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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