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 necessary 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 first.
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 cut.
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 slowly.
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.Continue Reading