Figure 2–20Steps to remove rivet
How can a countersunk rivet be removed?
See Figure 2–21.
Figure 2–21Steps to remove a countersunk rivet
What are two ways to pierce steel with OFC?
•Begin by preheating the material in the pierce location to a dull red color, kindling temperature, with the torch perpendicular to the metal. When metal becomes dull red, slightly raise the torch from the surface and angle the tip away from perpendicular. This prevents the slag blown back from the surface from landing on or in the torch tip. Then squeeze the oxygen lever to start cutting action. As soon as the material is completely pierced, restore the tip to perpendicular and the preheat flame to just above the surface. Complete cutting the opening wanted.
•If a small hole is wanted and the surrounding material is to be protected from cutting action, drill a
Figure 2–22Piercing steel
What is the best way to cut out a circle?
Pierce the material inside the circle and away from the finished edge. When cutting action is established, extend the cut into a spiral and begin cutting the circle itself, Figure 2–23. With small circles to avoid damaging the finished edge, drill a
Figure 2–23Cutting a circle
What is the easiest way to sever an I-beam?
Follow the numbered steps in Figure 2–24.
Figure 2–24Severing an “I” beam
What is the AWS designation for oxygen lance cutting?
The abbreviation for oxygen lance cutting is LOC.
What is an oxygen cutting lance and how is it used?
An oxygen lance is a length of steel pipe connected to a source of oxygen. An oxyacetylene welding or cutting torch is used to bring a spot on the work up to ignition temperature. The torch is then removed and the lance pipe end placed over the heated spot and the oxygen supply opened. The lance cuts through the work like a large cutting torch. The steel lance pipe is usually
Figure 2–25Oxygen lance process
Trouble Shooting
What causes a bell-mouthed kerf?
Excessive oxygen pressure, see Figure 2–26.
Figure 2–26Bell-mouthed cut
When the cut is not smooth, how can you determine what corrective action to take?
Compare the defective edge with the drawings in Figure 2–27 to diagnose the problem.
Figure 2–27Cutting Problems and their causes
Air Carbon Arc Cutting
What is the AWS abbreviation for Air Carbon Arc cutting?
The American Welding Society acronym is CAC-A
How does the CAC-A cutting process work?
This process uses an electric arc to melt the metal which is blown away by a high-velocity jet of compress air. See a CAC-A torch in Figure 2–28.
Figure 2–28Air Carbon Arc Torch
Why was this process developed?
Myron D. Stepath originated the process during WW II, while working as a welding engineer with the U. S. Navy, where he conceived the idea to solve the problem of removing defective stainless steel welds in armor plate on warships; the conventional methods, at the time, were chipping and grinding, which had proved infeasible due to time and cost factors.
How is the CAC-A process used?
Today this process is used to rapidly remove defects in welds and base metal.
What are the electrodes made of?
The electrodes are rods made from a mixture of graphite and carbon and most are coated with copper to increase their current-carrying capacity. Manufacturers make both DC and AC rods for this process. See Figure 2–29.
Figure 2–29Carbon electrode air stream and travel direction
What type of power source is required for CAC-A?
Standard constant current welding power sources are used to provide current.
What is the required source of air for this process?
A jet of ordinary compressed shop air is all that is required.
What are the amperage requirements for this cutting or gouging process?
Depending on the electrode diameter and job requirements the amperage ranges can be as low as 60 amperes or as high as 2200 amperes. See Table