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LAP WELDS
LAP WELDS
Figure _14
Figure
15
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should be nearly flat with a slight radlus at the SidesOr
wilL come: with experience, ffthe
arc is advanced too fast,
toes. AVoid excessive concave or convex surfaces of the
held:t6o: close to the vertical plate,
undercutting may
fillet (fig: 7): UnderCuts and Cold-laps are caused by not
holding the rod in the cen_r! 0f the :seam: (fig; 8). ff the
desired fillet weld cannot be ma_e with a Sing!e pass,
several passesare used to build it up to required size (fig_ 9).:
Slag must be cleaned from each pass before depositing
the next. Fillet welds over 1!2dnch in size a_e rarely used
because ioints requiring
more strength can be made more
economically by beveling and groove-welding0
followed
by a small concave fillet weld to provide a radius in the
corner,
Horizontal
fillet
welding
is used when the side or edge
of
one member
of the joint is in the vertical
position particularly
for small
single-pass
welds where the work cannot be tilted,
Far
practice,
tack-weld
two pieces
of scrap
together
to
form
a tee-joint
(fig.
10).
Use a 5/32-inch
rod
held
at
angles
indicated,
and direct the arc
into the corner
of the
joint. The arc _ength
should
be somewhat
shorter than for
fiat
fillet
wetding.
To assure penetration
at the root,
use the
highest
welding
current
that
can
be
handled
(fig.
11).
Good
penetration
is of prime
importance
and appearance
result (fig. ]2).::Toostow
trove] will cause oVerlapping and
an extremely close arc or low current will produce a bead
_iith a convex surface (fig. 13). To check the penetration and
soundnessof the bead, break some of the Weldi_for inspec-
tion, as shown in figure 4.
When making a lap weld, care should be taken not to melt
too much Of the upper corner on the top plate (fig. 14).
sorine melting wil! take place, but proper advance of the
rod will cause the weld metal to build up and blend into the
top surface. On sheet metal, hold the 3/32-inch rod almost
perpendicular and move the arc rapidly.
Welds
of this
type should be wider than they are high, somewhat like
flat bead (fig. 15). A slight discoloration
on the underside
of the lower sheet indicates good penetration.
On heavy
metal, (: 3/8-inch
fillet weld can be laid in one pass with a
1/4-inch
rod using a 295-ampere
machine. However, with
smaller machines, the same weld or larger can be made by
building
up with a number
of passes (fig:
16}. When
welding
long narrow
pieces, stagger the welds
in short
intermittent
beads, first on one side then on the Other side,
to minimize distortion
(fig. 17).
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