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NTN
BEARING CORPORATION OF AMERICA |
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Introduction
to Ball Bearings
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Inner Ring Modifications Most applications require the inside surface of the bearing’s inner ring (bore) to be straight. This is considered "normal" and needs no designation as a specifier. Some applications call for the bearing to be held in place by a lock nut and washer to make field service and replacement much easier. In these cases, the shaft is normally made with a slight taper of 1/12" (for every 12" of distance, the shaft’s diameter would be reduced by 1 inch). Therefore, the bore of the bearing must also be tapered to match the taper of the shaft. NTN’s suffix designation for this is K. Cage (Retainer) Composition The cage is an essential bearing component. It may be constructed using a variety of different materials (steel, brass, nylon) and manufacturing techniques (pressed, machined, molded). Pressed Steel Cages Pressed steel cages are the most common type of cage produced by NTN. In this process, steel is formed (pressed) into the proper shape and size to fit the rolling elements, their spacing, etc. Some steel cages are pressed as a one-piece retainer while others are pressed as two separate halves and assembled to form a two-piece retainer. The assembly methods used for two-piece steel retainers are spot welds, rivets, or bent finger joints. (The bent finger joints are designed into the stamped cage halves and are created when they are folded, or bent, over each other to hold the cage together). Although NTN’s suffix for a pressed steel cage is J, it is seldom used because it is considered to be "standard" unless otherwise specified.
Nylon Cages Nylon cages are designed as a one-piece cage and created by an injection molding process. NTN typically uses glass-reinforced Nylon 66 for these cages; they are identified with the suffix designation T2.
Machined Cages Machined cages may be specified for larger, heavier, more precise bearing applications and are made of either brass, steel or phenolic (a polymer capable of withstanding high temperatures). Since they are machined, they have much tighter dimensional specifications and controls. The NTN suffix designations are listed below.
NTN Designations for Machined Cages
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