DRIFTWAY. 464 DKILL. ae a public right, in highways, unless restricted by statute or the terms of the dedication of the lii-jliway, or it may exist as an cuscmoit over the lanil of another, aeqnired by prant or |)re- seription. Not every easement of a way is a driftway, however, nor even every general ripht of way — the latter hcin^' eonimonly restricted to the more usiuil inirposes of a way, as passing and repassing on foot or with horses and wagons. A way "for all purposes' lias, however, been held to include a driftway. See Kasemext; High- way; Way. DRILXi (from Dutch. Cer. drillcn, to drill, connected ultimately with .S. Jji/rc/mii, to bore. Kng. Ihrill). In the broadest meaning of the word, a drill is a tool used in boring or making holes in metal, bone, ivory, wood. etc. Drills for boring wood are described under HoRiNC, M.- ClllXEs. Rock drills, or rock drilling machines, are a separate class of tools, and are descrilH'd separately below. Drills for metal, bone, ivory, etc., are made in several forms. One form con- sists of a square steel bar, flattened out at the cutting end. This end is brought to an angular point like a spear-head, and the cutting edges forming the angle are beveled in opposite direc- tions. Those which have a jirojecting pin in the centres and chisel-shaped cutting edges on each side of the pin are called "centre bits.' There are various contrivances by w hich the drills are made to revolve. For drilling iron, steel, and large brasswork. the drilling machine (see Metai.- WoRKIxc. MAnilNERY) is commonly used. The best and most generally used drills for small boring are called twist drills, which have many advantages over the flat drills described above. Twist drills are made from steel rods of uniform diameter throughout their length. Upon the rod two spiral grooves are cut. each starting at the cutting edge at diametrically opposite points. At the end of the drill the grooves almost meet in the centre of the rod. but grow shallower as they continue. Tlie cutting e<lges are ground on the end of the rod and the borings escape through the grooves, which constantly carry them away from the cutting edge, thus preventing clogging. Rock Drills. These may be divided into two general classes — viz. hand drilN and power drills. Briefly described, a hand drill is a bar of steel having a chisel-shaped end or cutting edge. The simplest form of hand drill is worked by one man. who holds the drill in one hand and drives it with a hammer wielded by his other hand. A tnore cfTicicnt method of hand-drill work is, how- ever, where one man holds the drill and another swings the hammer or sledge. Another form of hand drill, called a churn drill, consists of a long heavy bar of steel, which is alternately raised and dropped by the workman, tlius cutting a hide by re|ieatcd impacts. In drilling by hand, the workman holding the drill gives it a partial turn on its axis between strokes, in order to prevent wcdginu and to offer a fresh surface to the cut- ting edge. When the conditions arc such that use can be made of them, it is nearly always preferable to use jmwer drills, on accimnt of their preater speed of penetration and greater economy of work. Power Drills are worked by direct steam pressure, or by compressed air generated by Bteani or water power, and stored in reieivers, fnmi whi'll it i< led to the drills through iron pipes. (See Aiu Compressors.) There are a great variety of s|X'cial forms of [Kiwer drills, but they can nearly all be grou|H'd in one of two classes: (1) ]'rrcus.sion drills, and {'2) ratarii (Irilh. The first .merican piTi'Ussion drill was l)atented by ,1. ,T. Couch, of Philadelphia. Pa., in -March, 1849. In May of the same year. Mr. Joseph W. Fowle. who had assisted Mr. Couch in devehiping his drill, ])atented a percussion drill of his own invention. The Kowle drill was im- proved by Mr. Charles Hurlcigh. and was first used in the Hoosac Tunnel. (See Tinnels.) In Kurope. M. CarO patented a percussion ilrill in Prance, in October. lSr)(!. This invention was soon followed by several others; but it was not until Sonmieiler's drill, ))atented in I8;>7 and jierfected in IStil, was used on the Mont Cenis tunnel, that the problem of the per- cussion drill was practically solved abroad. Since that tinu" numerous percussion- drill patents have been taken out in both America and Eu- rojie. . percussion drill consists of a cylinder in which works a |>islon carrying a hmg pis- ton-rod. and which is support- ed in such a manner that the drill clamped to the end of the piston - rod alternately strikes atul is withdrawn from the rock as the piston reciprocates back and forth in the cylinder. Means are provided by which the ])iston- rod and drill turn slightly on their axis after each stroke, ' and also by which the drill is imt forward or advanced as the depth of the hole in- creases. As previously stated, there are various special forms of percussion drills, and they difTer from each other chiefly in the methods by which the valve is operated. All of these drills work eitherwilh ilirect steam pressure or with compressed air. Pig. 1 is a longitudinal section showing the interior construc- tion of a conunon form of ])ercussion drill to be operated by steam or compressed air. The steam or air is admitted at A to the chest. B. Prom H the slide valve, C. by moving back and forth ad- mits the steam or air behind first one end and then ihe other of the long-barred piston, D. This >lidc valve is operated by the three-arm rocker, K. which is swung to and fro by the movement of the piston. Workable percussion drills operat- ed by electricity arc built, Ijut so far they do not seem to have been able to coini)ete comnu-rcially with the older forms. Pig. 2 shows sections of an electric drill which has been used to some e.'c- tcnt. The drill is oix-rated by a flexible shaft from a H^ horse-power piutable electric motor. Tliis shaft is attached to a l>evel gear ilriving a crankshaft, .. which passes through the drill- casing. The erankpin works in the slot led hori- zontal arm of the hell-crank lever P. which is mounted on a shaft journahd in Ihe ea-ing. The vertical arm of thc> bellerank straddles the drill- rod, C, and is lilted to trunnions on a casting Fig. 1. CEBcussioN llltlLL.
