Machine Design

Tapered Bearings

When a tapered bearing is subject to a load, a force develops between the roller and the cone back-face rib because the load tries to squeeze the rollers out of the bearing. Most of the load is carried by normal forces at the cup-roller and cone-roller contacts, but a small force is always present at the roller-cone back-face rib contact. This contact also provides roller guidance, so careful design and precise machining of this surface and roller ends are required. Techniques for lubricating this roller-rib contact area permit high-speed operation of tapered bearings.

Tapered roller bearings are widely used in roll-neck applications in rolling mills, transmissions, gear reducers, geared shafting, steering mechanisms, and machine-tool spindles. Where speeds are low, grease lubrication suffices, but high speeds demand oil lubrication -- and very high speeds demand special lubricating arrangements.

Single-row bearings are the most widely used tapered roller bearings. They have a high radial capacity and a thrust capacity about 60% of radial capacity. The exact percentage depends on size. Variations within the type include tapered bores for frequent removal, pin cages and hollow rollers for higher capacity, and steep roller angles for higher thrust capacity.

Two-row bearings can replace two single-row bearings mounted back-to-back or face-to-face when the required capacity exceeds that of a single-row bearing. If the bearing contact lines converge away from the bearing axis, the bearing is more tolerant to misalignment. If they converge toward the axis, the bearing has higher resistance to moment loading, but lower tolerance for misalignment.

Four-row bearings have characteristics similar to two 2-row bearings mounted side-by-side. They are used to provide high capacity or to accommodate special mounting problems.

TAGS: Bearings
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