# - - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2250) Unit Title: Oxyacetylene WELDING ___________________________________________________________________________ (CLF2256) Topic: Oxyacetylene CUTTING Time Year(s) 5 Hours 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (F-8) - Make a straight cut, using the cutting head. (F-9) - Make a bevel cut, using the cutting head. (F-10) - Pierce a hole in steel plate. (F-11) - Clean the orifices in welding and cutting heads, using the approved technique. (F-13) - Cut sheet metal (14 ga. or thinner) with the cutting head. Special Material and Equipment: Oxygen and acetylene cylinders, regulators and hoses, torch, cutting tips, open-end wrench, tip cleaner, striker, goggles, gloves, cutting material, protective clothing References: Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Resources: Deere & Company. (1987). WELDING (6th ed.) (Fundamentals of Service (FOS) Series). Available from: John Deere Technical Services, Dept. F, John Deere Road, Moline, IL 61265 (Available in Spanish) Evaluation: Quiz by instructor TOPIC PRESENTATION: Oxyacetylene Cutting A. Oxyacetylene Cutting Process and Applications 1. Oxyacetylene Cutting Process: a. Oxyacetylene cutting is a rapid oxidation or burning of metal at high temperature. b. Oxidation is the combining of oxygen with any other substance 1) When oxygen slowly combines with a substance, the process is called oxidation. 2) When oxygen rapidly combines with a substance, the process is called burning. c. This rapid oxidation process is accomplished by gas flame accompanied by a jet action which blows the oxides away from the cut. 2. Oxyacetylene Cutting Applications: a. The process can be applied to all carbon steels up to 0.25% carbon. b. The process can also be applied to higher carbon steels, but only with some difficulty. c. The process cannot be applied to copper, aluminum, or high-nickel alloys. B. Oxyacetylene Cutting Equipment 1. Basic oxyacetylene welding apparatus with a cutting torch attachment is used for cutting. 2. Cutting torch valves: a. Cutting torch (blow pipe) oxygen and fuel valves 1) The fuel valve adjusts the flow of acetylene into the preheat section of the cutting torch attachment. 2) The oxygen valve on the welding torch (blowpipe) is left fully open to supply the attachment with both preheat and cutting oxygen. b. Cutting torch attachment preheat-oxygen valve 1) This valve adjusts the flow of oxygen into the preheat section of the cutting torch attachment. 2) Oxygen is supplied through a different tube than that which supplies the cutting-oxygen valve. c. Cutting torch attachment cutting-oxygen valve 1) This valve injects pure oxygen into the cut when its lever is depressed. 2) The resulting set action greatly increases combustion and removes the molten metal and oxides from the cut. 3. Cutting Tip a. It is designed to accommodate both an oxyacetylene preheat flame and a jet stream of pure oxygen for cutting. b. It has smaller holes surrounding a larger center orifice. 1) The small holes direct the mixed gases into the preheat flame. 2) The larger center orifice permits the jet action of pure oxygen from a separate oxygen tube in the attachment. c. The tip should be cleaned regularly as it becomes clogged with metallic particles during use. 1) Use a tip cleaner that is equal to or smaller in size than the tip holes. 2) Use an up-and-down motion; do not twist the tip cleaner in the tip holes. _________________________________________________________ ACTIVITY: 1. Clean cutting tips with standard tip cleaners. _________________________________________________________ C. Oxyacetylene Cutting Equipment Setup And Operation 1. Cutting Equipment Setup a. Attach the cutting attachment to the welding torch and hand tighten the fittings. b. Select the proper cutting tip size for the job and inspect the taper cone seat to be sure it is not damaged and is free of dirt. c. Insert the cutting tip into the tip nut, screw it onto the cutting attachment, and then tighten it with the appropriate wrench. 2. Cutting Torch Pressurization a. Loosen pressure adjusting screws on the regulators. b. Open the oxygen cylinder valve slowly and completely. c. Acetylene cylinder valve. 1) Open the valve slowly one half turn (one turn maximum). 2) Never use over 15 psi. d. Open the torch (blow pipe) oxygen valve completely. e. Set working pressures according to tip size with the gas flowing. 1) Set the recommended oxygen hose pressure by opening the preheat oxygen valve and adjusting the pressure with the oxygen regulator screw. 2) Set the recommended acetylene hose pressure by opening the torch acetylene valve and adjusting the pressure with the acetylene regulator screw. f. Purge (blow out) the cutting oxygen passages by depressing the cutting torch oxygen lever before lighting the torch. 3. Cutting Torch Lighting and Adjustment a. Open the acetylene valve 1/2 turn and light the torch tip. 1) Add acetylene until the smoke stops and the flame is about 1/8 inch from the tip. 2) Reduce the acetylene until the flame touches the tip. b. Open the preheat oxygen valve on the attachment and adjust to a neutral flame. c. Depress the cutting-oxygen lever and readjust to a neutral flame. 4. Cutting Equipment Shutdown a. Close the preheat valves. 1) Close the preheat-oxygen valve on the attachment first to avoid popping. 2) Then close the acetylene valve on the torch (blow pipe). b. Close both cylinder valves. c. Open the acetylene valve to bleed the acetylene gauges, hose, and torch, and then close it. d. Open the preheat-oxygen valve on the attachment to bleed the oxygen gauges and hose, and to purge the torch. e. Loosen the regulator adjustment screws. D. Oxyacetylene Cutting Procedure 1. Cutting a straight line a. Set the metal to be cut on a cutting table and mark a straight line on it with soapstone or clamp a length of angle iron on the line to guide the tip. 1) For a perpendicular cut, place one side of the angle iron on the surface of the metal so that the other side forms a 90-degree angle to the surface. 2) For a bevel cut, place the edges of the two outside surfaces of the angle iron on the metal surface so the surface aligned with the cutting line forms a 45-degree angle. a. Select appropriate cutting tip size for metal thickness. b. Adjust gas pressures according to tip size selected. c. Light torch and adjust flame. d. Hold the torch with one hand and guide it with the other, keeping the preheat cone 1/16 to 1/8 inch above the metal surface. e. Heat the edge of the metal to a cherry red. f. Depress the cutting-oxygen lever slowly. g. When the cut starts, continue it by moving the cutting tip along the line keeping the preheat cones just above the metal surface. 1) Cutting angle to direction of travel a) For thick metal, the preheat cones are kept perpendicular to the direction of travel. b) For thin metal, the preheat comes are slightly angled in the direction of travel. 2) Cutting speed a) Moving too slow will allow the metal to refuse at the bottom of the cut. b) Moving too fast will cause the metal edges to lose heat and halt the cut. h. If the cut is lost, release the cutting-oxygen lever and reheat the metal before proceeding. 2. Piercing holes a. Preheat the spot by keeping the preheat cones slightly above the metal surface. b. Lift the torch slightly and slowly depress the cutting-cutting lever. c. Tilt the torch slightly to blow the sparks away. d. Continue to feed cutting oxygen onto the spot until the hole is pierced in the metal. _________________________________________________________ ACTIVITY: 1. Identify which metals can be cut with an oxyacetylene torch. 2. Select appropriate cutting tip, gas pressures, flame for metal size being cut. 3. Cut a straight line in 1/8 and 1/2 inch mild steel plate. 4. Make a straight bevel cut in 1/2 inch mild steel plate. 5. Cut sheet metal (14 gauge or less). 6. Pierce a hole in 1/8 inch mild steel plate. _________________________________________________________ 7/1/91 OLR/tf #%&C