TM 9-243
TYPES AND USES
BRACE DRILL
The brace drill is made up of the following parts:
head (1), crank (2), crank handle (3), ratchet
mechanism (4), and chuck (5). The brace is used to drill
holes in wood and with a screwdriver bit, remove and
install screws.
BREAST DRILL
The breast drill is made up of the following parts: breast
plate. (1), drive handle (2), speed shifter (3), side
handle (4), speed gears (5), pinion gears (6), and
chuck (7). The adjustable breast plate provides a base
for the user to lean against while using the drill. The
speed shifter provides a means of selecting high speed
or low speed. This allows the operator to start a hole at
slow speed, 1:1 ratio, preventing marring of the surface,
then shifting to high speed, 3-1/2:1 ratio, to finish drilling
the hole. To change from low speed to high speed, move
the drive handle and speed gears from the bottom hole
to the top hole. High speed position is illustrated. Some
drills have a slot instead of two holes.
The side handle provides a way to steady the drill and
insure that the bit is boring a straight hole. The speed
gears 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 drill
is used to drill holes in wood, plastic, concrete, and small
gage sheet metal.
HAND DRILL
The hand drill is made up of the following parts: handle
(1), drive handle (2), side handle (3) pinion (4), gear
wheel (5) and chuck (6). The handle provides a storage
area for drill bits. The side handle may be used to steady
the drill when drilling in soft wood. The pinion turns the
chuck and drill. Through mechanical linkage, the gear
wheel transfers the driving force from the drive handle to
the chuck. Hand drills are used to drill holes in wood and
sheet metal.
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