Precision 420 Stainless Steel Ball Bearing Replacement Bearings 0.4mm to 1mm

Measure the worn or missing ball with a micrometer or digital caliper. Match the measured diameter to the closest available size in this listing. For bearing races, the ball diameter must match the original specification — even a 0.1 mm difference can cause excessive play or binding. If you have the original bearing part number, cross-reference it to confirm the ball diameter before ordering.

420 stainless steel is a martensitic alloy that can be hardened to a useful level for many bearing applications. It is commonly used in valve balls, instrument bearings, and light-duty radial bearings. For heavy-load or high-speed precision bearings, grades such as 440C stainless or chrome steel (52100) offer higher hardness. Contact us to confirm suitability if your application involves significant radial or axial loads.

420 stainless steel provides moderate corrosion resistance — significantly better than carbon steel, but less than 316 stainless. These balls are suitable for humid workshop conditions, light mist, and incidental water contact. For continuous immersion in water, salt spray, or chemical exposure, consider 316 stainless or ceramic balls instead.

The diameters listed correspond to common metric and fractional-inch ball sizes used in standard miniature bearing races. However, bearing manufacturers specify ball grade (G10, G25, etc.) in addition to diameter. If your application requires a specific grade tolerance, contact us to confirm before ordering, as grade affects roundness and surface finish precision.

Both packs contain the same 420 stainless steel balls at the same diameter. The 500-piece pack offers a lower per-unit cost and is suited for production runs, bulk stocking, or workshops that regularly replace bearing balls. The 100-piece pack is a practical choice for single repairs or low-volume use where storing large quantities is not necessary.

420 stainless steel is not typically certified for food-contact or medical-grade applications. For those environments, 316L stainless or certified medical-grade materials are the appropriate choice. If you are unsure whether these balls meet your regulatory requirements, consult the relevant standards (e.g., FDA, ISO 10993) and contact us to confirm material documentation availability.

Several diameters in this listing correspond to fractional-inch standards: 1.5875 mm = 1/16 in, 2.381 mm = 3/32 in, 2.778 mm = 7/64 in, 3.969 mm = 5/32 in, 4.763 mm = 3/16 in, 5.556 mm = 7/32 in, 5.953 mm = 15/64 in, and 6.35 mm = 1/4 in. If your equipment was designed to inch standards, match the fractional equivalent rather than rounding to the nearest metric size.