Figure 3-16.Fillet welds.
Figure 3-17.Surfacing welds.
After the effects of heat on metal are discussed, later
in the chapter, you will understand the significance of
the buildup sequence and the importance of controlling
the interpass temperature.
Across-sectional view of a fillet weld (fig. 3-16) is
triangular in shape. This weld is used to join two sur-
faces that are at approximately right angles to each other
in a lap, tee, or comer joint.
Surfacing is a welding process used to apply a hard,
wear-resistant layer of metal to surfaces or edges of
worn-out parts. It is one of the most economical methods
of conserving and extending the life of machines, tools,
and construction equipment. As you can see in figure
3-17, a surfacing weld is composed of one or more
stringer or weave beads. Surfacing, sometimes known
as hardfacing or wearfacing, is often used to build up
worn shafts, gears, or cutting edges. You will learn more
about this type of welding in chapter 6 of this training
A tack weld is a weld made to hold parts of an
assembly in proper alignment temporarily until the final
welds are made. Although the sizes of tack welds are not
specified, they are normally between 1/2 inch to 3/4 inch
in length, but never more than 1 inch in length. In
determining the size and number of tack welds for a
specific job, you should consider thicknesses of the
metals being joined and the complexity of the object
Plug and slot welds (fig. 3-18) are welds made
through holes or slots in one member of a lap joint.
These welds are used to join that member to the surface
of another member that has been exposed through the
Figure 3-18.Plug and slot welds.
hole. The hole may or may not be completely filled with
weld metal. These types of welds are often used to join
face-hardened plates from the backer soft side, to install
liner metals inside tanks, or to fill up holes in a plate.
Resistance welding is a metal fabricating process
in which the fusing temperature is generated at the joint
by the resistance to the flow of an electrical current. This
is accomplished by clamping two or more sheets of
metal between copper electrodes and then passing an
electrical current through them. When the metals are
heated to a melting temperature, forging pressure is
applied through either a manual or automatic means to
weld the pieces together. Spot and seam welding
(fig. 3-19) are two common types of resistance welding
Spot welding is probably the most commonly used
type of resistance welding. The material to be joined is
placed between two electrodes and pressure is applied.
Next, a charge of electricity is sent from one electrode
through the material to the other electrode. Spot welding
is especially useful in fabricating sheet metal parts.
Seam welding is like spot welding except that the
spots overlap each other, making a continuous weld