Engineering Reference

Miniature & Instrument Ball Bearings

Cages (Retainers and Separators)

The cage is the ball bearing component that separates and positions the balls at equal intervals around the bearing's raceway. This component is also called the retainer or separator. When selecting the most appropriate cage for your application, some factors to consider are bearing rotational speed (rpm), starting and running torque limitations, operating temperature range, and noise limitations. In some cases, such as in high-load applications, a full complement design may be the best choice. NHBB can also supply specially designed cages to meet your specific requirements. Please contact NHBB for assistance with optimum cage selection.


Tables of Cages and Separators

The tables and descriptions provided below are a starting point for selecting the appropriate retainer design for most applications. The two standard cage designs are the ribbon, two-piece stamped and crimped (AISI 300 series CRES), and the crown, one-piece stamped (AISI 400 series CRES). In addition to these standard cages, NHBB offers many other retainer designs to meet specific requirements, including precision-machined retainers for ultra-high-speed applications. 


Cages 

DescriptionP/N CodeMaterialMax. Speed (Ref.) dN**Max. Operating Temp.*CommentsTypical Appliations
Ribbon
Two-piece stamped, crimped
RAISI 305 Steel150,000900 °FSuperior starting torque, low costGeneral purpose
Crown
One-piece stamped
HAISI 410 Steel150,000900 °FHigher speed capability than ribbon retainer, low cost

General purpose


Crown
One-piece machined
KB

KC
Phenolic-paper base

Phenolic-linen base 
1,200,000250 °FHigh speed capability
Porous material
Vacuum impregnated with oil

Medical
Machine tools
High speed motors


Crown
One-piece machined
M5Polyamide-imide 1,200,000500 °FHigh speed capability
Requires lubrication
Fully autoclavable

Medical/Dental
High temperature


Crown
One-piece machined
Silver coated
SCPatented composite metal-polymer1,200,000500 °F High speed capability
Self-lubricating
Fully autoclavable 

Medical/Dental
High temperature


Full type
One-piece machined 
KN

KM
Phenolic-paper base

Phenolic-linen base
2,000,000250 °F Ultra-high speed capability
Angular contact bearing only
Porous material
Vacuum impregnated with oil 

Machine tool spindles
High speed motors



Full type
One-piece machined
M4Polyamide-imide 2,000,000500 °FUltra-high speed capability
Angular contact bearing only
Requires lubrication
Fully autoclavable

Medical/Dental
High temperature


Full type
One-piece machined
Silver coated
SFPatented composite metal-polymer2,200,000500 °FUltra-high speed capability
Angular contact bearing only
Requires lubrication
Fully autoclavable

Medical/Dental
High temperature


Crown/Full type T1

Meldin®



PGM

Consult Factory

500 °F




500 °F
575 °F

Pourous polyamide-imide material
Vacuum impregnated with oil

Self-lubricating
Low to medium speed




Low speed
Light load



Cage Diagrams

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R


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H

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KB / KC

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M5

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SC

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KN / KM

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M4


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SF

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T1 (Meldin® & PGM)


Additional Ball Separator Designs

DescriptionP/N CodeMaterialMax Speed (Ref.) dN**Max. Operating Temp.*CommentsTypical Applications
ToroidTTPTFE5,000450 °F Low torque
Low speed
Angular contact bearing only

Slow rotation
Oscillating motion
Cryogenic


SlugSLPTFE1,000450 °F 

Low torque
Low speed 

Gimbal assembly
Slow rotation
Low speed


Diagrams of Additional Ball Separators

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TT


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SL

Table Footnotes

+ Typical Part Number Designation.
* Rings and balls are heat stabilized to 300 °F.
**dN is bore (in millimeters) x rpm.
Additional cage designs and materials available. Please consult with factory.



Standard Cages

Ribbon, Two-Piece, Stamped & Crimped 

One of two standard designs for miniature and instrument ball bearings, the two-piece ribbon retainer includes a closed pocket for good durability and loosely clinched tabs, which are favorable for starting torque. This retainer design is economical and readily available but is limited to lower speed applications. Two-piece ribbon retainers are used in radial bearings.
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Ribbon.

Crown, One-Piece, Stamped 

The one-piece stamped crown retainer is manufactured from hardened stainless steel and has coined ball pockets, which provide a hard, smooth, low-friction contact surface to the balls. This design is very lightweight, smooth running, cost effective, and readily available. The one-piece stamped crown retainer is also used in radial bearings, but it has a slightly higher speed capability than the stamped ribbon design. For speeds exceeding the capabilities of this retainer, a machined retainer should be considered.

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Crown.


Machined Cages


Crown, One-Piece 

For high speed applications, a machined crown retainer design is a more appropriate choice than the two standard designs (stamped ribbon and stamped crown). This retainer is suitable for radial bearings. It is manufactured from a variety of materials to meet specific application requirements, including paper and linen-based phenolics and polyamide-imide. Both phenolic materials can be vacuum impregnated with oil, allowing for better lubricity within the ball pockets. The polyamide-imide material is fully autoclavable, making it well suited for many medical and dental applications. Additionally, polyamide-imide contains a small amount of graphite and PTFE, which aids in lubricity properties. Its lubricity may be further enhanced by a patented silver coating.
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Crown.

Full Type, One-Piece

This retainer design is best suited for ultra-high speed applications. Its balanced, symmetrical design makes it stable at very high speeds. This retainer, which can only be utilized with angular contact bearings, is manufactured from a variety of materials to meet specific application requirements, including paper and linen-based phenolics and polyamide-imide. Both phenolic materials may be vacuum impregnated with oil, allowing for better lubricity within the ball pockets. The polyamide-imide material is fully autoclavable, making it well suited for many medical and dental applications. Additionally, polyamide-imide contains a small amount of graphite and PTFE, which aids in lubricity properties. Its lubricity may be further enhanced by a patented silver coating.

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Full.


Alternative Machined Cage Materials

NHBB manufactures machined cages from the following materials (consult with factory for availability):

  • Meldin® 8100/9000
  • Delrin®
  • PGM
  • PEEK
  • Patented Composite Metal-Polymer (Silver-coated polyamide-imide)

Molded Cages

In addition to the machined retainers listed, the NHBB Precision Division offers a limited variety of molded retainers. These may have a lower speed capability as compared to machined retainers mainly due to the fact that machined retainers can be held to tighter tolerances for critical dimensions.


Trademarks

Meldin® is a registered trademark of Saint-Gobain Performance Plastics Corporation.
Delrin® is a registered trademark of DuPont.