GENERAL INFORMATION
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the normal way. If the screw head is too damaged to use this method, grip the head with locking pliers
and twist the screw out.
Avoid applying heat unless specifically
instructed. Heat may melt, warp or remove the temper
from parts.
Removing Broken Fasteners
If the head breaks off a screw or bolt, several
methods are available for removing the remaining
portion. If a large portion of the remainder projects out,
try gripping it with locking pliers. If the projecting
portion is too small, file it to fit a wrench of cut a slot in
it to fit a screwdriver (Figure 35)
If the head breaks off flush, use a screw extractor.
To do this, center punch the exact center of the
remaining portion of the screw or bolt. Drill a small
hole in the screw and tap the extractor into the hole.
Back the screw out with a wrench on the extractor
(Figure 36)
Repairing Damaged Threads
Occasionally, threads are stripped through
carelessness or impact damage. Often the threads
can be repaired by running a tap (for internal threads
on nuts) or die (for external threads on bolts) through
the threads (Figure 37). To clean or repair spark plug
threads, use a spark plug tap.
If an internal thread is damaged, it may be
necessary to install a Helical or some other type of
thread insert. Follow the manufacturer’s instructions
when installing their insert.
If it is necessary to drill and tap a hole, refer to
Table 8 for metric tap and drill sizes.
Stud Removal/Installation
A stud removal tool (Figure 38) is available from
most tool suppliers. This tool makes the removal and
installation of studs easier. If one is not available,
thread two must onto the stud and tighten them
against each other. Remove the stud by turning the lower nut (Figure 39).
1. Measure the height of the stud above the surface.
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