20-30mm Diameter Bearing Steel Ball-Steel Solid Ball Bearings High Precision

Measure the bore or seat diameter of your existing bearing housing or valve body using a caliper. The ball should match that dimension within the specified clearance for your application. For replacement bearings, the original equipment specification or a worn ball's measured diameter (accounting for wear) is your starting point. This listing covers 20.5mm to 30mm in 32 distinct sizes, including common inch-derived sizes.

Bearing steel balls are commonly used as valve seats in low-to-medium pressure fluid systems where a hard, smooth spherical surface is needed to form a seal. However, bearing steel is not inherently corrosion-resistant in aggressive media (acids, saltwater). For corrosive environments, consider stainless steel balls instead. If your application involves water or light oils, bearing steel typically performs well with appropriate sealing.

Bearing steel balls made from GCr15 / 52100 grade steel are typically hardened to 60–66 HRC through heat treatment. This hardness level is standard for rolling element bearings and provides excellent resistance to surface fatigue, indentation, and wear under cyclic loading. Exact hardness values for a specific batch can be confirmed by contacting us.

Yes, provided the diameter matches the original ball size specified for that bearing. Standard bearing balls are graded by precision (G10, G16, G25, etc. per ISO 3290). For critical bearing rebuilds, confirm the grade requirement of your bearing. For general-purpose repairs, jigs, or fixtures, these balls are suitable. Always replace all balls in a bearing set simultaneously to maintain load distribution.

High-carbon chromium bearing steel has moderate corrosion resistance — it will develop surface rust if exposed to moisture without lubrication or protective coating. For dry indoor applications or lubricated assemblies, this is generally not a concern. For outdoor, wet, or chemically aggressive environments, stainless steel balls are a better choice. Applying a light oil film during storage and installation extends service life.

The number depends on your application. A single valve seat or gauge application typically needs 1 ball. A ball transfer unit may use 1 large ball plus several smaller retaining balls. A custom linear slide or bearing housing rebuild may require 4–20 balls depending on the track length and load. Use the Pack Quantity selector to choose the right count — options include 1, 2, 3, 4, 5, 8, 10, 15, or 20 pieces depending on the diameter selected.

Yes. Several diameters in this listing correspond to standard inch fractions: 25.4mm = 1 inch, 28.575mm = 1-1/8 inch, 22.225mm = 7/8 inch, 23.813mm = 15/16 inch, and 20.638mm ≈ 13/16 inch. These are useful when replacing balls in equipment originally specified in imperial dimensions. Select the diameter that matches your measurement.