Figure 7-21.Use of backing strips in welding butt joints.
For plates up to 3/8 inch thick, the backing strips should
be approximately 1 inch wide and 3/16 inch thick. For
plates more than 1/2inch thick, the backing strips should
be 1 1/2 inches wide and 1/4 inch thick Tack-weld the
backing strip to the base of the joint, as shown in figure
7-21. The backing strip acts as a cushion for the root
pass. Complete the joint by welding additional layers of
metal. After you complete the joint, the backing strip
may be washed off or cut away with a cutting torch.
When specified, place a seal bead along the root of the
Bear in mind that many times it will not always be
possible to use a backing strip; therefore, the welder
must be able to run the root pass and get good penetra-
tion without the formation of icicles.
Figure 7-22.Horizonta1 groove weld.
Figure 7-23.Horizontal fillet weld,
You will discover that it is impossible to weld all
pieces in the flat position. Often the work must be done
in the horizontal position. The horizontal position has
two basic forms, depending upon whether it is used with
a groove weld or a fillet weld. In a groove weld, the axis
of the weld lies in a relative horizontal plane and the face
of the weld is in a vertical plane (fig. 7-22). In a fillet
weld, the welding is performed on the upper side of a
relatively horizontal surface and against an approxi-
mately vertical plane (fig. 7-23).