The 6303 bearing is one of the most popular medium-size deep-groove ball bearings in the 6300 series. Its combination of compact size, balanced load capacity, long service life, and wide availability makes it ideal for electric motors, pumps, gearboxes, machinery, and general industrial use.
For engineers, distributors, and equipment repair professionals, understanding the specifications and variations of the 6303 helps ensure proper selection and reliable performance. This guide by BYWB Bearing provides a complete technical overview.
6303 Bearing Specifications
A standard 6303 deep-groove ball bearing features:
Bearing Type: Deep groove ball bearing
Bore (d): 17 mm
Outer Diameter (D): 47 mm
Width (B): 14 mm
Material: Chrome steel (GCr15/52100), stainless steel optional
Cage Material: Steel or nylon depending on manufacturer
Clearance Options: Normal (CN), C3, C4
Load Direction: Mainly radial, with capability to handle moderate axial loads
These are ISO-standardized dimensions, meaning all quality manufacturers produce 6303 bearings in this size.
What Size Is a 6303 Bearing?
The 6303 bearing size is fixed across major brands:
Inner diameter: 17 mm
Outer diameter: 47 mm
Width: 14 mm
This makes size identification straightforward—if the bearing is marked 6303, you can be confident it follows this metric size.
6303 Bearing Interchange Numbers
Since 6303 is a standard part number, many global manufacturers produce fully interchangeable versions. Common equivalents include:
SKF: 6303
NSK: 6303
NTN: 6303
FAG/INA: 6303
TIMKEN/FAFNIR: 303K
KOYO: 6303
NACHI: 6303
Sealed and shielded versions also have interchange formats:
6303ZZ = 6303-2Z (metal shields both sides)
6303-2RS = 6303LLU / 6303DDU / 6303NSE (rubber seals both sides depending on brand)
When replacing a bearing, match:
- The dimensions (17×47×14 mm)
- The closure type (open, ZZ, or RS)
- The internal clearance (standard or C3)
Difference Between 6303, 6303ZZ, and 6303-2RS
6303 (Open Type)
No shields or seals
Allows re-lubrication
Lowest friction / highest RPM
Best for clean environments or when external lubrication is available
6303ZZ (Shielded)
Metal shields on both sides
Non-contact
Protects against larger particles and retains grease
Very low drag, suitable for high-speed motors
6303-2RS (Rubber Sealed)
Rubber seals on both sides
Best dust and moisture protection
Pre-greased and typically “sealed for life”
Slightly lower RPM limit due to seal contact
Ideal for outdoor, wet, or dusty machinery
Summary:
Choose open if you need serviceability.
Choose ZZ for high-speed, cleaner environments.
Choose 2RS for dirty or wet conditions requiring long-term protection.
6303 Bearing Material Options (How to Choose the Right Material)
Choosing the correct bearing material is essential for ensuring long service life and reliable performance. BYWB offers several material options for the 6303 bearing:
1. Chrome Steel (GCr15 / 52100) – Most Common
Highest hardness and load capacity
Excellent fatigue resistance
Best for electric motors, gearboxes, general machinery
Most cost-effective choice
→ Recommended for 90% of standard industrial applications
2. Stainless Steel (AISI 440C)
Corrosion-resistant
Ideal for humid, chemical, or outdoor environments
Slightly lower load capacity compared to chrome steel
→ Recommended for marine equipment, food machinery, chemical pumps
3. Hybrid Ceramic (Steel Rings + Ceramic Balls)
Silicon nitride (Si3N4) balls
Lower friction, higher speed capability
Excellent for high-speed motors and e-mobility
Longer service life, but higher cost
→ Recommended for high-speed spindles, electric vehicle motors, precision equipment
4. Full Ceramic (ZrO2 or Si3N4) – Special Applications
Non-magnetic, corrosion-proof, low weight
Extreme temperature resistance
Rarely needed for general machinery
→ Recommended for laboratory, semiconductor, and high-temperature environments
How to Choose the Right 6303 Bearing Material
For general machinery → Chrome steel
For humidity / water / chemicals → Stainless steel
For high-speed / low noise motors → Hybrid ceramic
For extreme or special environments → Full ceramic
6303 Bearing Sealing Solutions
Manufacturers offer various seal options:
6303 Open
No closure
Re-grease manually
Best for high-speed machines with clean conditions
6303Z / ZZ Shields
Made of sheet steel
Help retain grease
Non-contact, so they allow higher speeds
Provide minimal contamination protection
6303RS / 2RS Seals
Rubber seals
Contact-type, providing tight sealing
Protects against water, dust, and chemicals
Ideal for pumps, outdoor equipment, power tools
Brand-Specific Seal Types
LLU (NTN): Contact seal
LLB (NTN): Non-contact seal
DDU (NSK): Contact seal
NSE/2NSE (NACHI): Contact seal
Knowing your required seal structure ensures the bearing matches both speed and environmental requirements.
What Is a 6303 Bearing Used For?
The 6303 bearing is widely used in:
Industrial Equipment
Gear motors
Reduction gearboxes
Industrial machinery
Blowers and fans
Automotive Equipment
Alternators
Pumps
Small engine components
Electric Motors
AC and DC motors
Starter motors
Power tools
Home Appliances
Washing machines
Air conditioning motors
Vacuum cleaners
Agricultural & Outdoor Machinery
Lawn mowers
Tillers
Water pumps
With its balance of load capability and compact form, the 6303 is a universal choice across industries.
6300 Series Bearing Size Chart
| Bearing Model | Bore (d) | Outer Diameter (D) | Width (B) |
| 6300 | 10 mm | 35 mm | 11 mm |
| 6301 | 12 mm | 37 mm | 12 mm |
| 6302 | 15 mm | 42 mm | 13 mm |
| 6303 | 17 mm | 47 mm | 14 mm |
| 6304 | 20 mm | 52 mm | 15 mm |
| 6305 | 25 mm | 62 mm | 17 mm |
| 6306 | 30 mm | 72 mm | 19 mm |
| 6307 | 35 mm | 80 mm | 21 mm |
| 6308 | 40 mm | 90 mm | 23 mm |
| 6309 | 45mm | 100mm | 25mm |
| 6310 | 50mm | 110mm | 27mm |
This chart helps you step up or down in the 6300 series when designing or matching bearing sizes.
How to Choose the Right 6303 Bearing (Checklist)
Before ordering, confirm:
✔ Size: 17×47×14 mm
✔ Seal type: Open / ZZ / 2RS
✔ Internal clearance: CN or C3
✔ Material: Chrome steel or stainless
✔ Brand compatibility / interchange
If the bearing will face dust, water, or outdoor use → choose 2RS
If the bearing needs high-speed rotation → choose ZZ
If lubrication is external & regular → choose open type
Conclusion
The 6303 bearing is a highly versatile deep-groove ball bearing widely used in electric motors, automotive systems, machinery, and pumps. Its standardized size (17×47×14 mm) and availability in open, shielded (ZZ), and sealed (2RS) types make it easy to select the right model for any application.
BYWB Bearing provides high-quality 6303 bearings with customizable seals, materials, and clearances to fit your exact engineering needs. If you need a quotation, technical support, or interchange assistance, our team is ready to help.