Machine Design

Unground Ball Bearings

Unground ball bearings may be wholly unground, ground in part, or wholly ground, but are characterized by precision levels less than ABEC 1. They are available in the traditional ball bearing forms to accommodate radial, thrust, and combined radial-thrust loads.

Materials: Low-carbon steels are employed widely; they are carburized and hardened to obtain enough wear resistance for good service under normal conditions. Certain applications require the corrosion resistance of stainless-steel or plated surfaces. In low noise applications, a variety of elastomeric compounds are molded or bonded to the outside diameters.

Tolerances: A proportion of 10:1 is reasonably close when comparing the tolerances on an unground bearing to those of a precision bearing. Thus, where 0.0005 in. might be specified for a ground bore, 0.005 in. is the norm for an unground bore.

Ratings: Failure in unground bearings is usually caused by wear, as compared with metal fatigue in precision bearings. Therefore, unground bearings do not exhibit the uniform statistical life tests results common to precision bearings. In the less-than-ABEC-1 category, ground bearings use the standard rating method used for conventional rolling-element bearings. But unground bearing capacities are generally drawn from experience, thus life values are not stated.

TAGS: Bearings
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