When Should You Choose Double Row Deep Groove Ball Bearings?

A design engineer is working on a gearbox for a conveyor system. The radial load on the shaft is 8 kN, and the available space for the bearing is limited to a 40 mm bore and a 30 mm width. A single row Deep Groove Ball Bearings with a 40 mm bore has a basic dynamic load rating of 12.8 kN, which is adequate for the load. But the engineer is concerned about the rigidity of the shaft. The single row bearing allows a certain amount of radial deflection under load, which could cause misalignment in the gears. The engineer considers a double row deep groove ball bearing. It has the same bore and width, but a higher load rating and a stiffer characteristic. This guide explains when the double row option is the right choice.

1. What Is the Load Capacity Advantage of Double Row Deep Groove Ball Bearings?

A double row deep groove ball bearing has two rows of balls that share the load. The load capacity is not exactly double that of a single row bearing because the rows are not perfectly aligned and the load distribution is not uniform. In practice, the dynamic load rating of a double row bearing is 1.5 to 1.8 times that of a single row bearing with the same bore and width. The static load rating is 1.6 to 2.0 times higher. The table below compares the load ratings for a 40 mm bore bearing.

The double row bearing achieves a higher load rating within a similar envelope. The outer diameter is the same as the single row bearing, but the width is 5 mm greater. If the available space allows for the additional width, the double row bearing is a more efficient use of radial space. In our factory, we manufacture double row Deep Groove Ball Bearings in bore sizes from 20 mm to 120 mm. Cixi Hengji Bearing Co., Ltd. has been producing these bearings for over 12 years.

2. How Does the Double Row Design Affect Shaft Rigidity and Misalignment?

The double row design increases the rigidity of the bearing assembly. Because there are two rows of balls, the bearing resists radial deflection more effectively than a single row bearing. This is important in applications where the shaft must maintain precise alignment with other components, such as gears or seals. The double row bearing also has a greater resistance to moment loads, which are created when the shaft is subjected to a bending force. A single row bearing can accommodate a small moment load, but the double row bearing can handle a larger moment without excessive deflection. The table below compares the rigidity characteristics of single and double row bearings.

The double row bearing has a lower allowable misalignment than a single row bearing. This means that the shaft and housing must be aligned more precisely. In our factory, we recommend that the alignment tolerance for a double row bearing be limited to 1 arc minute. This is achievable with precision machining of the housing and shaft. If the application cannot guarantee this alignment, a self-aligning bearing may be a better choice.

3. When Is a Double Row Bearing Preferred Over Two Single Row Bearings?

In some applications, two single row bearings are mounted side by side to achieve the same load capacity as one double row bearing. This approach is common in older designs. However, the double row bearing has three advantages. First, it occupies less axial space. Two single row bearings require a spacer or a shoulder between them, which adds to the total width. The double row bearing is a single unit with a compact width. Second, the double row bearing is easier to install because there is only one bearing to mount and align. Third, the double row bearing has a lower friction torque because the internal clearance is optimized for the two rows. The table below compares the two approaches.

For new designs, the double row bearing is usually the better choice when the load capacity of a single row bearing is insufficient and the axial space is limited. For existing designs that already use two single row bearings, the change to a double row bearing may require a redesign of the housing and shaft. In our factory, we can provide application support to determine whether a double row bearing is a drop-in replacement or requires modification. Cixi Hengji Bearing Co., Ltd. offers both standard and custom designs.

4. What Are the Installation and Maintenance Considerations?

The installation of a double row Deep Groove Ball Bearings is similar to a single row bearing, but there are two differences. First, the double row bearing is more sensitive to misalignment. The housing and shaft must be aligned within 1 arc minute. Second, the double row bearing has a higher axial stiffness, so the axial clearance must be set carefully. If the bearing is preloaded too much, the friction torque will increase and the bearing may overheat. If the clearance is too large, the shaft may vibrate. The table below shows the recommended mounting tolerances for a double row bearing.

Summary for Application Engineers

Double row deep groove ball bearings are the right choice when the load capacity of a single row bearing is insufficient, when the axial space is limited, and when higher shaft rigidity is required. They offer a compact alternative to two single row bearings and are easier to install. However, they require more precise alignment and careful setting of the axial clearance. By understanding the load capacity, rigidity, and installation requirements, engineers can select the right bearing for the application. Cixi Hengji Bearing Co., Ltd. has been manufacturing deep groove ball bearings for over 12 years and provides full application support for our customers.

Cixi Hengji Bearing Co., Ltd. manufactures single row and double row Deep Groove Ball Bearings in a range of sizes and tolerances. We provide dimensional drawings, load ratings, and mounting guides for all of our products.