Overview
ISO 3290-2:2014 - Rolling bearings - Balls - Part 2: Ceramic balls specifies the requirements for finished silicon nitride balls used in rolling bearings. The standard defines dimensional, form and surface quality, sorting and gauge systems, and material references needed for manufacturing, inspection and procurement of ceramic bearing balls.
Key topics and technical requirements
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Scope and material
- Applies to finished silicon nitride balls for rolling bearings. Material requirements reference ISO 26602.
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Definitions and symbols
- Defines key terms such as ball grade, ball gauge, mean ball diameter, deviation from spherical form, and other measurement symbols (see ISO 15241).
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Geometry and surface quality
- Specifies limits for:
- Variation of ball diameter (V)
- Deviation from spherical form (Δ)
- Surface roughness (Ra) - measured per ISO 4288
- Surface defects and waviness are discussed; limits and measuring methods for waviness and some local defects are subject to supplier–customer agreement.
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Dimensions, tolerances and nominal diameters
- Lists preferred nominal diameters (metric and corresponding inch sizes) and provides guidance on shortened identification formats for purchasing versus manufacturing.
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Sorting accuracy and ball gauges
- Establishes ball-gauge intervals, preferred gauges and subgauge practice to control lot mean diameter and variation.
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Normative annexes
- Annex A: method to assess deviation from spherical form
- Annex B: illustrations of ball gauges and sorting principles
- Annex C: examples of defect types and inspection methods
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Form and surface roughness tolerances (selected)
- Ball grades and maximum tolerances (micrometres):
- G 3: V = 0.08, Δ = 0.08, Ra = 0.01
- G 5: V = 0.13, Δ = 0.13, Ra = 0.014
- G 10: V = 0.25, Δ = 0.25, Ra = 0.02
- G 16: V = 0.40, Δ = 0.40, Ra = 0.025
- G 20: V = 0.50, Δ = 0.50, Ra = 0.032
- ... up to G 100: V = 2.5, Δ = 2.5, Ra = 0.10
Practical applications and who uses this standard
- Manufacturers of ceramic rolling bearing balls use ISO 3290-2 for production tolerances, sorting and inspection criteria.
- Bearing OEMs and designers reference it when specifying silicon nitride balls for assemblies requiring tight geometric control.
- Quality engineers and metrology labs rely on the standard for acceptance testing, surface-roughness measurement and lot-gauging procedures.
- Procurement and supply-chain professionals use the nominal-diameter and gauge conventions for unambiguous ordering.
Ceramic (silicon nitride) balls are commonly selected where high precision, low density and specific performance properties are needed; this standard ensures consistent, verifiable dimensional and surface-quality criteria for such applications.
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