When looking for 6004 bearings, you will often see different designations, such as 6004 and 6004-2RS. This may leave you wondering: What is the difference between a 6004 bearing and a 6004-2RS bearing?
To clarify the differences between 6004, 6004-2RS, and other common variants, I will first explain the essential information about 6004 bearings based on nearly 10 years of bearing engineering experience. You will then be able to identify each type and determine which option suits your application.
Once you know which 6004 bearing you need and are ready to purchase in bulk, you can source it from BKZ Industry. BKZ Industry operates two factories producing 6004 bearings and has 15 years of manufacturing and export experience, helping ensure that every shipment meets the agreed quality requirements.
Part 1. What is 6004 Bearing?
A 6004 bearing is a single-row deep groove ball bearing. Its bearing type, dimensional series, and bore diameter can be identified from the designation 6004:
- 6 indicates a single-row deep groove ball bearing. In the standard basic bearing designation system, bearing numbers beginning with 6 generally identify this bearing type.
- 0 identifies the extra-light series. For bearings with the same bore diameter, a higher diameter-series code generally indicates a larger outside diameter and greater load capacity.
- 04 is the bore code, representing a 20 mm bore diameter.
You may wonder how the code 04 represents a 20 mm bore. For standard metric bearings, the bore-code system is:
- 00 = 10 mm
- 01 = 12 mm
- 02 = 15 mm
- 03 = 17 mm
- 04 and above = bore code × 5 mm
Therefore, the bore diameter of a 6004 bearing is:
04 × 5 mm = 20 mm
The bearing consists of an inner ring, an outer ring, balls, and a cage. The deep raceways guide the balls and allow smooth rotation, while the cage separates the balls and maintains their correct spacing.
Features and Advantages of 6004 Bearings
- Low Friction: The balls make point contact with the raceways, resulting in low friction during operation.
- High-Speed Operation: Because of its low-friction ball design, the 6004 bearing can operate at relatively high speeds when properly installed and lubricated.
- Radial and Axial Load Capacity: The deep raceways and ball design allow the bearing to primarily carry radial loads while also supporting moderate axial loads in both directions.
- Compact and Space-Saving: As an extra-light-series bearing, the 6004 has a compact cross-section and requires relatively little installation space.
- Multiple Replacement Options: The 6004 bearing has standardized boundary dimensions, so products from different manufacturers are generally interchangeable. However, the internal clearance, tolerance class, sealing type, cage design, and other specifications should also match the application requirements.
Part 2. What Are the Dimensions of a 6004 Bearing?
Now that you understand what a 6004 bearing is and how to identify its bore diameter, you may still ask: What size is a 6004 bearing?
A standard 6004 bearing measures 20 × 42 × 12 mm. The table below provides its dimensions and other key specifications based on the 6004 bearings manufactured by BKZ Industry.
| Specification | Details |
| Bore Diameter | 20 mm |
| Outside Diameter | 42 mm |
| Width | 12 mm |
| Number of Balls | Typically 9 |
| Radial Internal Clearance | CN or C3 |
| Closure Options | Open, Z, 2Z/ZZ, RS, 2RS |
| Ring Material | SAE 52100 / GCr15 Bearing Steel |
| Ball Material | SAE 52100 / GCr15 Bearing Steel |
| Cage Material | Pressed Steel as standard; other materials are available |
| Approximate Weight | 66–72 g, depending on the closure design |
Part 3. What Are the Common Uses of a 6004 Bearing?
After learning the basic dimensions of a 6004 bearing, you may also want to know its key applications. As 6004 bearings are compact, suitable for high-speed operation, and capable of supporting light loads, they are commonly used in the following applications:
- Industrial Fans: 6004 bearings support fan rotation, helping the fans run smoothly, quickly, and quietly.
- Washing Machines: 6004 bearings are used in washing machine motors.
- Conveyors: These bearings are commonly installed at the shaft ends of small drive rollers, driven rollers, or tension rollers.
- Drilling Machines: 6004 bearings are used to support spindle rotation.
- Automatic Doors: These bearings are used in supporting, transmission, and guiding mechanisms.
Part 4. 6004 vs. 6004-Z vs. 6004-RS vs. 6004-2RS vs. 6004-2Z
At this point, you already have a basic understanding of the 6004 bearing. As today’s topic, “What is the difference between 6004 and 6004 2RS?” indicates, the 6004 bearing is available in different types. So, what are these types, and what do they mean?
6004 bearings can be divided into five common types:
6004: Without any letters after the number, the bearing is an open type without seals or shields on either side.
6004 Z: Z means a metal shield. One Z indicates that the bearing has a metal shield on one side.
6004 RS: RS means a rubber seal. One RS indicates that the bearing has a rubber seal on one side for protection.
6004 2RS: 2RS means that the bearing has rubber seals on both sides. The RS seals contact the inner ring, which generates more friction but provides better protection against contamination.
6004 2Z/ZZ: 2Z or ZZ means that the bearing has metal shields on both sides. The shields do not contact the inner ring, so they do not generate additional friction. However, they do not provide the same level of protection against contamination as 2RS seals.
From these 6004 bearing types and their definitions, you can see that the key difference between the 6004 and the other types is their different protection methods.
Part 5. 6004 Bearing Cross Reference: DU, DDU, LU, LLU, RU, RD and RK Explained
Understanding the different types of 6004 bearings may not be enough when choosing a suitable one, as many of you may have old branded 6004 bearings with special suffixes such as DU, RD, or RK. You may also want to know what these suffixes mean, whether these bearings can be replaced with other 6004 bearings, and which types can replace them. Here, I will explain these suffixes to help you understand their meanings and determine whether the bearings can be cross-referenced.
| Bearing Number | Brand or Designation System | Meaning | Dimensions | Common Equivalent | Important Note |
| 6004DU | NSK | 6004 deep groove ball bearing with one contact rubber seal; the opposite side is open | 20 × 42 × 12 mm | 6004-RS; NTN 6004LU | DU is NSK’s designation for a single-side contact seal |
| 6004DDU | NSK | Contact rubber seals on both sides | 20 × 42 × 12 mm | 6004-2RS; NTN 6004LLU | DDU is NSK’s standard designation for a double-sealed bearing |
| 6004LU | NTN | One contact rubber seal; the opposite side is open | 20 × 42 × 12 mm | 6004-RS; NSK 6004DU | LU is NTN’s designation for a single-side contact seal |
| 6004LLU | NTN | Contact rubber seals on both sides | 20 × 42 × 12 mm | 6004-2RS; NSK 6004DDU | LLU is NTN’s double-side contact-seal designation |
| 6004RU | Koyo/JTEKT | One non-contact rubber seal; the opposite side is open | 20 × 42 × 12 mm | Approximately 6004-RZ | Offers low friction, but the exact seal design differs by manufacturer |
| 6004-2RU | Koyo/JTEKT | Non-contact rubber seals on both sides | 20 × 42 × 12 mm | Approximately 6004-2RZ | Provides better sealing than metal shields while retaining low friction |
| 6004RD | Koyo/JTEKT or application-specific designation | One ultra-light-contact rubber seal; the opposite side is open | 20 × 42 × 12 mm | No exact universal equivalent | Designed to balance low torque, higher-speed capability and contamination protection |
| 6004-2RD | Koyo/JTEKT | Ultra-light-contact rubber seals on both sides | 20 × 42 × 12 mm | Closest to a low-torque 6004-2RS configuration | Not identical to a standard 2RS bearing |
| 6004RK | Koyo/JTEKT or manufacturer-specific designation | One enhanced contact rubber seal; the opposite side is open | 20 × 42 × 12 mm | No exact universal equivalent | Koyo/JTEKT’s RK design provides stronger sealing than its standard RS design |
| 6004-2RK | Koyo/JTEKT; also offered by some other brands such as KML | Enhanced contact seals on both sides | 20 × 42 × 12 mm | Heavy-sealing 6004-2RS-type configuration | Higher sealing performance may also result in greater friction and a lower permissible speed |
Part 6. What is 6004 C3 bearing?
When choosing between 6004 and 6004 2RS bearings, you may also encounter the 6004 C3 bearing. So, what is a 6004 C3 bearing? Here, C3 indicates that the bearing has a greater radial internal clearance than a bearing with normal clearance. Radial internal clearance is the total possible radial movement between the bearing rings and rolling elements before mounting.
Final Verdict: What is Difference Between 6004 and 6004 2RS Bearing?
Now, let’s come back to the question, “What is the difference between 6004 and 6004 2RS bearings?” The simple answer is that 6004 is the open version, while 6004 2RS is a deep groove ball bearing with rubber seals on both sides, providing better protection than the open 6004 version.
As I have explained everything you should know about 6004 bearings, including their features and advantages, types, applications, branded suffixes, and C3 version, you can now select the correct option based on your application.
To buy any type of 6004 bearing in bulk, contact BKZ Industry. With 15 years of experience and two factories, we can produce the 6004 bearings you need.
