Product Introduction

The 6700 series represents the ultra-thin-walled category of single-row Deep Groove Ball Bearings; among all standard Deep Groove Ball Bearings, this series features the thinnest cross-section, the smallest outer diameter, and the narrowest width. Model numbers begin with "67" (e.g., 6704, 6705, 6706).

The 6700 series is designed for extreme applications: providing rotational support in environments with severely limited radial space, very light loads, and extremely high rotational speeds. It is the "ultra-thin" specialist within the deep groove ball bearing family.

Single row deep groove Ball Bearings are the most representative type of rolling bearing and are widely used. They primarily consist of an inner ring, an outer ring, steel balls (rolling elements), and a cage. In addition to open designs, these bearings are available with steel dust shields (ZZ type), rubber seals (2RS type), or snap rings on the outer ring (NR type). Pressed steel cages are commonly used.

Single Row Deep Groove Ball Bearings exhibit low frictional torque, making them ideal for environments requiring high speeds, low noise, and low vibration. They primarily support radial loads but can also handle moderate bidirectional axial loads. When radial internal clearance is increased, they acquire characteristics similar to angular contact ball bearings, allowing them to withstand alternating axial loads in both directions.

Structure and Characteristics

The 6700 series features extremely compact cross-sectional dimensions—the outer diameter is only slightly larger than the inner diameter, and the width is very narrow (often just 3–4 mm for many models). This ultra-thin-walled design offers the following characteristics:

Thinnest and Narrowest: Features the smallest outer diameter and narrowest width of any series; occupies minimal radial space, making it suitable for equipment with extremely tight spatial constraints.

Lightest Weight: Minimal material usage results in very low weight, significantly helping to reduce the overall weight of the equipment.

Extremely High Speed: Tiny steel balls generate minimal centrifugal force and frictional heat, resulting in the highest limiting speeds among all deep groove ball bearings. Minimal friction: Small contact area and extremely low starting friction torque ensure highly flexible operation.

Lowest load capacity: Due to cross-sectional constraints, the steel balls are tiny and few in number; radial and axial load capacities are very low, making them suitable only for extremely light loads.

Poorest rigidity: The rings are extremely thin and prone to deformation, requiring very high precision and roundness for the mounting housing bore.

Limited selection: Fewer specifications available, primarily in small to medium sizes; limited options for seal types and cage designs.

Dimensional Parameter Table

Common Suffixes

Open: Standard 6700 series products are mostly open-type, as the thin walls limit seal design options.

ZZ: Some models offer double-sided metal shields, though the shield structure is specialized due to the thin walls.

2RS: Some models offer double-sided rubber seals, but options are limited, and the limiting speed is reduced when sealed.

C2 / C0: The 6700 series primarily features standard C0 clearance; C2 (reduced clearance) is used for precision applications, while C3 (increased clearance) is rare.

/P5 / P4: The 6700 series is frequently used in precision equipment, offering a wider range of high-precision grades (P5/P4) compared to standard series.

Cage: Typically stamped steel or copper alloy cages; nylon cages are rare (due to thin walls).

Application Scenarios

The ultra-thin wall characteristics of the 6700 series make it suitable for the following specialized applications:

Precision instruments and meters: Measuring instruments, analytical instruments, optical instruments, and medical equipment—characterized by extremely limited space, very light loads, and requirements for high precision and low noise.

Aerospace equipment: Gyroscopes, attitude control mechanisms, and satellite equipment—highly sensitive to weight and volume; involves light loads and high speeds.

Robotics and automation: Small robot joints, harmonic drives, and servo motor encoders—characterized by compact space, light loads, and high precision requirements.

Semiconductor equipment: Wafer transfer mechanisms, lithography machine components, and inspection equipment—requires clean environments, light loads, and high precision.

Office equipment: Precision rollers and gears in printers, copiers, and scanners—characterized by limited space and light loads. Models and Hobbies: High-end aircraft models, car models, drones, and RC equipment—sensitive to weight and size.

Medical Equipment: Surgical robots, dental handpieces, and small pumps—requiring miniaturization, low noise, and high precision.

Textile Machinery: High-speed spindles and precision yarn-guiding mechanisms—high speed, light load, and space constraints.

Key Differences

The 6700 series represents the "ultra-thin-walled" variant of deep-groove ball bearings; the distinction from other series can be understood as a progression from "thin" to "thick":

6700 Series (Ultra-thin-walled): Thinnest and lightest, smallest outer diameter, highest speed, lowest load capacity—for precision, light-load applications with extreme space constraints.

6800 Series (Thin-walled): Slightly thicker than the 6700 series, with a larger outer diameter and higher load capacity; a common choice within the thin-walled category.

6900 Series (Thin): Thicker than the 6800 series, offering improved load capacity and rigidity; highly versatile among thin-walled series.

6000 Series (Extra-light): Enters the standard series range; outer diameter and width are significantly larger than thin-walled series; moderate load capacity and good versatility.

6200 Series (Light series): The most balanced and versatile option; highest usage volume.

6300/6400 Series (Medium/Heavy series): Robust and sturdy with the highest load capacity; represent the opposite extreme to the 6700 series.

Selection Recommendations

Verify if ultra-thin-walled bearings are truly necessary: The 6700 series has very low load capacity and rigidity, limited options, and high costs; consider it only when radial space is extremely restricted and the 6800, 6900, or 6000 series cannot be used.

Strictly verify load capacity: Due to the very low load capacity of the 6700 series, carefully calculate service life based on actual loads to ensure requirements are met. Even slight overloading can lead to premature failure.

Check housing bore precision: The rings of the 6700 series are extremely thin and prone to deformation; they demand very high precision regarding the housing bore's roundness, cylindricity, and surface roughness. Insufficient precision in the housing bore can lead to bearing deformation, increased noise, and a shortened service life.

Exercise extreme caution during installation: Thin-walled rings deform easily. Use specialized tools to apply even pressure, and strictly avoid hammering or misalignment. Thermal mounting is recommended to prevent ring deformation during press-fitting.

Prioritize high precision: The 6700 series is commonly used in precision equipment; selecting a precision class of P5 or higher is recommended to ensure rotational accuracy and low noise.

Ensure appropriate lubrication: Thin-walled bearings have very limited internal space, so the grease fill quantity must be strictly controlled (usually filling one-third of the space is sufficient); excessive grease causes heat generation due to churning.

Consider alternatives: If space permits, the 6800 or 6900 series offers superior load-bearing capacity, rigidity, and cost-effectiveness compared to the 6700 series, making them more reliable choices.