Cages - Bearings - Technical

Bearing Cages / Retainers

The purpose of the cage is to hold and separate the rolling elements (balls) of the bearing.

The most common types of cage used for miniature ball bearings are the two piece ribbon and the one piece steel crown types. The crown type is better suited to low torque , low speed applications. These two types of cage are interchangeable in the majority of applications. These cages are usually made from steel, with the steel grade depending upon the manufacturer. Cages may be made from brass, SAE52100 chrome steel or stainless steel; AISI302, AISI410, AISI430 or AISI440C

Larger bearings (over 10mm bore size) usually utilise a two piece steel riveted cage allowing for higher loads, and more vibrational and acceleration stresses.

Bearings with no cage and extra balls are called full complement type (full complement of balls). Generally these bearings allow for higher loads but slower speeds than caged types. These bearings have a filling slot on the edge of either the inner or outer ring. This is where the extra balls are inserted during assembly.

2 Piece Cages

Diagram of Steel Ribbon Steel Ribbon Brass Ribbon Steel Riveted Cage

1 Piece Cages

Diagram of Steel Crown Steel Crown Synthetic Crown

No Cage

Full Complement Full Complement
Note the filling slot to the lower right of the bearing.

High speed applications require bearings with a crown type retainer manufactured from one of various types of synthetic materials including

  • PEEK®

Please note however that high speed is a relative term. High speed for a 10mm bearing  is not the same as high speed for a 4mm bearing and high speed for a skating application is not the same as high speed for a dental handpiece. 

DELRIN®  and PEEK® are registered trademarks of DuPont.

TORLON® is a registered trademark of BP Amoco Polymers.

Synthetic Cages

Phenolic (KB or KC) Phenolic (KB or KC) Glass Re-inforced
Polyamide (T9H or TNH)
White Nylon (TW) Packed White Nylon (TW)


Cages for other types of bearings

Double Row Self Aligning with Crown Type Cage Acetal Bearing with Acetal Crown Type Cage
Flat Raced Thrust Bearing with Nylon Cage Grooved Race Thrust Bearing with Brass Cage

You can find many types of bearings in the Bearing Shop Online Bearings Online Catalogue pages.

The Small Parts and Bearings has a much larger range of engineering supplies.

Hobby and Engineering Supplies lists a smaller range of products and only the most popular items in each range. They also list many additional hobby specific categories.

For the best range of miniature and small bearings please try the Miniature Bearings Australia website. Miniature Bearings Australia also list a large variety of miniature engineering products.

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