- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURE MECHANICS (CLF2350) Unit Title: METALWORKING ______________________________________________________________________________ (CLF2357) Topic: HOT METALWORK Time Year(s) 3 Hours 1 / 2 / 3 / 4 ______________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome # (H-4) - Make square and circular bends in metal, using an anvil or vise. (H-7) - Join metal by riveting. (Supplemental) Special Materials and Equipment: A source of heat to heat and bend metal, preferably a gas fired forge; if not available, an oxyacetylene torch; blacksmith tongs, anvil References: Burke, Stanley R., & Wakeman, T. J. (1990). MODERN AGRICULTURAL MECHANICS (2nd ed.). Danville, IL: Interstate Publishers. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Evaluation: Quiz by instructor and evaluation of lab work and correct shop procedures. ================================================================= *** INSTRUCTORS PLEASE NOTE *** This topic presentation goes beyond the scope necessary to meet the requirements of the Core Cluster in this area. It will take additional time to teach this unit, however, it is included for local enrichment as appropriate to the class. ================================================================= TOPIC PRESENTATION: Hot METALWORK A. Using heat to help soften metal and then using controlled cooling for hardness and stress relief have been done by blacksmiths for many years. 1. Welding was originally done by heating two pieces of metal to a red hot temperature and then hammering the two together on an anvil. 2. Cutting, punching, upsetting (shortening), drawing out (lengthening) are all hot metal procedures used by the blacksmith. B. Hot Metalworking Tools 1. Types of Forges a. Permanent natural gas fired forges are good for heavy metal work and inexpensive to operate. (The original forges used coal.) b. A portable propane fired forge is the best forge for most school shop use because it stores easily and provides ample heat. c. The chimney of the forge is used in order to get a good draft. Ample ventilation must be used with a forge and fire precautions must be taken when using this high heat source. 2. Anvils and Bases a. Anvils are made and purchased by weight. A good size for a shop anvil is 150 pounds. (Some portable anvils are only 60 pounds and other anvils are made for special purposes) such as horseshoeing. b. The anvil base must be of a solid but absorbent material. The best base is made of a large round of oak or other hard wood cut to allow the height of the face of the anvil to be touching the knuckles of a fist when standing by the anvil with the hand held down. Concrete can also be used and is preferred by some. 3. Other Equipment Needed a. Blacksmith's ball peen hand hammer, 1 lb., 10 oz. b. Machinist's hammer, 1 lb., 8 oz. c. Blacksmith's cross peen sledge, 10 lb. d. Machinist's vise e. Hardie to fit anvil, used to cut metal when hot f. Hot cut chisels g. Tongs, straight-lipped, 1/4" opening, 18" length h. Tongs, bolt, 3/8" to 1/2," 18" length i. Water bucket or quenching tank C. Hot Metalwork Procedure 1. Holding the Stock - Because burns are a potential problem with hot metalwork, the correct method of holding the metal is very important. a. Select tongs that fit the work. b. Keep the tongs cool by dipping them in water. 2. Measuring Stock - Use chalk to measure the stock. Use a center punch or file to mark the exact point to be heated. a. For a curved piece of metal, use a light piece of wire to form a shape template and then straighten the wire and measure its length. b. To make a ring, the amount of metal needed is three and a half times the diameter of the ring plus half the diameter of the stock. 3. Heating the Stock - Caution must be used when heating metal in order to avoid having the metal reach a "white heat" stage where it will oxidize or burn. a. Heat should be evenly applied to the entire area to be worked . b. For welding operations, bring like pieces to the same temperature together. c. Determine what amount of heat is necessary to do the job and use no more heat than is needed. 4. Annealing is the heating and slow cooling of metal done in order to soften it and remove stress. a. To anneal iron and steel, heat the stock slowly to a uniform red color and bury the stock in air-slack lime, pulverized charcoal, or wood ashes. b. Remove the metal only after it has completely cooled. 5. Tempering - The hardeness and brittleness of steel for certain purposes is controlled by how it is heated and cooled. Tools such as chisels, hammers, picks, and shears are tempered to last a longer time or maintain their cutting edge. NOTE: Not all steels can be tempered successfully. Use a high quality tool steel for best results. a. To temper, heat the piece of metal to a cherry red color. (Never heat tool steel to higher than a bright red or a low-orange heat or it becomes coarse-grained and weak.) b. Dip the end to be tempered into water while moving it up and down slightly in order to cool the tip rapidly (this will harden the tip). c. Remove the tip from the water while the other part of the metal is still red hot; this allows the heat to creep back into the cooled end. d. Brighten the cooled end immediately with a file and watch for the colors to move back into the cooled end. (See color chart below.) e. When the desired color has just reached the cooled end, immediately plunge the end back into the water and stir the water as before. f. Finally, when the piece has returned to a black color it may be totally submerged in the water for complete cooling. 6. Tempering Color Chart: (Chart shows hardest first.) a. Project: 1) Lathe Cutting Tools Hammers...................Light Straw Color 2) Punches Taps and Dies Drills Reamers Knives....................Dark Straw Color 3) Axes Shears ...................Dark Brown Color 4) Cold Chisels Center Punches Rivet Sets ...............Purple Color 5) Screwdrivers Springs Gears Picks Saws .....................Blue Color 7. Bending and Shaping with Heat a. Heating large pieces of metal that are to be bent allows the metal to work easier and make a sharper bend. b. Correct heating and bending will retain the strength of the metal while it is worked. Never over-heat the metal. Normal heating temperature is reached at a dull cherry red color. c. When using a hammer to form the bend, hit blows hard but as few times as possible in order to prevent a coarse grain from forming as the steel cools. d. Never continue to bend or shape when the color has left the steel. Hammer only when the metal is still red hot. e. Twisting stock can also be done with heat and should follow the same procedures as above. 8. Cutting Metal Hot a. Hot metal may be cut with a hammer and hardie on the anvil as well as with a hot chisel. b. To cut the metal, heat it to a cherry red color and lay it across the hardie at the point it is to be cut. (The hardie goes into the Hardie hole in the anvil.) c. Hit the metal piece with the hammer directly over the hardie and slowly rotate the piece so a groove forms at the point of the cut. When the groove goes entirely around it, hold the piece at the edge of the anvil and strike a sharp blow to break off the excess. d. Lighter stock can be cut directly over the hardie simply by hammering through it. 9. Drawing Out a. Lengthening or slimming a piece of metal is termed drawing out. It is done in the following way: 1) Heat the stock to a white heat. 2) Place the stock on the anvil and use a hammer to strike slight glancing blows. Have the hammer glance off in the direction the stock is to be lengthened. 3) While hammering, turn the stock slightly so it will be hammered evenly on all sides. 4) To change the stock from a square cross section piece to a round cross section piece, first hammer the square to an octagon and then round the corners of the octagon to a round shape. 5) Hammer evenly on all sides and hold the piece at the correct angle to the face of the anvil so the piece will not be bent while it is being hammered. 6) Reheat the stock when it cools below a cherry red color. Do not hammer without color! 10. Upsetting a. Shortening or thickening a piece of metal is termed upsetting. It is done in the following way: b. Heat the part of the stock to be enlarged to a white heat. c. Place the stock in a vertical position on the face of the anvil in order to prevent bending. d. Strike the cold end of the work with hard blows from the hammer. If the piece bends, quickly place it flat on the anvil and hammer out the bend. Continue hammering until the desired shape is reached or the piece has cooled to a dull red heat. Do not hammer without color! 11. Riveting with Heat (an alternative to cold riveting) a. Riveting can be done with or without heat but it is easier done with heat. The process is as follows: 1) Place the rivet into a hole just slightly larger than the diameter of the rivet. 2) With the two pieces of the work held firmly together, the rivet should stick out of the back side of the work by one and a half times the diameter of the rivet. 3) Place the work, with the rivet head down, on the top of the anvil or over a heavy piece of steel. 4) Heat the end of the rivet quickly with a torch or carbon arc to a dull cherry red color. 5) Immediately strike the rivet with a sharp, heavy blow to upset the metal and spread the end. Use a single flat blow which should be ample to size and fix the rivet in place. __________________________________________________________ ACTIVITY: 1. Heat metal to different colors and shape it using the anvil, hammer, hardie, tongs, and gloves. 2. Take a piece of tool steel 7" long, heat it, and form it into a cold chisel. __________________________________________________________ 7/17/91/ YNJ/tf #%&C