iCBcult of access. sequently that the drill was brought to a sufficiently The electrical features fiexible cable. practical state to compete with other drills operated One of the most noteworthy features of the drill is of the system are so ex- by compressed air or steam. Within the past few the… … silica. The drills in this mine work to particular ad- revolutions per minute. Every revolution of the arma- Fig. 1.—THE HABVIN ELECTBIC BOCK DBILL. vantage, owing to the very large face walls upon which ture produces one complete stroke of the drill. The they operate, and which permit of…
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