A backhoe thumb is a hydraulically-operated device used in conjunction with a bucket. It enables the backhoe operator to grip chunks of concrete, rocks and other objects while lifting and moving them out of the way. Called a backhoe thumb because of the way the apparatus closes against the bucket, much like a thumb on a hand, the backhoe is able to grip objects and move them around when equipped with the apparatus. During regular digging, the operator is able to hold the backhoe thumb open and positioned against the backhoe arm and out of the way. The thumb apparatus allows a backhoe to perform many jobs, which can reduce expenses for excavating companies by eliminating the need for another piece of equipment and operator to complete a project.
Experienced backhoe operators have long been able to wedge certain objects between the back hoe's arm and its bucket or digging shovel so that it could be moved out of the digging path. The difficulty comes when the object is too large to come straight up and out of a hole. With the addition of a backhoe thumb to the equipment, the operator is able to not only grip a large object to move it, but the thumb allows the operator to grab, pull and wiggle the object to break it loose. This often eliminates wasted time while the backhoe operator waits for assistance to move an obstacle blocking the digging path.
The typical hydraulic backhoe thumb uses a dedicated hydraulic cylinder to power the thumb open and closed. Attached to the bucket or boom with pins, the backhoe thumb has teeth that are designed to mesh with the teeth on the digging bucket to form a tight grip when closed. There are also non-hydraulic backhoe thumb designs that automatically open and close with the movement of the bucket. This non-hydraulic version is best used when moving large rock or debris piles as well as when loading building site trash into a garbage gondola or dump truck.
Some versions of the backhoe thumb are unmovable and are locked into either an open or closed position. When open, the thumb works by remaining in place while the bucket is manipulated to trap objects between the bucket and thumb. To empty the load, the bucket is simply moved away from the thumb and the objects drop into the trailer, dumpster or pile. While not as versatile as the hydraulic backhoe thumb, the fixed position thumb is an economical option for fixed budgets.