Nails, Screws, Bolts, and Other Fasteners - Carpenter's and Builder's Math, Plans, and Specifications - page 37

Figure 1-30 Common toggle bolt.

surface. Removing the screw allows the toggle to drop into the wall
cavity; hence, the unit is easily removed but, in most cases, is not
reusable because the toggle cannot be recovered.
Toggle bolts are commonly available with screw diameters
from

1 3

/ 8 inch and screw lengths to 6 inches, al-
though they can be fitted with screws of any maximum practical

/ 8 inch to

length by using threaded rod. Mini-
mum screw length should equal the
thickness of the object to be fastened,
plus the thickness of the wall facing,
plus the length of the wings when
folded, plus

/ 4 inch. The maximum
length should not exceed the minimum
by much, if at all, or the screw can bot-
tom against the opposite wall facing
and be impossible to tighten.

1

Hanger Bolts, Dowel Screws,
and Toggle Studs
Whenever a hook is to be installed in
a plaster or gypsum board ceiling, it
should be driven through the ceiling
material and into a joist if at all pos-
sible. Since most common ornamental
hooks are supplied with female ma-
chine threads, a device called a hanger
bolt (see Figure 1-31) is necessary to
accomplish this.

Figure 1-31 Hanger bolt
with wood screw threads
at top and machine-screw
threads at bottom.