rock-drill

Century Dictionary and Cyclopedia

1. n. A machine-drill; a drill worked by steam-, water-, or horse-power: distinguished from a drill worked by hand. In the accompanying figures A, A are the legs which support the working parts shown in the section. The legs form a tripod stand which is pivoted at C to the bed-plate D. The legs are weighted at B to hold the machine firmly when at work. The bed-plate has guideways E formed on its upper surface, one of which is shown in the section. To these ways are fitted guides on the cylinder F. A standard G is bolted to the back of the bed-plate, and at its upper end has a fixed bearing I for the feed-screw H. A winch J is used to turn the feed-screw, which, as the latter cannot move vertically, operates in the nut I' to raise or lower the cylinder F together with all its attachments; K is the steam-chest and valve-box with bonnets K'. Steam is supplied to K by a steam-hose L; M (in the section) is the steam-thrown induction-valve, which also controls exhaust after the manner of the common slide-valve, but is cylindrical in form and is moved by the action of the steam admitted to K; N is the piston; N', the piston-rod; N”, the drill, fitted to a socket O in the exterior end of N; P and P are parts of the mechanism which turns the piston, piston-rod, and drill a short distance on their vertical axis at each stroke of the piston.