For more on the nuts and bolts of,
well, Nuts and Bolts, see this article
circumstances. However, you can’t be so
cavalier when installing a sheet-metal screw
into fiberglass because reinforced laminate
will not give like wood. If your pilot hole is
even a few thousandths too small, the screw
will bind and probably break. Here you need
the help of a chart or the accuracy of a caliper,
and always err on the side of the pilot hole
being slightly oversize rather than undersized. In fiberglass you must also chamfer
pilot holes with a countersink bit to prevent
the screws from fracturing the brittle gelcoat
layer. Countersink all fastener holes to be
bedded to enhance the durability of the seal.
Lubricating screw threads with wax, par-
affin, or even soap will make driving new
screws into wood easier. When driving a
self-tapping screw into fiberglass, the usual
thread lubricant is a smear of the chosen
sealant that will be used to bed the screw.
To improve the odds of later being able to
unscrew nuts and machine screws threaded
into tapped holes in steel, use an anti-seize
compound such as those made by Permatex
The most common mistake when installing fasteners is to overtighten them, which
either strips the threads or breaks the fastener. A stainless-steel 10/24 bolt has a
maximum torque of less than 2 foot-pounds
( 22. 8 inch-pounds), a force you can apply
curling your fingers. A 1/4-20 bolt shouldn’t
be torqued beyond about 6 foot-pounds
( 75. 8 inch-pounds). Even the 21-foot-pound
maximum torque of a 3/8-24-bolt requires
only wrist strength to apply. With Harbor
Freight regularly selling torque wrenches for
under $10, there’s no reason not to own
one of these tools if just to gauge your own
strength. Without long experience or the
guidance of a torque wrench, snug threaded
fasteners, then stop.
The keys to fastener reliability are to select
wisely; use lubricant, insulator, or thread
locker when called for; install carefully; and
tighten gently. Do these four things every
time and all your fasteners will deliver their
Ask the Experts member and author Don Casey
has written eight books on boat repair and maintenance including This Old Boat, a comprehensive guide to refitting an older, fiberglass boat.
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