The Outer Ring

Manufactured of through-hardened bearing steel, the outer ring is the larger of the two rings and, as the name implies, is the outermost of the two. A highly finished groove on its inside diameter forms a pathway for the balls.

The external surface of the bearing’s outer ring is made in a variety of configurations that mate with the inside bore of the housing. In most instances, the bore of the housing and the outside diameter of the bearing are spherical in shape. This allows the insert bearing to automatically align itself in the housing when the bearing is subjected to misaligned loads.

The outside diameter of the outer ring and the housing bore are manufactured to tight tolerances. This results in a precise fit between the two surfaces, providing proper insert bearing alignment inside the housing and making the unit more forgiving of misalignment. NTN’s tight corresponding tolerances of the outer ring/housing fit eliminate the need for the anti-rotation devices used by other manufacturers. Without the impediment of the anti-rotation device, the replacement of the insert in the housing is much easier.

Insert ball bearings can also be supplied with a straight (cylindrical) outer diameter, which does not allow for misalignment. This type does not fit typical bearing unit housings, but is more commonly sold to be used within housings that are integral components of the application.

The outside edges of the bearing’s outer ring, inner diameter are grooved to hold the seals.

Bearings designed to allow for relubrication have an oil hole in the outer ring, which aligns with a circumferential grease groove in the housing, providing a channel for grease to flow freely from the grease fitting into the bearing.

Typically, NTN product is manufactured so that the holes in the insert and the circumferential grease groove are located on the side of the bearing where the locking device is located. If the application requires that the oil hole and grease groove be on the side opposite the locking device (as is common with the NTN Ultra-Class bearing units), the prefix A is used in addition to the standard insert part number, for example, A-UC206-104D1. More on the NTN numbering system will follow.

Insert Bearing Outer Ring Configurations Options and Corresponding Designations

• A spherical shaped outer diameter without a relubrication hole is considered to be a standard part and carries no suffix designation (ex. UC206-104)
• A spherical shaped outside diameter with a relubrication hole carries the suffix designation "D1." (ex. UC206-104D1)
• A cylindrically (straight) shaped outside diameter is designated by the letter "S." (ex. UCS206-104)
• A cylindrically shaped outside diameter (S) with a snap ring groove is designated with the letter "N." (ex. UCS206-104N)
• A cylindrically shaped outside diameter (S) with a snap ring groove (N) and snap ring assembled in the snap ring groove carries the designation "R." (ex. UCS206-104NR)
• Another possible configuration would be a cylindrically shaped outside diameter (S) with a snap ring groove (N), a snap ring (R) and with relubrication holes (D1). (ex. UCS206-104D1NR)