3.0mm-3.965mm SINGLE STEEL BALL BEARINGS G10 HIGH PRECISION CARBON STEEL BALL

Measure the inner diameter of your bearing housing (bore) and the diameter of the existing balls with a micrometer. The replacement ball should match the original diameter as closely as possible. If you are adjusting preload, select a ball 0.002–0.005 mm larger than the worn ball to restore proper fit. Use the incremental sizes in this listing to dial in the exact dimension you need.

G10 is an ABMA/ISO precision grade indicating that the ball's diameter deviation and roundness error are each within 0.0025 mm (2.5 microns). This is a general-purpose precision grade suitable for most tool, instrument, and light industrial applications. Higher grades (G5, G3) offer tighter tolerances but are typically only needed in ultra-precision spindles or measuring instruments.

Carbon steel balls are not inherently corrosion-resistant. For wet, humid, or chemically exposed environments, stainless steel balls (AISI 440C or 316) are recommended instead. If you must use carbon steel in a mildly damp environment, apply a light coat of oil or grease and replace the balls more frequently as part of your maintenance schedule.

Yes. Many skateboard and inline skate bearings use balls in the 3 mm–4 mm range. If your bearing is noisy or rough due to worn or pitted balls, you can replace just the ball complement. Measure the existing balls carefully — even a 0.01 mm difference can affect preload and noise. Select the diameter that matches or is 0.002–0.003 mm larger than the worn balls to restore smooth rolling.

For a single bearing repair, a pack of 10–20 is usually sufficient (most small bearings use 7–12 balls per complement). For workshop stock or small production runs, packs of 100–300 offer a better per-unit cost. For high-volume production or resale, the 500 or 1,000-piece packs provide the lowest per-ball price. Check the pricing tiers shown in the variant selector above.

Disassemble the bearing carefully and count the existing balls, or refer to the bearing manufacturer's datasheet using the bearing part number. If the datasheet is unavailable, a general rule for radial ball bearings is that the ball complement is approximately 60–70% of the maximum number of balls that could fit in the raceway. Contact us to confirm if you are unsure.

No, these balls are supplied clean and unlubricated. Apply your preferred bearing grease or oil during assembly. For high-speed applications, a light spindle oil is recommended. For slower, higher-load applications, a lithium-based or synthetic grease provides better film strength and longer service intervals.