- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURE MECHANICS (CLF235) Unit Title: METALWORKING _____________________________________________________________________________ (CLF2355) Topic: SHEET 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-2) - Identify ten common metalworking tools by type and use. (H-3) _ Layout a drawing on metal. (H-4) - Make square and circular bends in metal, using an anvil or vise. Special Materials and Equipment: Layout tools, sheet metal working tools, two pieces of 24-28 gauge galvanized sheet metal for each student 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 sheet metal layout to finished project TOPIC PRESENTATION: Sheet METALWORKING A. Sheet metal Tools 1. Cutting Sheet metal a. A cold chisel is used with a hammer and a vise to shear the metal when only the piece in the vise is to be saved. b. Tin snips are available in several sizes and jaw shapes; they are used to cut metal as thick as 20 gauge by hand. c. A hand notcher removes a small notch from the edge of a piece of metal in order to allow the metal to be bent in a circle to the inside or to the outside. d. A hand punch is a 'C'-clamp shaped tool which uses an inside punch and outside die to cut holes in sheet metal. The size can quickly be changed to the desired diameter. e. Aircraft shears or compound snips come in right hand cut, left hand cut, and straight cut depending upon the shape being cut. They make use of compound leverage action for easy cutting and have a slightly serrated cutting edge to grip the metal. f. A squaring shear is a foot operated cutting shear which will cut a full width sheet of metal in one cut. It is used to make long cuts and produce smaller pieces for use as projects. 2. Bending and Folding Tools a. A setting hammer is a small 6-8 oz. hammer with a square-shaped face on the head and a sloped or slanted peening end used to close sheet metal down around a wire. b. A tinner's bench plate and stakes consists of a large, heavy plate of cast steel with a series of square holes that accept many different kinds of shaping stakes used in bending and forming sheet metal. c. A hand seamer is a pliers-like tool with long, flat, smooth jaws that grip the sheet metal in order to fold it over or partially bend it. d. A hand crimper shortens one side of an angle in order to allow it to be curved to the inside. e. A sheet metal brake is a hand- or foot-operated bending machine that is wide enough to allow large pieces of sheet metal to be bent at one time along a single line. It can usually bend up to 120 degree angles. f. A sheet metal roll former is a hand-operated machine that uses three rollers to bend the metal around itself to form a tube, a ring, or a curved metal piece. B. Sheet metal Layout 1. Project Selection a. Select a simple project such as a small tray or box. b. Include in the project seams, hems, tabs, holes, folds (bends), and notches. c. Use a thin gauge metal to make the project (24-26 gauge). d. Draw the project on paper, then cut out and fold the paper template before doing the project in metal. e. When the paper template is correct, place the template over the sheet metal and tape it down. Using the awl, prick a small indentation through the template and into the metal at each intersecting point of lines. This forms a "dot-to-dot" on the metal which can then be connected with the scriber to form the outline and bend lines of the project. f. Finish the project by soldering all the tab joints so they are watertight when tested. 2. Simple Project for Sheet Metal Layout ________________________ ...................../........................\ ..1/4" hem : | | 1.5" | | :.... ______ | bend up | ______ _______ 1/4" .. ./.......\|..........................|/......\/.... ..\..tab : | : : : | : | b b b | : | e LAYOUT OF e e | : | n n n | 3" | d PARTS BOX d d | : | : : : | : | : : : | : |<-1.5"-> <---------5"-----------> <-1.5"-> <--1"-->| : | : : : | :..........|........:..........................:........:........| 1/4" \______/| bend up |\______/\_______/..tab : | | 1.5" | | :...................|..........................| \________________________/ ..1/4" hem NOTE: Use full-scale layout for all drawing and transfer work in sheet metal. C. Cold Metal Riveting 1. Riveting can be done with or without heat. Cold metal riveting is used with small rivets and/or small riveting jobs. The process is as follows: a. Mark, center punch and drill a hole slightly larger than the diameter of the rivet. b. Load the rivet into a pliers-type pop-riveter being sure that the rivet is tightly held. c. Place the free end of the rivet through a pre-drilled hole and squeeze the handle of the pop-riveter. (It normally requires two (2) squeezes of the handle to properly set the rivet.) d. The rivet can be flattened by placing the project on an anvil and striking it with a ball peen hammer. 2. Soldering Process a. Cleaning - Since soldering is an alloying process, the base metals must be very clean in order for the solder to adhere to the surface of the metal. 1) Pre-clean with steel wool, wire brush, or emery cloth. 2) Use a 50% solution of muriatic acid and water in order to remove grease, wax and metal oxides from the base metal. (Caution: Eye protection and other safety procedures should be followed when soldering or preparing to solder.) 3) Acid and/or rosin flux are used during soldering for the following reasons: a) They remove any final oxides of the base metal just before soldering. b) They prevent or minimize oxidation while the base metal is being heated. c) They aid in the flow of heat to the base metal and protect the solder from oxidation while it is molten. 4) Note:: Wash sheet metal with water when finished soldering in order to remove any traces of acid or flux and to prevent metal corrosion. b. The base metal pieces must be heated to just above the melting point of the solder and kept at this temperature while the soldering is being done. 1) A light coat of solder is sometimes applied to the surface of the metal and rubbed along with steel wool to tin the surface before going back and completely soldering the joint. 2) Several sources of heat may be used to solder: a) Blowtorch and soldering copper b) Electric soldering iron c) Propane hand torch bottle d) Electric soldering gun (usually used for small work) 3) Heat evenly and feed the solder into the metal at the point of application of the heat. (The molten solder will seek the heat and capillary action will draw the solder into the joint.) _______________________________________________________________ ACTIVITY: 1. Practice cutting, drilling, and bending sheet metal. 2. Practice cold riveting on sheet metal. 3. Design and build a simple sheet metal project such as bookends or a coal scoop. _______________________________________________________________ 7/17/91 CC/tf #%&C