The Cylindrical Needle Bearings
Linear Roller Bearings
Most linear bearings are shaped in the way their name suggests; linearly. However, the needle bearings are circular, shaped like a wide metallic doughnut whose edges are filled with rotating rollers to aid in the movement of whatever they are attached to. They reduce the friction of the rotating components between which they are placed, such as parts of the transmission in an automotive vehicle. This enables all parts involved in the motion process to last longer and run more smoothly, cutting down on maintenance costs for the owner of the vehicle or machine.
Automotive manufacturers are not the only industrial manufacturers to make use of needle bearings. The aerospace industry also utilizes smaller versions of the linear motion bearings for aircraft controls as well as transmissions. Agricultural and construction machines may also use needle bearings for internal functions, as do robotic automation and manufacturing machining industries. Most of these applications require heavy duty and high speeds, which means that the needle bearings must be very well manufactured. That is why stainless steel, as well as other steel alloys, is a popular material choice. With high corrosion resistance and immense strength even when designed in thin layers, these metals respond to motion without friction create very long-lasting pieces.
Although always cylindrical, not all needle bearing designs are the same. Two of the major styles are known as full compliment needle roll bearings and caged needle roll bearings. The full compliment version involves a maximum amount of rollers on the interior of the cylinder, protected by a smooth covering on the outside that keeps the rollers permanently in place. This design keeps vibration to a minimum. The caged needle roller bearings keep their rollers in place by way of guides, which are known as retainers. They limit the amount of rollers that can be fit into the bearing, but are able to move at higher speeds.