In this article we will see in details about the roller/radial bearings, and its types and dimensions.
Parts in Bearing
##Seals and Shields To help retain bearing lubrication and prevent contamination from the environment a seal (contact) or shield (non-contact) can be employed.
Often no seal (Open) is required when the bearing will be housed and externally lubricated or when operated in a vacuum.
|Shield||Z||They have fair dust resistance and poor water resistance. Shields are good to around 350 F.||Lowest in price, hence good for prototyping and low end application||The Z type shield is a metal shield that typically is non-removable after installation as is it pressed in. There is a small gap about .005 inches between the shield and inner race. There is no contact so obtainable speeds and torque are not effected as in a contact type seal. Lubricant leakage can occur and contamination can enter through this gap.|
|Seal||RS||Generally the speed rating is reduced about 35% that of the Z type or open and torque is increased. Temperature range is 15 F to 220 F||Costlier than Z type||The RS type seal is a rubber seal that makes contact with the inner race. Most commonly made of Buna-rubber. They are removable. They offer the best sealing against contamination and lubricant leakage.|
|Seal||V||Speed rating is not reduced and is comparable to that of the Z type or open. There is no seal induced torque increase. Temperature range is 15 F to 220 F||Costlier than RS type||Seal is a non-contact type rubber seal that does not contact the inner race, but rides in groove machined in the inner races creating a labyrinth effect. Its performance falls between a metal shield and contact type rubber seal. Most commonly made of Buna-rubber. They are removable. They offer the good sealing against contamination and lubricant leakage.|
|Seal||T||High temperature capability of 500 F||Availability is rare and very costly||The seal is made of glass reinforced Teflon. This type of seal is removable and easily replaced. In most configurations the seal is held in place by a snap ring. The level of contact (sealing) can be adjusted to meet application requirements all the way from non-contact to heavy contact.|
Dimensions of Miniature Bearings
|Bearing No||Bore Dia (d) mm||Outer Dia (D) mm||Width (B) mm|
Based on the number of number of the shields/seals and size the bearings are named,
For example 608 number specifies the dimension (refer Dimensions section) of a bearing, following letters/numbers says its seal/shield type.
|608 Z||Shield on single side only, other side is open|
|608 ZZ||Shields on both side|
|608 RS||Seal on single side only, other side is open|
|608 2RS||Seals on both side|
Still there are more you can read about bearing on wikipedia.org