الوصف

Needle bearings are roller bearings with rollers that have high length-to diameter ratios. Needle bearings are used in farm and construction equipment, automotive transmissions, small gasoline engines, gear pumps, small appliance and tool motors, alternators, and aircraft controls.

Needle bearings are usually lubricated with grease, but oil or oil-mist lubrication is preferred for heavy-duty or high-speed applications. Many light-duty needle bearings never require relubrication, but high loads or speeds demand it.

Needle bearings have the highest load capacity for a given radial space of all rolling-element bearings, but their use is limited to bore diameters less than *0 in.

All needle bearings are variations of two basic designs. The first needle bearing design, full complement, has a full complement of needles and contains no retainer. The second needle bearing design, caged needle, contains a retainer or cage for roller guidance and spacing. Caged needle bearings have smaller roller complements and lower load capacities than full-complement bearings. Needle bearings have the advantage of a higher speed capacity; Retainers prevent high-velocity rubbing between adjacent needles and provide more effective roller guidance. Needle bearings also have greater lubricant capacity.