| 摘要 |
An extendible tool holder having one end adapted for attachment to the shank of a drill bit and the other end adapted for attachment to a spindle. The tool holder includes an elongate shaft portion having a hexagonal cross-section slideably disposed within a sleeve portion. Each face of the shaft portion has a plurality of ball detent rests in the for of circular indentations therein. The distance of the detent rests from the end of the shaft are different from one another on adjacent faces of the shaft. Staggering the detent rest spacing by deploying the detent rests on adjacent faces of the shaft enables adjustable extension of the tool holder without sacrificing structural integrity. A hollow cylindrical sleeve having ball detents therewithin and a spring-loaded ball detent releasing collet thereupon slides telescopically over the shaft. The sleeve portion has a lumen having a hexagonal cross-section therewithin and coextensive therewith which matingly accommodates the hexagonal shaft portion of the tool holder as well as the shank of a tool. The hexagonal cross-section of the exterior of the shaft portion, together with the hexagonal lumen of the sleeve portion provides structural integrity during high torque operations. In a preferred embodiment, the tool holder is suited for extendibly attaching a drill bit to a drill chuck. One end of the hexagonal shaft portion is held within a drill spindle. The opposite end of the shaft projects into one end of the hexagonal lumen within the sleeve portion. The shank of a drill bit extends into the other end of the lumen and is held securely thereby. The shaft portion and sleeve portion are telescopically adjusted to space the drill bit a preferred distance from the drill spindle.
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