great deal of experience to turn out a first-class job. An
example of this method for fabricating a T is shown in
figure 4-28. View A of figure 4-28 outlines the step-by-
step procedures for fabricating the branch; view B
shows the steps for preparing the main section of the T;
and view C shows the assembled T, tack-welded and
ready for final welding.
Step 3 of view A shows the procedure for cutting the
miter on the branch. You should begin the cut at the end
of the pipe and work around until one half of one side is
cut. The torch is at a 45-degree angle to the surface of
the pipe along the line of cut. While the tip is at a
45-degree angle, you should move the torch steadily
forward, and at the same time, swing the butt of the torch
upward through an arc. This torch manipulation is nec-
essary to keep the cut progressing in the proper direction
with a bevel of 45 degrees at all points on the miter. Cut
the second portion of the miter in the same reamer as
The torch manipulation necessary for cutting the
run of the T is shown in Steps 3 and 4 of view B in figure
4-28. Step 3 shows the torch angle for the starting cut
and Step 4 shows the cut at the lowest point on the pipe.
Here you change the angle to get around the sharp curve
and start the cut in an upward direction. The completed
cut for the run is shown in Step 5 (fig. 4-28, view B).
Before final assembly and tack welding of any of
the parts of a fabricated fitting, you must clean the slag
from the inner pipe wall and check the fit of the joint.
The bevels must be smooth and have complete fusion
when you weld the joint.
The cutting torch is a valuable tool for piercing
holes in steel plate. Figure 4-29 shows the steps you
should use to pierce holes in steel plate. First, lay the
Figure 4-29.Piercing a hole with an oxygas cutting torch.
plate out on firebricks or other suitable material so the
flame does not damage anything when it burns through
the plate. Next, hold the torch over the hole location with
the tips of the inner cone of the preheating flames about
1/4 inch above the surface of the plate. Continue to hold
the torch in this position until a small spot has been
heated to a bright red. Then open the cutting oxygen
valve gradually, and at the same time, raise the nozzle
slightly away from the plate. As you start raising the
torch and opening the oxygen valve, rotate the torch
with a slow spiral motion. This causes the molten slag
to be blown out of the hole. The hot slag may fly around,
so BE SURE that your goggles are tightly fitted to your
face, and avoid placing your head directly above the cut.
If you need a larger hole, outline the edge of the hole
with a piece of soapstone, and follow the procedure
indicated above. Begin the cut from the hole you pierced
by moving the preheating flames to the normal distance
from the plate and follow the line drawn on the plate.
Round holes are made easily by using a cutting torch
with a radius bar attachment.
The cutting torch is an excellent tool for removing
rivets from structures to be disassembled. Rivet cutting
procedures are shown in figure 4-30. The basic method
is to heat the head of the rivet to cutting temperature by
using the preheating flames of the cutting torch. When
the rivet head is at the proper temperature, turn on the
oxygen and wash it off. The remaining portion of the
rivet can then be punched out with light hammer blows.
The step-by-step procedure is as follows:
1. Use the size of tip and the oxygen pressure
required for the size and type of rivet you are going to
2. Heat a spot on the rivet head until it is bright red.
3. Move the tip to a position parallel with the
surface of the plate and turn on the cutting oxygen
4. Cut a slot in the rivet head like the screwdriver
slot in a roundhead screw. When the cut nears the plate,
draw the nozzle back at least 1 1/2 inches from the rivet
so you do not cut through the plate.
5. When cutting the slot through to the plate, you
should swing the tip through a small arc. This slices half
of the rivet head off.
6. Swing the tip in an arc in the other direction to
slice the other half of the rivet head off.