the finished weld. Cracked or broken tack welds
plates that are not otherwise accessible for welding.
must be chipped or ground out before the joint is
A plug weld is a circular weld made through one
member of a lap or tee joint to join that member to
finally welded.
another. The plug weld may or may not be through
a hole punched or cut in the first member. If a hole
GROOVE WELDS are made in a specially
prepared groove between two members to be joined.
is used in the first member, the plug weld may fill it
While the edge of a vertical plate of a tee joint is
completely or it may fill it only partially. A slot
sometimes beveled for welding, grooves are most
weld is similar to a plug weld, except that an
frequently used for butt joints in plate and pipe
elongated hole is made in the first member of the
work. Standard grooves for plates joined with butt
joint. The hole may be completely or partially filled
joints are illustrated in figure 7-4. Groove welds are
with weld metal. Slot welds are often used to join
designed to provide the required strength with a
one plate to the surface of another plate, and for
minimum amount of filler metal. Plate edges may
other purposes where a fillet weld would not be
be prepared for groove welding by shearing,
economical or would not be a good design.
machining, chipping, grinding, flame cutting, or
Incidentally, a fillet weld made at the intersection of
flame grooving, depending on the metal. The
the edge of a slot and the exposed surface of the
selection of a particular groove design is governed
joining member is considered a fillet weld, NOT a
by the thickness of the plate to be welded, the
slot weld.
adaptability of the design to the structure, and the
accessibility of the joint for welding. For example,
S P O T WELDS and SEAM WELDS are
a joint that can be welded from only one side
common types of resistance welds. These welds are
requires a different groove design than a joint that
shown in figure 7-6.
In resistance welding,
is accessible from both sides.
coalescence is produced by a combination of
pressure and the heat obtained from the resistance
P L U G WELDS and SLOT WELDS, as
of the base metal to the flow of an electric current.
illustrated in figure 7-5, are used to join overlapping
A spot weld is used only when the parts of the joint
Figure 7-4.--Standard groove welds.
7-7
