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Koyo Technical Information

1. Types of rolling bearings and characteristics
   • Angular contact ball bearings
   • Outline of bearing selection

a. Angular contact ball bearings

Single-row	Back-to-back arrangement	Face-to-face arrangement	Tandem arrangement	Double-row
	DB	DF	DT	With filling slot
7000, 7200, 7300, 7400 … Contact angle30° 7000B, 7200B, 7300B, 7400B … Contact angle40° 7900C, 7000C, 7200C, 7300C … Contact angle15° HAR900C, HAR000C … Contact angle15°				3200 3300 Contact angle 32°	5200 5300 Contact angle 24°

• Bearing rings and balls possess their own contact angle that is normally 15°, 30° or 40°.
  Larger contact angle — higher resistance against axial load
  Smaller contact angle — more advantageous for high-speed rotation
• Single-row bearings can accommodate radial load and axial load in one direction.
• DB and DF matched pair bearings and double-row bearings can accommodate radial load and axial load in both directions.
• DT matched pair bearings are used for applications where axial load in one direction is too large for one bearing to accept.
• Angular contact ball bearings are used for high accuracy and high-speed operation.

b. Outline of bearing selection

Currently, as bearing design has become diversified, their application range is being increasingly extended. In order to select the most suitable bearings for an application, it is necessary to conduct a comprehensive study on both bearings and the equipment in which the bearings will be installed, including operating conditions, the performance required of the bearings, specifications of the other components to be installed along with the bearings, marketability, and cost performance, etc.

For reference, general selection procedure and operating conditions are described as follows. There is no need to follow a specific order, since the goal is to select the right bearing to achieve optimum performance.

In selecting bearings, since the shaft diameter is usually determined beforehand, the prospective bearing type is chosen based upon installation space, intended arrangement, and according to the bore diameter required.

Next, from the bearing specifications are determined the service life required when compared to that of the equipment in which it is used, along with a calculation of the actual service life from operation loads.

Internal specifications including bearing accuracy, internal clearance, cage and lubricant are also selected, depending on the application.

Fig 1: Bearing selection