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17
h. If the bit jams in the workpiece or if the drill driver stalls, stop the tool immediately. Remove
the bit from the workpiece and determine the reason for jamming.
NOTICE: There are two rules for drilling hard materials. First, the harder the material, the
greater the pressure you need to apply to the tool. Second, the harder the material, the
slower the speed should be. If the hole to be drilled is fairly large, drill a smaller hole rst,
then enlarge to the required size with a larger bit; it’s often faster in the long run than drilling a
larger hole initially.
Wood Drilling
For maximum performance, use high-speed
steel or brad-point bits for wood drilling.
a. Begin drilling at a very low speed to prevent
the bit from slipping off the starting point.
b. Increase speed as the drill bit bites into the
material.
c. When drilling “through” holes, place a block
of wood behind the workpiece to prevent
ragged or splintered edges on the back side
of the hole (Fig. 11).
NOTICE: Bits may overheat unless pulled out
frequently to clear chips from the utes.
Metal Drilling
For maximum performance, use high-speed steel bits for metal or steel drilling.
a. When drilling metals, use light oil on the drill bit to keep it from overheating. The oil will
prolong the life of the bit and increase the drilling action.
b. Begin drilling at a very low speed to prevent the bit from slipping off the starting point.
c. Maintain a speed and a pressure that allow cutting without overheating the bit. Applying too
much pressure will:
–
Overheat the drill driver.
–
Wear the bearings.
–
Bend or burn bits.
–
Produce off-center or irregularly shaped holes.
Fig. 11
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