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688 Deep Groove Ball Bearing 8×16×4mm | RHD Bearings

Eight millimeter bore that's infinite in capability despite its finite size.

Meet the 688: With 140kg (1.38kN) of engineering excellence and 8mm precision, this bearing delivers the perfect blend of personality and performance for your critical applications. The most widely used bearing in electronics, small motors, and precision instruments.

8mm
Bore Diameter
16mm
Outer Diameter
4mm
Width
1.38 kN
Load Rating
140 Kg
Load Capacity
0.003 Kg
Weight
Technical Specifications Applications 📞 Call +91-9702081858
688 Bearing 8×16×4mm - RHD Bearings

688 BEARING SPECIFICATIONS

Precision-engineered for reliability and performance

🔍 Common Search Terms

688 bearing dimensions 8mm bore ball bearing ultra-compact bearing miniature gearbox bearing high-speed precision bearing lightweight system bearing

📏Dimensions

d - ID (Bore Diameter)
8mm
D - OD (Outer Diameter)
16mm
B - Width
4mm
688 Bearing: 8 × 16 × 4mm

Bearing Cross-Sectional View

688 Deep Groove Ball Bearing Technical Drawing

⚡Load Ratings

Dynamic Load (Cr) 1.38kN
Static Load (Cor) 0.55kN
Load Capacity (kN) 1.38kN
Load Capacity (kg) 140kg

💡What This Means

Dynamic Load (1.38kN): Maximum force while rotating. Exceeding this causes rapid wear and failure within hours.
Static Load (0.55kN): Maximum force when stationary. Use 80% for safety.
Calculate Your Load: Measure shaft forces, belt tensions, or gear loads. Include shock/vibration factors.
Failure Warning: Overloading causes bearing raceways to crack and balls to flatten permanently.

🔄Speed Limits

Grease Lubrication 35000 RPM
Oil Lubrication 41000 RPM
RHD Z2V2 Bearings 1400 RPM
RHD Z3V3 Bearings 2880 RPM
RHD Z4V4 Bearings 6000+ RPM

💡What This Means

Grease Limit (35000 RPM): Heat generation increases exponentially above this. Grease breaks down, causing seizure.
Oil Advantage (41000 RPM): Better heat dissipation allows higher speed. Required for high-speed spindles.
Safe Operating Speed: Use 90% of limit (31500 RPM) for maximum L10 life of 10,000+ hours.
Failure Mode: Exceeding speed causes cage failure, ball skidding, and catastrophic overheating within minutes.

🔧Material & Quality

Steel Grade SAE52100
Ball Grade G10
Carbon Content 0.95-1.05%
Chromium Content 1.40-1.65%
ISO Standard 15:2011 Compliant

💡What This Means

SAE52100 Chrome Steel: Premium bearing steel - harder than tool steel
G10 Balls: Ultra-precision balls with ±0.25µm tolerance
High Carbon: Superior hardness and wear resistance
Chromium: Adds corrosion resistance and toughness
ISO Standard: Fits any 688 application worldwide

📊Vibration Classes

V2 Grade
Low: 72 μm/s
Med: 48 μm/s
High: 40 μm/s
V3 Grade
Low: 44 μm/s
Med: 28 μm/s
High: 24 μm/s
V4 Grade
Low: 38 μm/s
Med: 12 μm/s
High: 12 μm/s

💡What This Means

V2 Grade: Standard grade - good for general applications
V3 Grade: Low vibration - like a smooth car engine
V4 Grade: Ultra-smooth - for precision instruments
Frequency Bands: Measured across different rotation speeds

🔇Noise Levels

Z2 Grade < 35 dB
Z3 Grade < 31 dB
Z4 Grade (Quiet) < 27 dB
Application Precision Equipment

💡What This Means

Z2 Grade: Quiet as a library - good for most applications
Z3 Grade: Very quiet - like a whisper (40 dB = normal whisper)
Z4 Grade: Ultra-quiet - perfect for bedroom fans, medical equipment
Application: Ideal for sensitive environments

⚙️Internal Clearance

C2 (Tight) 0-7 μm
C0 (Normal) 2-13 μm
C3 (Loose) 8-23 μm
C4 (High Temp) 14-29 μm
C5 (Extra High Temp) 20-37 μm

💡What This Means

C2 (Tight): Precision applications - less play, more accurate
C0 (Normal): Standard choice - works for most applications
C3 (Loose): Better for hot environments - allows thermal expansion
C4 (Exta Loose): Hot or tight-fit setups — extra room for thermal expansion.
C5 (Max Loose): Extreme heat/tight fits or near-limit speeds — maximum expansion allowance

SEAL OPTIONS

Choose the right protection for your application

688-ZZ

Most Popular

Double metal shields

Speed Factor: 0.9 (31500 RPM)
Protection: Dust protection
Lubrication: Sealed for life

When to Use 688-ZZ

Best For: Electronics, small motors, skateboards, general machinery
Conditions: Dry environments, moderate dust, precision applications
Achieves: Excellent balance of speed and protection for most applications
Avoid When: Heavy water exposure, chemical environments, food processing

688-2RS

Protected

Double rubber seals

Speed Factor: 0.7 (24500 RPM)
Protection: Moisture and dust
Lubrication: Sealed for life

When to Use 688-2RS

Best For: Outdoor applications, appliances, automotive systems, dirty environments
Conditions: Moisture, dust, contamination, washdown areas, food processing
Achieves: Maximum protection and zero maintenance requirements
Trade-off: Lower speed limit but superior environmental protection

688

High Speed

Open bearing, no seals

Speed Factor: 1.0 (35000 RPM)
Protection: None
Lubrication: External required

688-Z

Balanced

Single metal shield

Speed Factor: 0.95 (33250 RPM)
Protection: Light dust protection
Lubrication: Pre-greased

688-RS

Protected

Single rubber seal

Speed Factor: 0.8 (28000 RPM)
Protection: Moisture and dust
Lubrication: Pre-greased, sealed

APPLICATIONS

Precision performance across industries

Ultra-Compact Mechanisms

  • miniature gearboxes
  • precision actuators
  • micro-drive systems
  • compact transmissions
  • small power tools
  • hobby mechanisms
  • model engineering
  • miniature robotics

Key Requirements: 8mm shaft with 1.38kN dynamic load capacity, 35,000 RPM grease lubrication, ultra-compact 16×4mm profile for space-constrained applications

High-Speed Precision

  • spindle bearings
  • precision motors
  • high-speed drives
  • optical systems
  • measuring instruments
  • calibration devices
  • sensor assemblies
  • test equipment

Key Requirements: 8mm precision shaft with 0.55kN static load rating, ultra-high speed capability, minimal friction for precision applications

Lightweight Systems

  • portable electronics
  • wearable devices
  • aerospace components
  • medical instruments
  • scientific equipment
  • laboratory tools
  • field instruments
  • mobile applications

Key Requirements: 8mm shaft with 141kg load capacity, lightweight 3g design, reliable 35,000 RPM operation for portable systems

Compatible Models & Shaft Requirements

Find bearings with the same bore size and ensure proper shaft preparation

🔄Related Models

608 (8×22×7mm) 628 (8×24×8mm) 688 (8×16×4mm) 698 (8×19×6mm)

🔧Shaft Requirements

Nominal Diameter 8.000mm
Tolerance Grade h6 (7.991-8.000mm)
Surface Finish Ra 0.8μm max
Runout Tolerance 0.013mm max

🎯Application-Specific Options

High Temperature: C3 clearance recommended
High Speed: RHD V3 & V4 bearings recommended
Corrosive Environment: SS (Stainless Steel) bearings recommended

Professional Expertise & Standards

Technical insights from 20+ years of bearing engineering and manufacturing excellence

📋ISO Compliance

ISO 15:2011 compliant dimensions ensure interchangeability with global bearing standards and seamless replacement in existing equipment.

🔬Material Science

Gcr15 chrome steel composition optimized for ultra-compact bearing applications, providing superior hardness, wear resistance, and fatigue life.

⚙️Precision Engineering

C0 clearance standard for most applications, C3 available for high-temperature use. h6 shaft tolerance recommended for optimal performance.

🔧Professional Installation

Professional installation required for maximum 50,000-hour service life. Proper tools and techniques prevent 80% of premature failures.

📊Performance Comparison

Handles 0.63kN more load than 688 bearings while maintaining ultra-compact design. Superior Gcr15 steel vs. standard steel in competing products.

💰Value Engineering

Best value in ultra-compact bearing category for 1.38kN performance. Quality bearings last 3-10x longer than cheap alternatives, reducing total cost of ownership.

FREQUENTLY ASKED QUESTIONS

Expert guidance for 688 bearing applications

Bearing Selection & Replacement ▼

When should I choose 688 bearing over larger alternatives?

Choose 688 when you need ultra-compact 8×16×4mm profile with 140.76kg (1.38kN) dynamic load capacity for ultra-compact mechanisms, high-speed precision, or space-constrained applications.
Why This Matters
Selecting the right bearing size prevents system redesign, reduces costs, and ensures optimal performance in space-limited applications.
How To Handle It
Measure your shaft diameter (must be exactly 8mm), verify load requirements (≤140.76kg (1.38kN) dynamic), and confirm space constraints allow 16×4mm envelope.
688 is ideal for miniature gearboxes, precision actuators, and ultra-compact mechanisms where every millimeter matters.

Can 688 bearing replace other 8mm bore bearings?

Yes, 688 can replace other 8mm bore bearings if they have compatible outer diameter (≤16mm) and width (≤4mm) requirements, and load capacity needs (≤140.76kg (1.38kN) dynamic).
Why This Matters
Proper replacement ensures system compatibility, prevents premature failures, and maintains performance specifications.
How To Handle It
Verify dimensional compatibility (d×D×B), check load ratings, confirm clearance requirements, and ensure speed limitations are met.
Always check both dimensional and performance compatibility before replacement to avoid system issues.

What applications are 688 bearings NOT suitable for?

688 bearings are NOT suitable for applications requiring dynamic loads >140.76kg (1.38kN), speeds >35,000 RPM, operating temperatures >120°C, or environments with heavy contamination.
Why This Matters
Using bearings beyond their specifications leads to premature failure, increased maintenance costs, and potential system damage.
How To Handle It
For higher loads, consider 689 or 690 bearings. For higher speeds, use oil lubrication. For harsh environments, consider sealed or stainless steel alternatives.
Always verify application requirements against bearing specifications to ensure long service life.
Installation & Maintenance ▼

What tools are needed for proper 688 bearing installation?

For 688 bearing installation, you need precision tools: 8mm bore gauge, micrometer for shaft measurement, bearing heater (80-100°C), clean gloves, and appropriate mounting tools for the 16mm outer diameter.
Why This Matters
Proper tools ensure accurate installation, prevent bearing damage, and maximize service life while maintaining precision requirements.
How To Handle It
Clean all components thoroughly, verify shaft dimensions (7.991-8.000mm), heat bearing to 80-100°C, and use proper mounting techniques to avoid damage.
Never force-fit 688 bearings - the 8mm bore requires precise shaft tolerances for optimal performance.

How often should 688 bearings be lubricated?

Open 688 bearings require lubrication every 3-6 months depending on operating conditions. Shielded/sealed versions are lubricated for life but may need replacement after 2-3 years.
Why This Matters
Proper lubrication prevents wear, reduces friction, and extends bearing life. Over-lubrication can cause overheating, while under-lubrication leads to premature failure.
How To Handle It
Monitor operating temperature and noise levels. For open bearings, use high-quality grease compatible with operating conditions. Replace sealed bearings when performance degrades.
688 bearings in high-speed applications (>25,000 RPM) may require more frequent lubrication due to increased operating temperatures.

What maintenance schedule is recommended for 688 bearings?

For 688 bearings, inspect monthly for noise, vibration, and temperature changes. Clean and relubricate open bearings every 3-6 months. Replace sealed bearings every 2-3 years or when performance degrades.
Why This Matters
Regular maintenance prevents unexpected failures, maintains precision performance, and extends bearing service life in critical applications.
How To Handle It
Establish maintenance logs, monitor operating parameters, and replace bearings proactively rather than reactively. Use vibration analysis for early failure detection.
688 bearings in precision instruments require more frequent inspection due to critical performance requirements.
Troubleshooting & Problem Solving ▼

Why is my 688 bearing making unusual noise?

Unusual noise in 688 bearings typically indicates contamination, improper lubrication, misalignment, or wear. The 8mm bore is sensitive to shaft imperfections and contamination due to its small size.
Why This Matters
Early noise detection prevents bearing failure, maintains system precision, and reduces maintenance costs in ultra-compact applications.
How To Handle It
Inspect for contamination, check lubrication levels, verify shaft alignment and surface finish, and replace bearing if noise persists or worsens.
688 bearings amplify noise due to their small size - what sounds minor in larger bearings can indicate serious issues in ultra-compact bearings.

What causes 688 bearing overheating?

688 bearing overheating is caused by over-lubrication, excessive load (>140.76kg (1.38kN)), high speeds (>35,000 RPM), misalignment, or contamination. The small size makes 688 bearings sensitive to these conditions.
Why This Matters
Overheating accelerates wear, reduces precision, and can cause catastrophic failure in ultra-compact bearing applications.
How To Handle It
Check lubrication quantity and type, verify load and speed limits, inspect alignment, clean contamination, and ensure proper ventilation around the bearing.
688 bearings have limited heat dissipation due to small size - monitor temperature closely in high-speed applications.

How do I diagnose 688 bearing vibration issues?

Diagnose 688 bearing vibration by checking shaft runout (≤0.013mm), verifying balance, inspecting for contamination, and measuring vibration levels against V2/V3/V4 standards for 8mm bore bearings.
Why This Matters
Excessive vibration reduces precision, increases wear, and can damage connected equipment in ultra-compact applications.
How To Handle It
Use vibration analysis tools, check shaft specifications, verify bearing installation, and replace bearing if vibration exceeds acceptable limits.
688 bearings require higher precision in shaft preparation due to their small size and sensitivity to imperfections.
Cost & Performance Optimization ▼

How can I optimize 688 bearing performance for cost efficiency?

Optimize 688 bearing performance by selecting appropriate clearance (C0 for most applications), using proper lubrication, maintaining clean environment, and implementing preventive maintenance to extend service life beyond 50,000 hours.
Why This Matters
Performance optimization reduces total cost of ownership, minimizes downtime, and ensures consistent precision in ultra-compact applications.
How To Handle It
Choose clearance based on application requirements, establish maintenance schedules, monitor operating conditions, and replace bearings proactively rather than reactively.
688 bearings offer excellent value when properly maintained - their ultra-compact size means replacement costs are minimal compared to system downtime.

What factors affect 688 bearing service life?

688 bearing service life is affected by load conditions (≤140.76kg (1.38kN)), operating speed (≤35,000 RPM), environmental cleanliness, lubrication quality, installation precision, and maintenance practices.
Why This Matters
Understanding service life factors helps optimize maintenance schedules, reduce costs, and ensure reliable operation in critical ultra-compact applications.
How To Handle It
Monitor operating parameters, maintain clean environment, use quality lubricants, implement preventive maintenance, and replace bearings based on performance degradation.
688 bearings can achieve 50,000+ hours service life when operated within specifications and properly maintained.

How do 688 bearings compare to alternatives in terms of total cost?

688 bearings offer excellent total cost value for ultra-compact applications due to their ultra-compact size, reliable performance, and low replacement costs. Quality 688 bearings last 3-10x longer than cheap alternatives, reducing total cost of ownership.
Why This Matters
Total cost analysis helps make informed purchasing decisions, considering initial cost, maintenance, replacement, and downtime costs over the bearing's service life.
How To Handle It
Compare initial costs, expected service life, maintenance requirements, and replacement costs. Consider system downtime costs when evaluating alternatives.
688 bearings provide optimal cost-performance ratio for ultra-compact applications when quality and proper maintenance are prioritized.
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