Figure 8-7.The first hole cut acts as a guide for drilling
through the floor plate.
In the case of a wall cavity without tire stops or
purlins, the alignment tool is used to snap the bit back
to the inside wail (fig. 8-8) at which time downward
pressure on the drill motor will keep the bit point in
place and cause the shaft to bow. Power and pressure
are then transmitted from the back wall that allows
proper angle drilling to miss the joint boxing.
After the bit has penetrated into the basement area,
as shown in figure 8-9, the operator has access to the
hole in the drill bit itself for attaching the recovery grip
Figure 8-8.Alignment tool used to snap the bit back to the
Figure 8-9.Bit has penetrated into basement area.
and pulling the wire up to the outlet location-all
without damage to existing finishes.
Figure 8-10 shows how the recovery grip is
attached to the bit tip eyelet. The swivel, located
between the cable and the head of the grip, prevents the
wire or cable from becoming twisted during the fishing
Figure 8-11 shows the grip after it has been
attached to the bit tip with the line inserted, ready for
recovery. The operator uses the drill motor in reverse
and applies a slight pull. The wire then can be pulled
easily through the holes because of the reverse cutting
action of the bit. If desired, the drill motor can be
removed from the shaft and a recovery grip attached to
the chuck end of the shaft for pulling the wires
downward toward the basement. While this example
shows the method of routing wires or cables from an
outlet to a basement, the same procedure would apply
for drilling from an outlet opening to an attic space.
To install contacts on windows for a burglar-alarm
system, drill from the location of the contact through
the casement, lintels, and plates with a 3/8-inch (0.9-
cm) shaft. Attach a recovery grip to the end of the bit,
insert the wire to keep the grip from becoming tangled,
reverse the drill motor, and bring the wire toward the
operator as the bit is being withdrawn.
Burglar-alarm contacts or door switches installed
at doors are simple projects when one uses the flexible
shaft. First cut or drill the entrance hole in the normal
manner and then insert the flexible shaft with bit into