An Improved Expansion Drill for Well Sinking.

Issue 4 and Volume 7.

An Improved Expansion Drill for Well Sinking. In this drill the blades are made expansible for the purpose of being passed through the casing and then thrown out to cut an opening of sufficient diameter for the easing to pass down. The construction is such that the weight of the drill-rod is utilized in opening the bits or blades, while the raising of the rod closes the blades. The form of the head and manner of mounting the blades between the ears of its lower part are clearly shown in the engravings. The upper edge (within the head) of each blade is so formed as to have a corner which, when the blades are folded or closed, stands above the other corner, so that when struck the cutting portions of the blades will be thrown out. Within and extending across the head is a vertically sliding block arranged to strike…

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