6904 Decoder Bearing
The 6904 Decoder Bearing is a thin-section deep groove ball bearing designed for precision rotary encoding and decoding applications. It is commonly used in optical encoders, magnetic decoders, servo feedback units, and other rotary position-sensing devices where low friction, high rotational accuracy, and compact dimensions are essential.
Manufactured by MTWB (Mighty Way Industrial Limited) , a specialized bearing manufacturer with over 18 years of experience serving 100+ global OEM customers, this decoder bearing is produced under strict quality control protocols to meet the demanding requirements of encoder applications.
| Parameter | Value |
|---|---|
| Bearing Type | Deep Groove Ball Bearing (Thin Section) |
| Bore Diameter (d) | 20 mm |
| Outer Diameter (D) | 37 mm |
| Width (B) | 9 mm |
| Chamfer (r min) | 0.3 mm |
| Dynamic Load Rating (Cr) | ~6.4 kN |
| Static Load Rating (C0r) | ~3.7 kN |
| Limiting Speed (Oil) | ~23,000 rpm |
| Limiting Speed (Grease) | ~19,000 rpm |
| Weight (approx.) | 0.036 kg |
Thin-section construction — saves radial and axial space, ideal for compact decoder housings.
Precision raceway geometry — ensures smooth rotation and minimal runout for accurate signal generation.
Low starting torque — reduces mechanical drag on the encoder shaft, improving signal stability at low speeds.
Available variants:
6904 — Open type (no seals)
6904ZZ — Metal shield, dust protection
6904-2RS — Rubber seal, enhanced contamination resistance
Operating Temperature: -30°C to +120°C (standard grease)
Lubrication: Pre-lubricated with high-speed grease; oil lubrication optional for higher speed
Mounting: Suitable for press-fit or light interference fit on shaft and housing
ISO/DIN: 61904
Common cross-reference: 6904, 61904, 6904ZZ, 6904-2RS
Brand equivalents: NSK 6904, NTN 6904, SKF 61904, FAG 61904, KOYO 6904
When selecting a 6904 bearing for decoder use, consider:
Seal type — Open or ZZ for clean environments; 2RS for dusty or humid conditions.
Radial clearance — C0 (standard) or C2 (reduced) for higher precision.
Precision grade — P5 or P6 recommended for low runout in high-resolution decoders.
Lubrication — Low-torque grease for smooth low-speed operation.
The 6904 Decoder Bearing is deployed across a range of precision motion control applications:
●Rotary Encoders and Decoders: Core bearing for incremental and absolute rotary encoders, providing the mechanical support and rotational accuracy needed for reliable position feedback.
●Servo Motors and Stepper Motors: Supports the motor shaft in encoder-equipped servo systems where speed feedback is essential for closed-loop control.
●Industrial Automation: Used in robotic arms, CNC indexing tables, and automated assembly equipment where precise angular positioning is required.
●Medical Devices: Suitable for diagnostic imaging equipment, laboratory automation, and surgical robots requiring smooth, quiet rotation.
●Automotive Sensors: Employed in wheel-speed sensors, steering angle sensors, and electric power steering (EPS) systems.
●Measuring Instruments: Integrated into optical comparators, theodolites, and precision test equipment where angular resolution depends on bearing stability.
●Power Hand Tool Feedback Systems: In advanced cordless tools with electronic speed control, the decoder bearing supports the sensor mechanism that monitors motor RPM for torque management and battery optimization.
MTWB (Mighty Way Industrial Limited) brings distinctive capabilities to 6904 Decoder Bearing supply that
differentiate it from commodity bearing sources:
Customized Decoder Bearing Solutions
MTWB specializes in custom-made bearings to meet unique customer requirements, including special dimensions, non-standard clearances, and application-specific preload settings. For decoder applications, this means the bearing can be tuned to match the exact torque and runout characteristics of a specific encoder design — not merely selected from a catalog.
Precision Micro-Bearing Manufacturing Expertise
Since 2015, MTWB has focused on the production of micro-size, low-noise ball bearings and flanged thin-section bearings. The 6804 Decoder Bearing benefits from this specialization: MTWB's manufacturing processes are optimized for small, precision bearings where tolerances measured in microns directly affect end-product performance.
OEM-Grade Quality at Competitive Cost
MTWB serves 100+ OEM customers worldwide and offers quality bearings at competitive pricing to international OE customers with specified precision levels compatible with international brands. The 6804 Decoder Bearing is available with P5 or P6 precision grades, and full inspection reports (including noise/vibration testing) can be provided upon request.
Flexible Sealing and Lubrication Options
MTWB offers the 6904 Decoder Bearing in multiple configurations: open, ZZ shielded, 2RS sealed, and custom seal designs. Lubrication can be specified as low-noise grease, high-speed grease, or application-specific formulations. This flexibility allows customers to optimize for torque, speed, temperature range, or environmental protection.
Traceability and Quality Documentation
Each production lot includes material certificates, dimensional inspection data, and, where required, rotational torque and noise/vibration test results. MTWB's quality management system supports PPAP documentation for automotive and industrial OEM programs.
Engineering Support for Integration
MTWB provides technical support for bearing selection, interference fit recommendations, and encoder system integration. For customers developing new decoder products, MTWB can assist with prototype bearings, application testing, and design iterations — reducing time-to-market for new encoder platforms.
October 14,2026
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