TM 9-243TYPES AND USESBRACE DRILLThe brace drill is made up of the following parts:head (1), crank (2), crank handle (3), ratchetmechanism (4), and chuck (5). The brace is used to drillholes in wood and with a screwdriver bit, remove andinstall screws.BREAST DRILLThe breast drill is made up of the following parts: breastplate. (1), drive handle (2), speed shifter (3), sidehandle (4), speed gears (5), pinion gears (6), andchuck (7). The adjustable breast plate provides a basefor the user to lean against while using the drill. Thespeed shifter provides a means of selecting high speedor low speed. This allows the operator to start a hole atslow speed, 1:1 ratio, preventing marring of the surface,then shifting to high speed, 3-1/2:1 ratio, to finish drillingthe hole. To change from low speed to high speed, movethe drive handle and speed gears from the bottom holeto the top hole. High speed position is illustrated. Somedrills have a slot instead of two holes.The side handle provides a way to steady the drill andinsure that the bit is boring a straight hole. The speedgears determine the speed at which the drill rotates.They are connected through linkage to the pinion gears.The pinion gears turn the chuck and drill. The breast drillis used to drill holes in wood, plastic, concrete, and smallgage sheet metal.HAND DRILLThe hand drill is made up of the following parts: handle(1), drive handle (2), side handle (3) pinion (4), gearwheel (5) and chuck (6). The handle provides a storagearea for drill bits. The side handle may be used to steadythe drill when drilling in soft wood. The pinion turns thechuck and drill. Through mechanical linkage, the gearwheel transfers the driving force from the drive handle tothe chuck. Hand drills are used to drill holes in wood andsheet metal.23-2
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