Wednesday, January 29, 2014

Ball Bearings Heat and Clearance

Ball and Roller bearings unmounted have internal clearance. This clearance is an actual air gap. As bearings are mounted and pressed onto shafts some of the air gap is removed. As bearings operate the shaft is normally hotter than the housing causing a thermal unbalance which results in more clearance removal.
There are 3 key points to consider when purchasing a bearing:
1. Clearance of the bearing- When heat is involved, the tolerance of the bearing will determine the amount of space the bearing has to expand. You will typically find bearings with C0 clearance. The next larger clearance is a C3, C4, and then C5. Each clearance allows a certain amount of space between the ball bearing and outer race.
2. The material of the bearing: Under too much heat, chrome steel and stainless steel will rust. This limits the amount of heat the metal can take. Your standard chrome steel can handle up to 250ºF. If a bearing exceeds the heat temperature rating, it will fail. Stainless steel can handle more heat. The metal in high temperature bearings is heat treated to be able to withstand higher temperatures.
3. Cage: You will notice that all of the high temperature bearings have no cage (full compliment). This is due to the fact that the bearings expand under heat. If a bearing is encased in a cage, once heated, the bearing will break the cage causing the bearing to fail.

Wednesday, January 22, 2014

The Needle Roller Bearings Different Types

Machined type: The machined type of needle roller bearing can carry the most weight out of the 3 types. This bearing is manufactured from a
Machined Type Needle Roller Bearings are bearings with a low sectional height and large load ratings. The outer ring has high rigidity and can easily be used even for light alloy housings. These bearings are available in metric series and inch series, both of which have the caged type and the full complement type. It is possible to select a suitable bearing for use under various conditions such as heavy loads and high-speed or low-speed rotations. In addition, there are bearings with and without an inner ring. As the type without inner ring uses a shaft as the raceway surface, a compact design is possible

Drawn type: Drawn cup roller clutches are designed to transmit torque between the shaft and housing in one direction and allow free overrun in the opposite direction. These designs utilize the same small radial section as drawn cup needle roller bearings. The units are compact, lightweight and operate directly on a hardened shaft. These bearings are manufactured from pressed steel molds.  Proper mounting is easily accomplished with a simple press fit in the housing. Clutches and clutch and bearing assemblies are offered both in inch and metric nominal series. The Metric sizes for these bearings start with “HK” and the inch series starts with “SC” on our website.

Cage roller: The caged roller bearings are great for low profile designs in applications. This design is basic and takes up less space than a machined roller bearing. Needle roller and cage assemblies are ready-to-mount, self-contained bearing components. They are an excellent choice for applications that require a very rigid bearing arrangement as well as a high load carrying capacity. If the shaft and housing bore can serve as raceways, needle roller and cage assemblies require minimal radial space. The part number for this bearing starts with a K on our website.