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grab bucket[′grab ‚bək·ət]
(clamshell), the grasping device of a lift crane, a loader, or an overhead traveling crane, consisting of an assembly of hinged jaws for grasping of loads. The grab bucket is used for transporting and for short-distance handling of loose and segmented loads, timber, and the like. When used for loose materials, the grab bucket operates by digging under and closing on the load. To facilitate picking up material, the jaws of the grab bucket are equipped with teeth. The most commonly used grab buckets for loose materials have a volume of 0.8–1.2 cu m.
The grab bucket for lumber materials (such as logs. pulpwood, and firewood) is similar in its design to the grab bucket for loose materials except that the jaws are of special construction. Each jaw is built with two claws that are bent underneath and linked together by a beam. The use of the grab bucket permits complete automation in the grabbing and loosening of various loads.