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6904 Deep Groove Ball Bearing 20x37x9mm
The 6904 bearing marks the point in the 6900 thin-section series where the bore crosses from small-motor territory into light-industrial applications. With a 20mm shaft diameter, 37mm outside diameter, and 9mm width, it delivers 6.38 kN of dynamic load capacity. Three sealing configurations (Open, ZZ, and 2RS) let you match the bearing to the operating environment rather than compromising on speed or contamination protection.
Key Specifications
- Configurations: Open (no seals), ZZ (dual metal shields), 2RS (dual rubber contact seals)
- Load and Speed: 6.38 kN dynamic, 3.65 kN static; 18,000 RPM (Open/ZZ), 14,000 RPM (2RS)
- Radial Direction: Deep groove geometry handles radial loads and bidirectional axial thrust
- Temperature: -40 to 120°C with standard grease; wider ranges on request
- Material: GCr15 bearing steel (AISI 52100 equivalent), ABEC-3 tolerance class
For any inquiries, please contact with our Supporting Team at sales@yuanhecd.com.
| Model | 6904 |
| Type | Open/Shielded/Sealed |
| Bore Dia (d) | 20 mm |
| Outside Dia (D) | 37 mm |
| Width (B) | 9 mm |
| ABEC Tolerance | ABEC-3 |
| Dynamic Load Capacity (kN) | 6.38 kN |
| Static Load Capacity (kN) | 3.65 kN |
| Max. RPM | 18,000 RPM (Open/ZZ) / 14,000 RPM (2RS) |
| Temp. Range (℃) | -40~120℃ |
| Material | GCr15 (AISI 52100) |
| Shield/Seal | SPCC (ZZ) / NBR+SPCC (2RS) |
| Lubrication | Grease |
Bore (d)
20 mm
OD (D)
37 mm
Width (B)
9 mm
Dyn. Load
6.38 kN
Stat. Load
3.65 kN
Max RPM
18,000
Sealing Configurations
The 6904 bearing is available in three seal types. On a single production line, Yuanhe ships all three variants from the same GCr15 rings and balls. The choice of seal is about which tradeoff fits the application.
The 6904 Open bearing carries no seals. It reaches the full 18,000 RPM and can be re-greased in service through the exposed ball path. Use it inside a housing that already provides sealing, such as a gearbox with oil-bath lubrication or a motor end bell with a separate shaft lip seal. The open configuration also allows oil-mist lubrication, which is common in high-speed spindles where grease churning would generate heat.
The 6904 ZZ bearing uses two pressed-steel shields that lock into the outer ring without touching the inner ring. The non-contact labyrinth gap blocks splashes and coarse particles while adding no friction drag, so the bearing retains the 18,000 RPM rating. Factory-filled with polyurea grease, the ZZ variant needs no re-greasing over its service life. Choose ZZ when speed matters and the environment has occasional fluid splash but no fine abrasive dust.
The 6904 2RS bearing uses two nitrile rubber (NBR) contact seals bonded to a steel insert. The seal lip presses against the inner ring groove, creating a positive barrier against fine dust, moisture, and washdown fluids. The tradeoff is speed: contact friction drops the rating to roughly 14,000 RPM. Choose 2RS for outdoor equipment, agricultural machinery, food-processing conveyors, or any application where the bearing sees direct spray or airborne grit.
Performance
At 6.38 kN dynamic and 3.65 kN static, the 6904 bearing carries 39% more load than the 6903 bearing (4.60 kN) while adding 3mm to the bore and 7mm to the OD. That 6.38 kN equates to approximately 650 kg of radial force; enough for a bicycle bottom bracket under hard pedaling, a small centrifugal pump impeller, or a tensioned belt drive on a packaging machine.
The 9mm width is one of the 6904 bearing’s defining features. It is 2mm wider than the 6903 bearing (7mm), and that extra cross-section raises the static load rating from 2.55 kN to 3.65 kN; a 43% gain. Width, not just OD, drives static capacity in deep groove ball bearings. If your application involves sustained radial pressure (a tensioner pulley under constant belt load, for instance), the 6904 bearing’s wider raceways distribute that force across more ball contact area.
The 6905 bearing steps up to a 25mm bore and 7.04 kN dynamic, but its 42mm OD may exceed the housing envelope. When 37mm OD is the hard limit, the 6904 bearing is the most capable option in the 6900 series. Its ABEC-3 tolerance class keeps radial runout under 0.010mm, which is adequate for the majority of general industrial rotating equipment.
OEM and Customization
Yuanhe ships the 6904 bearing with C3 radial clearance and polyurea grease as standard. For production orders, the following customizations are available:
- Clearance: C2 for precision spindles and high-accuracy shaft fits; C4 for press-fit housings with thermal growth above 80°C
- Grease: Low-noise polyurea (3-5 dB reduction for office and medical equipment); high-temperature ester-based (up to 150°C); food-grade aluminum-complex (NSF H1 for incidental food contact)
- Cage: Standard pressed steel; brass machined cage for high-speed or high-vibration duty; glass-reinforced polyamide for reduced weight and lower running torque
- Material: 440C martensitic stainless steel rings and balls for wet, mildly corrosive, or washdown environments; ceramic (Si3N4) balls for electrical insulation and higher speed
Submit your drawing, part number, or operating conditions for a custom quote. MOQ for clearance or grease modifications starts at 500 pcs. Stainless steel and hybrid ceramic variants are quoted per project.
Applications
Bicycle bottom brackets and hub bearings, electric motor end bells (0.5-2 kW frame sizes), centrifugal pump shafts, belt tensioner and idler pulleys, HVAC condenser fan motors, packaging machine rollers and guides, light conveyor head and tail pulleys, power tool armature shafts, fitness equipment rotating assemblies, agricultural sprayer pump drives, food-processing line rollers, office equipment drum and fuser drives.
Frequently Asked Questions
Which seal type should I choose for a 6904 bearing: Open, ZZ, or 2RS? +
It depends on the operating environment. Choose the 6904 Open bearing if the bearing sits inside a sealed housing that already provides contamination protection and you need to re-grease or oil-mist lubricate the bearing in service. Choose the 6904 ZZ bearing if the environment has occasional fluid splash but no fine dust; the metal shields add no friction, so the bearing keeps the full 18,000 RPM rating. Choose the 6904 2RS bearing if the bearing faces direct spray, outdoor weather, fine abrasive dust, or washdown cycles; the rubber contact seals provide the best contamination exclusion but reduce the speed rating to roughly 14,000 RPM.
What shaft and housing tolerances does a 6904 bearing require? +
The 6904 bearing has a 20mm bore and 37mm OD. For a rotating shaft with a stationary outer ring, the standard fit is an h6 shaft (20 +0/-0.013mm) and an H7 housing bore (37 +0.025/0mm). For a stationary shaft with a rotating outer ring, such as a belt tensioner pulley, use a g6 shaft fit and an N7 housing. Press-fit interference on the shaft typically ranges from 0.002mm for light loads to 0.015mm for moderate radial loads. For applications with aluminum housings, consider C3 or C4 clearance to accommodate the higher thermal expansion of aluminum relative to steel.
How does the 6904 bearing compare to the 6903 bearing in load and size? +
The 6904 bearing measures 20x37x9mm with 6.38 kN dynamic load. The 6903 bearing measures 17x30x7mm with 4.60 kN dynamic load. The step from the 6903 bearing to the 6904 bearing adds 3mm to the bore, 7mm to the OD, and 2mm to the width. That geometry change delivers a 39% increase in dynamic load and a 43% increase in static load (2.55 kN to 3.65 kN). The 6904 bearing also fits a 20mm shaft, which is a common motor frame size, while the 6903 bearing fits a 17mm shaft. If your shaft is 20mm and the housing accepts 37mm OD, specify the 6904 bearing.
Can I order 6904 bearings in stainless steel for corrosive environments? +
Yes. Yuanhe manufactures the 6904 bearing in 440C martensitic stainless steel on request. The rings and balls are hardened to 58-62 HRC, which provides corrosion resistance in fresh water, mild chemical exposure, and outdoor condensation while retaining roughly 80-85% of the chrome-steel load rating. For food-processing washdown environments, pair 440C rings with a food-grade grease. If the application requires full seawater resistance or exposure to aggressive chemicals, contact us with the specific media for a material recommendation. Production MOQ for stainless steel 6904 bearings starts at 500 pcs.
