Importance

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Abstract

A shaft enlargement arrangement for a boring system is provided, the shaft enlargement arrangement comprising a hollow column proximate a lower end of the boring system. A reamer section comprising a downwardly tapering first cutter head arrangement is rotatably fitted to the hollow column, with first drive means being provided to rotate the first cutter head arrangement relative to the hollow column so as to bore downwardly a hole having a diameter corresponding substantially to the diameter of the first cutter head arrangement. A boring head arrangement is fitted to an operatively lower end, the boring head arrangement terminating in a downwardly tapering second cutter head arrangement to bore a leading or pilot hole, having a diameter that is less than the diameter of the first cutter head arrangement, as the boring system proceeds to bore downwardly. A thrust section is provided to allow the boring head arrangement to advance relative to the reamer section, with a gripper arrangement being used to secure the shaft enlargement arrangement within the bored hole and to control the advancing of the boring head arrangement relative to the reamer section.

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First Claim