How does flux cutting work?
Flux cutting uses a granular flux introduced into the oxygen cutting stream. The flux combines with the alloying metals’ oxides to lower their melting temperatures to near those of iron oxides and get them to flow out of the kerf. Flux cutting can eliminate torch oscillation and can increase cutting speeds in stainless to that of carbon steel of the same thickness.
Tips, Techniques, and Helpful Accessories
Why is it important to keep the torch tip face clean and flat and to clean out the orifices with tip cleaners regularly?
A damaged tip face or plugged tip orifice can cause an unsymmetrical flame. Such a flame will produce irregular rough edges, and slow cutting action. Dirt inside the torch tip may cause flashbacks.
What are the two best ways of marking the line of cut?
•With welder’s soapstone.
•By a series of center punch marks along the line of cut.
What readily available material may be used to improve the quality of some cutting tasks?
Angle-iron may be used as a straight edge guide, or as a bevel guide. See Figure 2–10.
Figure 2–10Angle iron used as a straight edge (left) and bevel guide (right)
What are two mechanical aids that can be attached to a cutting torch?
•Wheels to keep the torch tip at a constant height above the work and reduce operator fatigue. See Figure 2–11.
Figure 2–11Torch wheels
•Compass attachment to make nearly perfect circles easily. See Figure 2–12.
Figure 2–12Compass attachment
Name the four main types of electrical or electronic aids to guide a cutting torch to increase the accuracy and quality of cutting.
•The motorized cutting head is the most primitive improvement over a handheld torch. Its wheel is motor-driven to maintain optimum cutting speed; the wheel also keeps the torch-to-work distance constant. However, the welder must still guide the motorized head manually. The small wheel in the rear of the unit is useful for cutting accurate bevels. See Figure 2–13.
Figure 2–13A motorized cutting head
•A portable track cutting machine travels along a pair of steel rails driven by a 120 VAC motor. It can make 90° bevel angle and chamfer cuts. It also cuts circles from 4 to 96 inches (0.1 to 2.4 m) diameter. With a second torch, it makes two parallel cuts simultaneously to produce a strip of metal with two parallel edges. It is especially useful in cutting accurate bevels and chamfers for proper fit up. See Figure 2–14 and 2–15.
Figure 2–14Portable track cutting machine
Figure 2–15Two-torch strip cutting attachment for portable cutting machine
•A pattern tracer is the next level of improvement. A stylus follows the edge of a metal pattern, or a photoelectric eye follows the lines on paper and a torch (or could be multiple torches) is directly connected to the pattern tracing mechanism, permitting the torch to reproduce the pattern shape in steel. These systems require heavy cutting operator involvement and supervision.
•Computer driven cutting machines produce the most accurate and best quality cuts. These machines store the path of the cutting torch in their memories. Advanced machines control torch-to-work distance, adjust the torch speed on curves and around corners, adjust the pre-heat and cutting flame to starting and ending cuts. The most sophisticated machines require only loading raw stock and removing scrap and finished parts and can pierce holes to make inside cuts without operator assistance.
What degree of dimensional accuracy can be maintained in cutting machines?
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How should you adjust the torch tip preheat orifices in a normal cut?
If there are two preheat orifices, the tip should be rotated in the torch so that a line drawn between orifices will be perpendicular to the cut line. If more orifices, two should fall on the cut line and the rest divided equally on each side of the cut line. This symmetrical preheating improves the quality of the cut. See Figure 2–16.
Figure 2–16Location of preheat orifices in relation to kerf for a normal cut
For making a bevel cut how should you adjust the preheat orifices?
See Figure 2–17.
Figure 2–17Location of preheat orifices in relation to kerf for a bevel cut
What is the best torch technique to start a heavy cut?
See Figure 2–18.
Figure 2–18How to start a cut on heavy steel
What are the proper terminating conditions when making a heavy cut so as not to let the effect of drag permit the cutting action to skip a small triangular area at the bottom of the end of the cut?
As the end of the cut nears, tilt the torch away from the direction of travel. This permits the bottom of the cutting action to proceed ahead of the top cutting action and eliminates premature breakout of the flame which leaves a triangle at the end of the cut. See Figure 2–19.
Figure 2–19How to complete a cut on heavy steel
What is the easiest way to remove a rivet with