638
600 Series Miniature Bearings
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Part No.
Part No.
638
Basic Information
Bearing type
Ball
System of measurement
Metric
Construction
Single Row
Weight
28.1 g
Tolerance class
ABEC1
Seal type
Open
For load direction
Radial
Main Dimensions
Bore diameter
8 mm
Bore diameter tolerance
-0.008mm to 0
Outside diameter
28 mm
Outside diameter tolerance
-0.008mm to 0
Width
9 mm
Width tolerance
-0.12mm to 0
Inner Ring Dimensions
Inner ring type
Standard
Ball & Washer Dimensions
Ball diameter
4.762 mm
Ball quantity
7
Performance
Temperature range
-30° to 110 °C
Radial dynamic load rating
873 lbf
Radial static load rating
357 lbf
Limiting speed
28 X 1000 rpm
Lubrication
Required
Radial internal clearance
0.002mm to 0.013mm
Radial internal clearance
MC3
Materials
Ring material
Chrome Steel
Ball material
Chrome Steel
Cage material
Stainless Steel
Environment & Compliance
REACH
Compliant
ROHS
Compliant
Technical Drawings
No drawings available at the moment, will be launched soon
Price:
$ 1.13
/ each
In Stock
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638 Bearing Product Overview & Core Advantages
The 638 metric ball bearing is a single row deep groove ball bearing, representing a fundamental and highly versatile component in mechanical design. Engineered for radial load applications, its open design ensures low friction and high operational efficiency. Manufactured to ABEC1 precision tolerances, this bearing offers reliable performance for a wide range of general industrial uses. Its compact dimensions (8mm bore, 28mm OD) and lightweight construction (28.1g) make it an ideal choice for applications where space and weight are critical considerations.
638 Bearing Model Code Explained, Specifications & Naming Convention
| Code Segment | Technical Meaning |
|---|---|
| 638 | The basic bearing number, indicating a metric, single row deep groove ball bearing with an 8mm bore and 28mm outside diameter. |
| Open (No Seal Suffix) | The bearing is supplied without seals or shields, allowing for high-speed operation and requiring external lubrication and a clean operating environment. |
638 Bearing Structural Features & Performance Benefits
- Optimized Internal Geometry: The deep groove raceway and complement of seven precision chrome steel balls provide excellent capability for handling radial dynamic loads up to 873 lbf.
- High-Speed Capability: The stainless steel cage reliably guides the balls, contributing to stable operation and a high limiting speed of 28,000 rpm.
- Precision & Reliability: Manufactured to ABEC1 tolerance class with a controlled radial internal clearance (MC3 group), ensuring consistent performance and smooth rotation.
- Robust Material Construction: Rings and balls made from chrome steel offer high hardness and durability, while the stainless steel cage provides excellent corrosion resistance.
638 Bearing Typical Application Areas
This 638 bearing is widely used in various compact and high-speed machinery, including:
- Small electric motors and gearboxes
- Precision spindles and rollers
- Power tools and handheld appliances
- Medical and dental equipment
- Office automation equipment (printers, scanners)
- Radio control models and drones
