Needle Bearings and Lubricants

Needle Bearings

Drawn-cup, full-complement needle bearings consist of a deep-drawn cup (the outer race) with a full complement of needles. In some needle bearings the needles are retained by the cup lips, in others they are retained by the grease. Spherical-ended, rather than trunnion-ended, rollers are used in the grease-retained needle bearings, which give a slight gain in load capacity.

Drawn-cup, caged needle bearings are dimensionally identical to full-complement bearings, except that a retainer is used. As usual, the retainer and reduced complement provide higher speeds and reduced load capacity. In addition, the caged bearing has somewhat better tolerance for misalignment than the full-complement needle bearing.

Heavy-duty needle bearings are made with relatively heavy outer rings, made from hardened and precision-ground materials. The needle bearing load capacity is high because of the retainer-guided end-relieved rollers.

Cam followers or track followers are heavy-duty needle bearings with either an integral stud or a nonseparable inner ring that accepts a yoke-mounting stud. The basic follower can include almost any combination of special features such as seals, self-lubricating rings, eccentric-mounted studs, crowned outer races, heavy-duty studs, and a variety of platings and coatings.

Aircraft needle bearings are heavy-duty compact assemblies that have maximum load capacity under static, oscillating, or slowly rotating conditions. The single-roller needle bearings have low tolerance to misalignment. Some double-roller types have a two-piece outer race that compensates for misalignment. All types are provided with grooves and oil holes for relubrication through the shaft or housing.

Thrust needle bearings are caged bearings with rollers assembled like the spokes of a wheel in a waferlike retainer. These needle bearings can operate at fairly high speeds, despite some continuous slippage between the roller and raceway surfaces, which occurs because the rollers are cylindrical rather than tapered.

Needle Bearings