Figure 6-2. Electric Drills
cutting tools or to drill heavy stock, both of which require
a slower speed. Therefore, to drill in a metal such as
steel, a 3/8 or 1/2 inch drill should be used, whereas for
drilling holes in wood or sheet metal, a 1/4 inch drill will
Use The operation of an electric drill involves
installing the drill bit and operating the drill.
Installing the drill bit. The drill bit is
installed in the chuck on the drill. Nearly all electric
drills are equipped with a three-jaw chuck, which is
tightened and loosened by means of a chuck key, as
shown in figure 6-3.
· Do not apply further pressure with pliers
or wrenches after the chuck is hand-
tightened with the chuck key.
· Always remove the key immediately after
it is used. Otherwise, the key will fly loose
when the drill motor is started and may
cause serious injury to personnel.
Operating the drill. Stock is drilled as
outlined in paragraph 4-13 of this volume or in TM
Figure 6-3. Three-Jaw Chuck and Chuck Key
Care. Consult the applicable operator's manual
for procedures for maintenance and inspection of
Electric Grinders. To keep hand tools in the best
usable condition, cutting edges must be sharpened
frequently and certain other tools trued or shaped for
special purposes. Chisels, punches, drills, snips,
screwdrivers, and other hand tools are shaped or
sharpened on a grinder. There are two basic types of
grinders: a bench type and a pedestal type. These
grinders, shown in figure 6-4, consist of an electric
motor with a grinding wheel attached to each end of the
motor shaft. One wheel is coarse, for rough work; the
other is fine and is used for sharpening purposes.
Grinding Safety. The grinding wheel is a fragile
cutting tool which operates at high speeds. Great
emphasis must be given, therefore, to the safe
operation of bench and pedestal grinders. The following
procedures are mandatory safety precautions for the
safety of the operator and the safety of personnel in the
Secure all loose clothing and remove
rings and other jewelry.
Inspect the grinding wheel, wheel guards,
toolrest, and other safety devices to ensure that they are
properly installed and in serviceable condition.