This machine has a cylinder and valve motion, similar to a steam-engine.
The piston is hollow, the drill-bar which may be of any required length,
passing through it, is moved with the piston, by means of four wedges or
cams on each end of the piston; these cams are pressed on the drill-bar
by means of sliding collars forced upon them by a complex arrangement
operating alternately. The drill-bar is rotated by means of a ratchet
operated by a spiral groove in the shield of the machine. The main
difficulty in this machine was in the complex arrangement for forcing
the collars upon the cams or wedges. It did not work well in a
horizontal position. The machine consisted of one hundred and twenty
pieces, and weighed five hundred and ninety-five pounds.