Bearing Parts Descriptions and Terminology

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Ball Bearings Components

The figures below illustrate an assembled Ball Bearing and the terms used to describe each component: Bearing Parts 1 Standard Shield type Component Parts Shield type Flange type Component Parts Flange type External Retaining Ring type External Retaining Ring type  

About Ball Bearing Parts

When discussing ball bearing components, it's important to understand that the main parts of the ball bearing are the races and the balls. There is an outer race, which goes into a bore, and the inner race, in which the shaft rides. The balls are placed in between these two parts to create the rolling properties of the ball bearing. Without these basic parts, there is no ball bearing. That being said, there are other bearing parts to consider, like shields, cages, and flanges. Here you can find a description of some of these types of parts that are available through NMB.


Retainers, also known as cages, keep the balls separated and equally spaced.  Retainer are selected based on the bearing size as well as the required performance.   Ribbon Retainer  

Crown Retainer

Plastic Retainer

Shields and Seals (Enclosures)

Steel Shield Snap Ring

Shield-Snap Ring Type

NMB part number symbol : ZZ

The metal shield is a steel plate secured in the outer ring with a steel snap ring.  
Steel Shield Caulking


NMB part number symbol : KK or HH JIS part number symbol : ZZ The shield is a formed steel plate, secured directly into a recess in the outer ring.    
  Rubber Non-Contact & Contact Seal

Rubber Seal

Symbol SS

Refers to NMB & JIS numbering system. The rubber non-contact seal is constructed with a snap-fit into the outer ring.

Rubber Seal

Symbol DD

Refers to NMB & JIS numbering system. The rubber contact seal provides a positive contact onto the inner ring and is a snap fit into the outer ring.