English: Woodcut/drawing of a drill invented by Prof. De Volson Wood of the Stevens institute at Hoboken, N. J. It illustrates various attachments which are used for the purpose of rotating percussion drills as well as for feeding them. The piston, piston rod, drill holder, ratchet for rotation, and enlargement for regulating the feed, constitute a single piece of cast steel. The small valve a is operated by the reciprocating movement of the plug b. Steam is admitted behind the plug b so as to keep it constantly pressed against the plug c, which rests upon the conical surface d. During the backward movement of the piston the small valve is forced upward by the conical surface, and during the forward movement it is moved downward by the pressure of the steam behind the plug b. This small valve admits the motor so as to reciprocate the piston e, and this piston operates the main valve f. The length of the stroke is adjusted by simply turning the piece g. By this arrangement the valve is operated without shock, and hence will not break, and when properly set the main valve will not be opened until the blow is struck. The drill is seized and held automatically by the conical wedges i i, and is rotated by the sloping click k, which rotates about its back edge, coming in contact with sloping teeth l on the enlargement of the piston rod. The click m prevents it from feeding forward, and the click n in a similar manner prevents it from feeding back. The thread on the screw o is made very steep, so that when the piston advances so far as to drive m out of bearing, the pressure of the motor on the forward head, p, during the backward stroke of the piston, forces the cylinder forward, which will cause the screw o to turn, thus securing an advance feed. A false head, r, to prevent the piston from striking the rear head, has the motor admitted and retained behind it by a puppet valve.