TIMBER FASTENERS AND
As a Builder, be aware that it is usually unnecessary
to call out in working drawings the types of fasteners
used for light frame construction. However, this is not
the case, for heavy timber construction. To prepare
drawings or estimate materials for timber structures,
you need a working knowledge of timber fasteners and
connectors and the manner in which they are used. The
following text covers the more common types.
Bolts used to fasten heavy timbers usually come in
1/2-, 3/4-, and 1-inch diameters and have square heads
and nuts. In use, the bolts are fitted with round steel
washers under both the bolt head and the nut. The bolts
are then tightened until the washers bite well into the
wood to compensate for future shrinkage. Bolts should
be spaced a minimum of 9 inches on center and should
be no closer than 2 1/2 inches to the edge or 7 inches to
the end of the timber.
Driftbolts, also called driftpins, are used primarily
to prevent timbers from moving laterally in relation to
each other, rather than to resist pulling apart. They are
used more in dock and trestle work than in trusses and
building frames. A drifibolt is a long threadless rod that
is driven through a hole bored through the member and
into the abutting member. The hole is bored slightly
smaller than the bolt diameter and about 3 inches shorter
than the bolt length. Driftbolts are from 1/2 to 1 inch in
diameter and 18 to 26 inches long.
Butt joints are customarily connected using
driftbolts; however, another method of making
butt-joint connections is to use a scab. A scab is a short
length of timber that is spiked or bolted to the adjoining
members, as shown in figure 8-42.
A timber connector is any device used to increase
the strength and rigidity of bolted lap joints between
heavy timbers. For example, the split ring (fig. 8-43)
is embedded in a circular groove. These grooves are cut
with a special bit in the faces of the timbers that are to
be joined. Split rings come in diameters of 2 1/2 and 4
inches. The 2 1/2-inch ring requires a 1/2-inch bolt, and
the 4-inch ring uses a 3/4-inch bolt.
Shear plates are shown in figure 8-44. These
connectors are intended for wood-to-steel connections,
as shown in view(B). But, when used in pairs, they may
be used for wood-to-wood connections as shown in
view (C). When making a wood-to-wood connection,
the fabricator first cuts a depression into the face of each
of the wood members. These depressions are cut to the
same depth as the shear plates. Then a shear plate is set
into each of the depressions so that the back face of the
shear plate is flush with the face of the wood members.
Finally, the wood members are slid into place and bolted
together. Because the faces are flush, the members
easily slide into position, which reduces the labor
necessary to make the connection. Shear plates are
available in 2 5/8- and 4-inch diameters.
For special applications, toothed rings and spike
grids are sometimes used. The toothed ring connector
(fig. 8-45) functions in much the same manner as the
split ring but can be embedded without the necessity of
cutting grooves in the members. The toothed ring is
embedded by the pressure provided from tightening a
Figure 8-43.Split ring and split-ring joints.