Tapered roller bearings have tapered inner and outer ring raceways between which tapered rollers are arranged. The projection lines of all the tapered surfaces meet at a common point on the bearing axis. Their design makes tapered roller bearings particularly suitable for the accommodation of combined (radial and axial) loads. The axial load carrying capacity of the bearings is largely determined by the contact angle α; the larger α, the higher the axial load carrying capacity (fig 9). An indication of the angle size is given by the calculation factor e; the larger the value of e, the larger the contact angle and the greater the suitability of the bearing for carrying axial loads.
Tapered roller bearings are generally separable, i.e. the cone, consisting of the inner ring with roller and cage assembly, can be mounted separately from the cup (outer ring).
Z&K tapered roller bearings have the logarithmic contact profile that provides optimum stress distribution over the roller/raceway contacts. The special design of the sliding surfaces of the guide flange and large roller ends considerably promote lubricant film formation in the roller end/flange contacts. The resulting benefits include increased operational reliability and reduced sensitivity to misalignment.
Double row tapered roller bearings can carry heavy loads and are stiff. They are suitable for the accommodation of combined (radial and axial) loads and can locate a shaft axially in both directions with a given axial clearance or a given preload. Their main use is in gearboxes, hoisting equipment, rolling mills and machines used in the mining industry, e.g. tunnelling machines. Four-row tapered roller bearings are used successfully worldwide for rolling mill bearing arrangements where rolling speeds are slow to moderate. Because of their design they are able to take up those axial loads which occur in such applications in addition to radial loads and generally no separate thrust bearings are required in such arrangements. This means that the roll necks can be relatively short and the chocks at both sides of the roll can have the same design.
Four-row tapered roller bearings, because of their design, must be installed as complete bearings in the chocks. To enable quick roll changes to be made they must therefore have a loose fit on the roll necks. Loose fits have the disadvantage that the inner rings wander on their seatings under the prevailing load conditions causing wear to the seatings which normally have a lower hardness than the rings. To alleviate the effects of a loose fit to some extent, i.e. to reduce wear, SKF bearings have a helical groove in the bore and/or lubrication grooves in the side faces of the inner rings. These grooves enable lubricant to be supplied to the contact surfaces of the inner ring and seating. Additionally, the grease-filled grooves can absorb the wear particles.
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