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When a worn or corroded bearing brings your project to a halt, finding an exact-fit replacement that won't fail again is the real challenge. Whether you're a maker rebuilding a skateboard, a technician servicing a pump, or an engineer sourcing precision components, these 440C stainless steel ball bearings deliver the dimensional accuracy and corrosion resistance your application demands.
Each bearing is manufactured from 440C martensitic stainless steel — one of the hardest stainless alloys available — and ground to G5 ABEC grade tolerances. Available diameters span 15.081 mm (~0.594") through 60 mm (~2.362"), covering both metric and inch-series sizes. The smooth, mirror-polished ball surface minimizes rolling friction and extends service life under load.
Typical use cases include replacing worn balls in deep-groove radial bearings for electric motors and fans, restoring smooth action in linear slides and drawer mechanisms, and sourcing precision balls for custom jigs, fixtures, and robotic joints where tight tolerances are non-negotiable.
| Material | 440C Martensitic Stainless Steel |
|---|---|
| Grade | G5 (ABEC / ISO 3290) |
| Diameter Range | 15.081 mm – 60 mm (approx. 0.594" – 2.362") |
| Surface Finish | Mirror-polished |
| Hardness | Typically 58–62 HRC (after heat treatment) |
| Corrosion Resistance | Good — suitable for humid and mildly corrosive environments |
| Pack Quantity | 1 piece per order (see variant options) |
| Weight | See variant options |
| Operating Temperature | Typically –20°C to +150°C (–4°F to +302°F) |
| Standards Compliance | ISO 3290 G5 / ABEC Grade 5 |
Measure the diameter of the existing balls in your bearing using a micrometer or digital caliper. Match that measurement to the closest available size in the variant selector. For inch-series bearings, note that common fractional sizes are included: 15.875 mm (5/8"), 19.05 mm (3/4"), 25.4 mm (1"), 31.75 mm (1-1/4"), 38.1 mm (1-1/2"), and 50.8 mm (2"). If your measurement falls between two listed sizes, always select the smaller size and confirm against your bearing manufacturer's specification sheet.
Load capacity depends on the full bearing assembly — the race geometry, number of balls, and housing — not the ball alone. However, 440C stainless steel at G5 grade provides high hardness (typically 58–62 HRC) and good fatigue resistance, making these balls suitable for moderate-to-heavy radial and thrust loads in standard bearing configurations. For critical load calculations, consult your bearing manufacturer's dynamic and static load ratings.
Yes. 440C stainless steel offers good corrosion resistance against moisture, rain, and mild atmospheric exposure, making it a reliable choice for outdoor equipment, marine-adjacent applications, and food-processing machinery where occasional water contact occurs. For highly aggressive chemical environments (strong acids, chlorinated water, or saltwater immersion), consider 316 stainless or ceramic alternatives, as 440C can pit under prolonged exposure to chlorides.
Grade numbers in ISO 3290 refer to the maximum allowable deviation in sphericity and diameter variation — a lower number means tighter tolerances. G5 balls have a maximum spherical deviation of 0.13 µm, making them suitable for precision instruments, high-speed spindles, and low-noise applications. G10 and G25 grades have progressively looser tolerances and are typically used in general-purpose or lower-speed bearings. For most DIY repair and replacement tasks, G5 provides more than adequate precision.
Yes, that is the primary use case. If your bearing races are undamaged but the balls show pitting, flat spots, or corrosion, replacing only the ball complement is a cost-effective repair. Carefully disassemble the bearing, clean the races, inspect for race damage, and install the new balls with a light application of appropriate bearing grease before reassembly. Ensure the replacement ball diameter exactly matches the original specification.
Yes. The size range includes both metric diameters (e.g., 15 mm, 16 mm, 20 mm, 25 mm, 30 mm) and inch-series equivalents expressed in millimeters (e.g., 15.875 mm = 5/8", 22.225 mm = 7/8", 25.4 mm = 1"). This makes them compatible with bearings manufactured to both ISO metric and ANSI/ABMA inch standards. Always verify the exact ball diameter from your bearing's datasheet rather than relying on nominal size alone.
Store balls in a clean, dry environment away from ferrous metal chips or abrasive particles that could scratch the polished surface. Keep them in their original packaging or a sealed container with a light coating of clean machine oil or VCI (vapor corrosion inhibitor) paper. Avoid stacking heavy objects on top of stored balls, as point-contact pressure can cause brinelling (small indentations) on the polished surface over time.
