Retainer

Retainers keep the balls evenly spaced around the raceway preventing ball to ball contact and thus allowing higher speeds. They also help to retain grease around the balls and raceways. For greater accuracy and to prevent any additional friction, it is important that the retainer is not allowed too much radial movement. To achieve this, the retainer is guided by either the balls or one of the rings. See the sections below for information on how each cage type is guided.

Metal crown/ribbon  
This standard retainer is manufactured from carbon steel for chrome bearings and AISI304 or AISI430 grade stainless steel for stainless bearings. These were often made from brass which also offered a high temperature capability but this is much less common due to higher cost of brass and advances in steel technology.

For higher temperatures, stainless steel is usually recommended. The crown cage and ribbon cage perform the same function but the crown cage is used primarily on smaller miniature bearings and thin-section bearings where space is more limited.Steel cages are preferred for arduous   operating conditions and where high levels of  vibration are experienced.

• Good for low to medium speeds
• Can withstand higher temperatures according to the type of steel (see "Bearing Material" section)
• Crown type - inner ring guided
• Ribbon type - mainly ball guided

Nylon crown (TW)
This moulded synthetic retainer has better sliding characterisitics than the steel cage and produces fewer fluctuations in running torque. It can increase maximum speeds by up to 60 percent so is generally used in high speed applications and has good low noise properties. This retainer is not suitable for low temperature applications as it loses elasticity below about 35°C. In vacuum applications, it may become brittle.
• High speed and low noise
• Max temperature range approx -35 to +110°C
• Ball guided

Phenolic crown (TP)
This retainer is also used for high speed applications. Generally more expensive, it does have advantages over the synthetic type such as absorbency allowing it to be vacuum impregnated with oil for long life application.
• Good oil retention.
• Can operate well with marginal lubrication
• Max temperature approx 140°C
• Inner ring guided

Full complement (F/B)

A full complement (or full ball) bearing contains extra balls and has no retainer. It is used for its greater radial load capacity although axial load capacity is very small. These bearings can only be used at low speeds and bearing torque is increased due to ball to ball friction. An exception is a hybrid full complement bearing (ceramic balls) which can be used for very high speeds. Improved steel and hardening techniques have increased the load capacities of bearings with cages and the full complement bearing is much less common now.
• Higher radial load capacity
• Low speed only (except with ceramic balls)
• Low axial load
• Increased bearing torque