628-2Z (628ZZ) is a miniature single-row deep groove ball bearing with an 8 mm bore diameter and 24 mm outside diameter. It features double-sided metal shields with a non-contact shielding design that effectively helps prevent dust and debris from entering the bearing while maintaining very low friction. Its limiting speed can reach up to 32,000 rpm. The bearing is factory pre-lubricated with grease and generally requires no additional lubrication under normal operating conditions. It provides low noise and smooth running performance. With standard metric dimensions, it is a direct replacement for the former model 80028 and is widely used in motors, household appliances, 3D printers, and various compact precision rotating mechanisms.
Product Advantages
Bidirectional Load Capacity: Primarily designed to accommodate radial loads while also supporting relatively small axial loads in both directions, providing good versatility for general applications.
Double-Sided 2Z Metal Shields: The non-contact metal shields provide dust protection while generating less friction than 2RS contact rubber seals, allowing higher operating speeds. They help prevent dust and debris from entering the bearing interior. The bearing is factory pre-greased and generally requires no additional lubrication; the sealed-shield configuration is not intended for grease replenishment.
Low Friction, Low Noise, and Low Vibration: The bearing supports stable, smooth operation and is suitable for high-speed rotating applications where low running resistance and controlled noise are required.
Simple Installation: Its standard metric dimensions provide convenient installation and good interchangeability, allowing use with equivalent bearings from different domestic and international manufacturers.
Compact and Lightweight Construction: The small overall dimensions and lightweight design make it suitable for equipment with limited installation space.
Application Limitation: The 2Z configuration primarily provides protection against dust and is not designed for water protection or high-pressure washing. For humid or water-exposed environments, the 628-2RS rubber-sealed version is generally more suitable.
Model Variants
628-2Z / 628ZZ: Double-sided metal shields; the most commonly used configuration.
628-Z / 628Z: Single-sided metal shield.
628-2RS: Double-sided contact rubber seals providing improved water and dust protection, with a lower limiting speed of approximately 18,000 rpm.
W628-2Z: Stainless steel corrosion-resistant version, suitable for humid or mildly corrosive environments.
Typical Applications
As a miniature bearing with compact dimensions, the 628-2Z is widely used in small and medium-sized high-speed rotating components, including:
Motors: Small high-speed motors, stepper motors, small servo motors, fan motors, and vacuum cleaner motors.
Household Appliances: High-speed blenders, hair dryers, robotic vacuum cleaners, and power tools such as rotary grinders and compact grinding machines.
Office Equipment: Printers, scanners, binding machines, and copier rollers.
Sports Equipment: Roller skates, skateboards, and small rollers.
Industrial Equipment: Small conveyor rollers, laboratory equipment, compact instruments and meters, and small textile machinery components.
Precision Compact Mechanisms: 3D printers, DIY machinery, and various compact precision rotating mechanisms.
Recommended Mounting Fits
Shaft Tolerance: j6 / k6 is generally recommended. h6 may be used for light-load, low-speed applications.
Housing Bore Tolerance: J7 / H7
Maximum Shaft Shoulder Diameter (da) ≤ 14.4 mm
Maximum Housing Shoulder Diameter (Da) ≤ 21.6 mm
These shoulder dimensions should be maintained to prevent interference with the bearing's metal shields.
Basic Specifications & Dimensions
| Item | Parameter |
| Bearing Type | Single row deep groove ball bearing, dual shield 2Z (ZZ) |
| Bore Diameter d | 8 mm |
| Outer Diameter D | 24 mm |
| Width B | 8 mm |
| Chamfer r min | 0.3 mm |
| Weight | Approx. 0.017-0.018 kg |
| Cage | Stamped steel plate cage |
| Standard Clearance | CN Normal clearance, optional C3 Large clearance |
| Material | GCr15 Bearing steel (AISI 52100); Stainless steel version model W628-2Z |
Core Performance Parameters
| Performance Item | Value |
| Basic Dynamic Load Rating Cr | 3.9 kN |
| Basic Static Load Rating C0r | 1.66 kN |
| Fatigue Load Limit Pu | 0.071 kN |
| Limiting Speed (Grease Lubrication) | 32000 r/min (2Z Dust Shield) |
| Reference Speed | 63000 r/min (Theoretical Open Type) |
| Operating Temperature Range | -40℃ ~ +120℃ (Standard Lithium Grease) |
| Tolerance Class / Precision Grade | Standard P0, Optional P6/P5 High Precision |
Note: For domestic general brands, the dynamic load is typically 3.35-4.0 kN, static load is 1.4-2.0 kN, and speed is slightly lower. Please pay attention to brand differences during model selection.
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