Medium-sized Deep Groove Ball Bearing

I. Product Overview​

Medium-Duty Deep-Groove Ball Bearings (abbreviated as MDDGBB) are a core category suitable for medium-load applications. They have an outer diameter ranging from 60mm to 190mm and an inner diameter from 20mm to 100mm. Compared with light-duty bearings, their width is increased by 15%-30%, while it is reduced by 20%-25% compared with heavy-duty bearings, featuring a balanced combination of "moderate load-carrying capacity and compact structure". Primarily designed to bear radial loads, they can also withstand bidirectional axial loads equivalent to 20%-30% of the rated radial load, eliminating the need for additional thrust bearings. They are widely used in equipment such as small and medium-sized motors, machine tool spindles, and conveyor machinery.​

Compared with light-duty bearings, MDDGBBs enhance load-carrying capacity by thickening the wall of inner and outer rings and increasing the number of steel balls. Compared with heavy-duty bearings, they retain the advantage of lightweight design, enabling efficient "one-shaft-one-bearing" transmission in fields like general machinery and auto parts, while balancing performance and economy.​

II. Core Structure and Design Features​

1. Precision Structural Composition​

Medium-Duty Deep-Groove Ball Bearings consist of 4 core components, each optimized around "medium-load adaptation and stable transmission":​

Inner Ring and Outer Ring: Adopt a medium-thickness wall design. The wall thickness is 20%-35% thicker than that of light-duty bearings with the same inner diameter. The main material is SUJ2 high-carbon chromium bearing steel, while carburized steel (e.g., 20CrMnTi) is used in high-strength scenarios. After integral quenching and surface grinding, the surface hardness reaches HRC 60-64, and the fatigue strength is increased by 25%. The precision grade is mostly P6/P5, and can reach P4 in high-precision scenarios, ensuring precise fitting with shafts and bearing housings.​

Steel Balls (Rolling Elements): Feature a medium-diameter and high-quantity design. The diameter is 30%-50% larger and the quantity is 20%-40% more than that of light-duty bearings. The main material is GCr15SiMn high-purity bearing steel, and composite balls (alumina ceramic core with steel coating) are used in high-speed scenarios. The roundness error is ≤ 0.5μm, ensuring uniform contact with the raceway.​

Cage: Designed to balance "strength and lightweight". The mainstream type is a stamped cage made of SPCC cold-rolled steel sheet. Solid brass cages are used in scenarios with a rotational speed ≥ 8000r/min, and reinforced nylon cages (PA66 + 30% glass fiber) are used for models with an outer diameter ≥ 150mm. The friction coefficient is as low as 0.002-0.004, and the no-load noise is ≤ 50dB.​

Seals (Optional): Include double-sided dust covers (2Z, stamped from 0.8mm-1.2mm steel sheets, suitable for dry and clean environments), double-sided contact seals (2RS/2RS1, made of NBR/HNBR rubber, with IP65 protection, suitable for humid/high-temperature scenarios), and double-sided non-contact seals (2RZ, combination of steel sheet and rubber, with rotational speed 15%-20% higher than contact-type seals).​

2. Key Design Characteristics​

Medium-Load Advantage: With a raceway curvature coefficient of 0.52-0.53 and increased contact area, the basic dynamic load rating is 40%-60% higher than that of light-duty bearings with the same inner diameter (e.g., Model 6310 reaches 48.8kN), making it suitable for medium radial loads of small and medium-sized motors and machine tool spindles.​

Wide Speed Adaptation Range: The limiting speed is 6000-12000r/min with grease lubrication and 8000-15000r/min with oil lubrication, adapting to the speed requirements of equipment such as conveyor machinery. The temperature rise under rated speed is ≤ 40℃ (ambient temperature 25℃).​

Self-Alignment Capability: Allows 0.1°-0.5° of shafting deviation compensation, alleviating local overload caused by installation errors and reducing the risk of early failure.​

Easy Maintenance: Some models are marked with the suffix "/W33" (equipped with an annular oil groove and 3 oil holes on the outer ring) for easy grease replenishment. Sealed models are pre-filled with long-life grease at the factory, enabling 12000-18000 hours of maintenance-free operation under normal working conditions.​

III. Main Product Models and Classification​

1. Classification by Size and Load Rating​

2. Classification by Seal and Lubrication Method​

Open Medium-Duty Bearings (No Suffix): No seals, requiring regular lubrication, suitable for machine tool spindles and precision gearboxes.​

Medium-Duty Bearings with Dust Covers (Suffix 2Z): Double-sided steel dust covers, suitable for small and medium-sized motors and fans.​

Medium-Duty Bearings with Contact Seals (Suffix 2RS/2RS1): 2RS (NBR rubber, for normal-temperature humid environments); 2RS1 (HNBR rubber, temperature resistance up to 150℃, for auto engine accessories).​

Medium-Duty Bearings with Lubrication Grooves (Suffix /W33): Equipped with oil grooves and oil holes on the outer ring, suitable for conveyor rollers and printing machine spindles.​

IV. Applicable Industries and Typical Applications​

With the advantages of "medium-load adaptation, moderate speed, and easy maintenance", Medium-Duty Deep-Groove Ball Bearings are widely used in various fields:​

General Machinery Industry: 11kW-15kW motors (Model 6310), Ø80mm machine tool spindles (Model 6212), and input shafts of planetary gear reducers.​

Automotive Industry: Small car generators (Model 6206), air conditioning compressors for medium-sized SUVs (Model 6309), water pumps, and gearbox input shafts.​

Conveyor and Packaging Machinery: Ø100mm conveyor rollers (Model 6308), drive shafts of chain conveyors, and traction shafts of packaging machines (Model 6406).​

Construction Machinery Industry: Hydraulic pumps of small excavators (Model 6312), steering shafts of loaders (Model 6315), and auxiliary shafts of roller vibration wheels.​

Home Appliance and Light Industry: Industrial washing machines over 10kg (Model 6314) and paper feed rollers of medium-sized printing machines (Model 6216).​

V. Summary of Product Advantages​

Balanced Load and Space: Meets medium-load requirements while avoiding the space and weight burden of heavy-duty bearings, simplifying equipment structure.​

Wide Scenario Adaptability: Diverse seal and lubrication designs adapt to normal-temperature, high-temperature, and humid environments, reducing equipment design complexity.​

Stable and Reliable Operation: Optimized contact design and high-strength materials ensure a service life of 20000-30000 hours under rated conditions, with a failure rate < 0.5%.​

High Cost-Effectiveness: With over 90% automation in production, the cost is 30%-40% lower than heavy-duty bearings and 25%-35% lower than cylindrical roller bearings with the same load-carrying capacity, suitable for mass applications.​

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