Metric Sizes Shielded

Miniature and Small Metric-Size Bearings – Shielded are precision rolling bearings manufactured to metric dimensions, equipped with metal shields (ZZ or Z configuration) on one or both sides. These shields provide effective protection against larger contaminant particles while maintaining low friction and high-speed capability. Bore diameters typically range from 3 mm to 12 mm, with outer diameters from 8 mm to 28 mm.

Key Technical Features:

• Shield design: Non-contact metal shields (typically pressed steel or stainless steel) are crimped into a groove on the outer ring. A narrow annular gap (typically 0.05–0.15 mm) between the shield and inner ring allows minimal friction while blocking airborne dust, fibers, and larger debris.

• Metric size standards: Conforming to ISO 15 and DIN 625 dimensions. Common shielded series include 60ZZ (e.g., 608ZZ: 8×22×7 mm), 62ZZ (e.g., 626ZZ: 6×19×6 mm), 63ZZ (e.g., 623ZZ: 3×10×4 mm), and 69ZZ (e.g., 696ZZ: 6×15×5 mm). ZZ indicates double shields; Z indicates single shield.

• Precision grades: Available from P0 (ABEC 1) for general use to P5 (ABEC 5) for higher precision requirements. Shielded miniature metric bearings routinely achieve P5 tolerances in premium grades.

• Materials: Chrome steel (52100) rings and balls (Grade 5 or 10) for standard applications; stainless steel (440C) for corrosion resistance; hybrid ceramic (Si₃N₄ balls) for electrical insulation or extreme speeds.

• Lubrication: Pre-lubricated at factory with high-quality grease (typically lithium-based or synthetic) selected for low torque, wide temperature range (-40°C to +120°C), and long life. Shields retain grease effectively while preventing contamination ingress.

• Torque characteristics: Shielded bearings exhibit slightly higher starting and running torque than open bearings due to grease drag, but significantly lower than sealed versions. Typical torque values range from 0.5–5 g·cm depending on size and grease fill.

• Speed capability: Non-contact shields allow speeds comparable to open bearings (up to 40,000–50,000 RPM for smaller sizes), limited primarily by grease and cage design rather than shield drag.

• Cage options: Crown-type (ribbon) cages in steel, phenolic resin, or polyamide optimize ball spacing and reduce friction.

• Environmental protection: Shields provide protection against dry, fibrous, or larger-particle contamination (typically >50 microns). Not suitable for wet environments or fine dust (use sealed versions instead).

• Maintenance: Shielded bearings are generally non-relubricatable (no grease fittings) and designed for "lubricated-for-life" service in clean to moderately clean environments.

Applications:
Shielded miniature metric bearings are ideal for small electric motors, cooling fans, office automation equipment (printers, scanners, copiers), computer hard disk drives, precision pumps, dental handpieces, model aircraft engines, radio-controlled vehicles, instrumentation, and robotics joints. They provide an optimal balance of contamination protection, low friction, and high-speed performance in compact metric assemblies.