack is most economical. If you are servicing multiple bearings of the same size, the 50- or 100-piece pack reduces per-unit cost significantly. Production environments or maintenance departments that regularly stock consumables will find the 500- or 1000-piece packs offer the best value and reduce reorder frequency.
Martensitic stainless steels like 440C are slightly magnetic due to their crystal structure. In most bearing and valve applications this is not an issue. However, if your application requires non-magnetic balls — such as in MRI equipment, sensitive electronic assemblies, or certain laboratory instruments — consider 316L stainless or silicon nitride ceramic balls instead.
