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When a worn or undersized ball bearing causes play, noise, or premature failure in a bearing assembly, finding the exact replacement diameter is the real challenge. Machinists, maintenance technicians, and serious DIYers who work across both metric and imperial systems know that a 0.1mm mismatch is enough to compromise a whole assembly. These steel ball bearings are stocked in 45 discrete sizes to eliminate that guesswork.
Each ball is manufactured from hardened carbon steel, delivering the surface hardness and dimensional consistency required for load-bearing rolling contact. Sizes span 7.938mm (5/16 in) through 21.431mm (27/32 in), covering the most common metric steps as well as fractional-inch equivalents such as 9.525mm (3/8 in), 12.7mm (1/2 in), 15.875mm (5/8 in), 19.05mm (3/4 in), and 19.844mm (25/32 in). Available in packs of 10, 20, or 50 pieces to match your project volume.
Typical use cases include replacing rolling elements in deep-groove ball bearings, angular contact bearings, and thrust bearing assemblies; restoring smooth action in drawer slides, caster wheels, and bicycle hubs; and serving as precision spacers or load-transfer elements in custom jigs, fixtures, and mechanical linkages where exact diameter control is critical.
Covers 7.938mm to 21.431mm in metric steps and fractional-inch equivalents, so you can match the exact diameter your assembly requires without compromise.
Manufactured from hardened carbon steel for the surface hardness needed to withstand rolling contact loads, resist deformation, and maintain dimensional accuracy over service life.
Includes both clean metric steps (8mm, 10mm, 12mm, 15mm, 20mm) and fractional-inch sizes (9.525mm = 3/8", 12.7mm = 1/2", 15.875mm = 5/8", 19.05mm = 3/4") for cross-system compatibility.
Choose from packs of 10, 20, or 50 pieces per size. Order a small quantity for a single repair or stock up in bulk for ongoing maintenance and production runs.
Uniform spherical form ensures even load distribution across the contact zone, reducing point stress and extending the service life of the surrounding race and housing.
Suitable for deep-groove bearings, thrust assemblies, caster wheels, bicycle hubs, drawer slides, and custom mechanical fixtures where precise rolling-element diameter is required.
| Material | Hardened carbon steel |
|---|---|
| Diameter Range | 7.938mm – 21.431mm (approx. 5/16" – 27/32") |
| Available Sizes | 45 sizes (metric steps + fractional-inch equivalents) |
| Pack Quantities | 10 pcs / 20 pcs / 50 pcs |
| Surface Finish | See variant options |
| Hardness | See variant options |
| Grade / Tolerance | See variant options |
| Weight per Ball | See variant options |
| Application Type | Replacement rolling elements; precision mechanical assemblies |
| Compatible Bearing Types | Deep-groove, angular contact, thrust bearings; casters; hubs |
Remove one ball from the existing bearing race and measure its diameter with a micrometer or digital caliper. Match that measurement to the closest size in the variant selector. For fractional-inch bearings, use the imperial equivalents listed in the product description (e.g., 12.7mm = 1/2", 15.875mm = 5/8"). If your measurement falls between two listed sizes, contact us to confirm before ordering.
Load capacity depends on ball diameter, the hardness of the mating race, and the application's speed and lubrication conditions. Larger-diameter balls distribute load over a greater contact area and generally support higher radial loads. For critical load calculations, refer to the bearing manufacturer's specification sheet for your specific race and housing. These balls are intended as replacement rolling elements in standard bearing assemblies.
These balls are manufactured from hardened carbon steel, which provides excellent hardness and load-bearing performance but has limited inherent corrosion resistance compared to stainless steel. For applications exposed to moisture, mild chemicals, or outdoor environments, apply a compatible bearing grease or lubricant to protect the surface. If your application requires stainless steel balls, contact us to confirm availability.
Yes. The range includes clean metric steps (8mm, 9mm, 10mm, 12mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm) alongside fractional-inch equivalents such as 7.938mm (5/16"), 9.525mm (3/8"), 11.113mm (7/16"), 12.7mm (1/2"), 14.288mm (9/16"), 15.875mm (5/8"), 17.463mm (11/16"), 19.05mm (3/4"), 19.844mm (25/32"), and 21.431mm (27/32"). Select the size that matches your existing ball or race specification.
Yes. Steel ball bearings in this size range are commonly used in bicycle cup-and-cone hubs, caster wheel assemblies, and drawer slide mechanisms. Measure the existing balls before ordering to confirm the diameter. For bicycle hubs, common sizes include 3/16" (4.763mm — not in this range), 1/4" (6.35mm — not in this range), and 5/16" (7.938mm) through 3/8" (9.525mm), which are covered here. Always verify your specific hub specification.
Choose based on your application volume. A pack of 10 suits a single bearing replacement where you need a few spares. A pack of 20 is practical for servicing multiple bearings of the same size in one session. A pack of 50 is cost-effective for production environments, maintenance stock, or applications where balls are replaced on a regular schedule. Larger packs offer a lower per-piece cost.
Store unused balls in a dry, covered container away from moisture and direct contact with dissimilar metals to prevent surface oxidation. A light coating of machine oil or bearing grease on stored balls will extend their shelf life. Keep them in their original packaging or a labeled parts bin sorted by diameter to avoid mixing sizes.
