Metal Fabrication Agriculture Mechanics II
Purpose of Metal Fasteners • Metal fasteners are made to connect or hold two pieces of metal to each other and include bolts, nuts, washers, screws, and rivets. Taps are used to make threads inside a hole, and dies are used to make threads on round rods or on bolts.
A bolt has a head, shank, and threads. Kinds of bolts include: • 1. Machine bolt is strong and requires a threaded hole in one of the two pieces of metal. • 2. Plow bolt has a tapered head that countersinks into the metal causing the bolt head to be flush with the surface. • 3. Stove bolts are usually small in diameter and may have round or flat heads. • 4. Carriage bolts have a round head and square shoulders that will sink into wood when • wood is fastened to metal. • 5. Hex socket head bolt requires an Allen wrench because it has a recessed hex head. • 6. There are other types of specialty bolts for specific purposes.
A nut is used with a bolt to fasten together metal unless a machine bolt is used with threads in the metal. A slotted or castle nut uses a cotter pin to keep it tight. • To keep nuts from working loose, a lock washer is used between the nut and the metal. • Rivets require a special tool. • Sheet metal screws are self-tapping which means they make their own threads in thin metal.
Using Oxyacetylene Equipment and Materials A. The maximum pressure for acetylene should be 15 pounds per square inch. B. The best and safest tool for lighting an oxyacetylene torch is a friction lighter. Matches and cigarette lighters should NOT be used. C. The proper procedure to check for oxyacetylene leaks is to use soapy water, NOT matches and cigarette lighters.
Using Oxyacetylene Equipment and Materials D. There are different types of tips used for oxyacetylene welding, but the most common is number 5. E. A neutral flame is best for heating, cutting, and welding. F. High carbon steel should be preheated for oxyacetylene welding until the metal is red. G. The white cone from the oxyacetylene torch should not quite touch the sheet metal when welding.
Using Oxyacetylene Equipment and Materials H. The width of the puddle made when welding with oxyacetylene is determined by the penetration and tip movement. I. Proper hand and eye protection should be used for oxyacetylene cutting and welding. J. When transported, oxygen and acetylene tanks should be chained in the upright position.
Welding Various Types of Joints and Metals A. Types of weld joints include: 1. Butt is two pieces of metal lying end to end or edge to edge in the same plane such as flat. 2. Lap is two pieces of metal overlapping each other. 3. Corner is two pieces of metal that make a 90 degree corner. 4. Edge is two pieces of metal placed parallel to each other or stacked on top of each other. 5. Tee or “T” is two pieces of metal placed together to form a T or an upside down T or a T lying on its side. A fillet weld is made in the corner when two pieces of metal are 90 degrees to each other.
Welding Various Types of Joints and Metals B. The filler rod should be the same diameter as the thickness of the metal being welded. C. Butt welds on metal thicker than 1/8 inch should be beveled. D. Pipe welds should start with tacking to hold the two pieces in place. The two methods of pipe welding are roll and fixed.
Welding Various Types of Joints and Metals E. Out of position welds are more difficult than flat position because the puddle metal has a tendency to fall from the puddle making control of the molten metal more difficult. F. A vertical weld should start from the bottom up. G. Different types of filler rods are used depending on the type metal being welded.
Cutting Low Carbon Steel A. A metal container should be used to catch the molten metal to prevent fire hazards and to keep the concrete floor from chipping. B. The proper distance to hold the flame’s inner core from the metal is about 1/8 inch. C. The oxygen lever on the oxyacetylene cutting torch assembly is used to blow the metal from the cut after it is heated to a melting temperature.
Cutting Low Carbon Steel D. Metal cut correctly with an oxyacetylene torch will have the top edge square and the drag lines showing a slight curve. E. Leather gloves and welding goggles should be used to protect hands and eyes. F. Cuffs on pants will collect sparks and cause pants to catch fire.
Cutting Low Carbon Steel G. When starting a cut in the center of a piece of thick steel, drill a ¼ inch hole in the metal beforehand. H. When cutting carbon steel, one should hold the cutting tip 90º to the metal.
Soldering and Brazing Metals A. Soldering and brazing melt only the rod or the solder, NOT the metals being joined. The metal is heated hot enough to melt the rod or the solder. B. Brazing uses a nonferrous filler rod such as bronze and a neutral flame that is above 800 degrees Fahrenheit, but it is below the melting point of the base metal.
Soldering and Brazing Metals C. Soldering uses solder, and metal is cleaned with flux to remove sulfides, oxides, and nitrates. D. Soldering a copper pipe into a copper pipe fitting is called “sweating a joint.”
Soldering and Brazing Metals E. Oxyacetylene or propane torches or soldering irons or soldering guns may be used to heat the metal and melt the solder.
Heating, Bending, Hardening, Tempering, and Annealing Metal A. Heating is done to bend metal thicker than 3/8 inch, and to begin the processes of hardening, tempering, and annealing. B. Metal should be heated to a cherry red heat on the area to be bent before bending.
Heating, Bending, Hardening, Tempering, and Annealing Metal C. Hardening is done by heating to a cherry red heat and plunging the metal in water or oil if high carbon steel. Hardening gives more tensile strength, makes it more brittle, and makes it less ductile.
Heating, Bending, Hardening, Tempering, and Annealing Metal D. Tempering is done to reduce brittleness of hardened steel.
Tempering 1. Uniformly heat the part to be tempered until it is a light cherry red color. 2. Place ONLY the part to be tempered into water and move metal in a circular motion. 3. Take from water and quickly polish the hardened surface with an abrasive cloth.
Tempering 4. When the proper tempering color reaches the end of the piece being tempered, quench the metal. 5. Tools quenched too soon may shatter and crack because they will be brittle. 6. Tools quenched too late will be too soft for use.
Heating, Bending, Hardening, Tempering, and Annealing Metal E. Annealing is heating metal to the proper temperature and then slowly cooling it to soften and toughen hardened or tempered steel. (Annealing reverses the process of hardening or tempering.) To cool slowly, the metal is placed in a container of sand or vermiculite.
Heating, Bending, Hardening, Tempering, and Annealing Metal F. When metal is heated and/or cooled, the characteristics of the metal change.
Using Arc Welding Equipment A. AC welders are usually less expensive than DC or AC/DC welders. B. If an arc welder is used for hard surfacing, a carbon arc torch should be attached to it. C. If only one type of electrode is used for all arc welding, the E6011 is the best choice.
Using Arc Welding Equipment D. Different types and sizes of electrodes are available for different metals and positions. The size of electrodes is determined by the diameter of the electrode on the bare end (metal diameter not including flux).
Using Arc Welding Equipment E. A person making a horizontal or vertical weld should use the position that is most comfortable. F. Safety equipment including a welding helmet with correct lens and leather welding gloves should be worn.
SMAW, GMAW, and GTAW Procedures A. If a bead has slag, the slag should be removed between each pass if a multiple pass weld is used. B. TIG welders have no slag. C. Tacking the ends and center of a weld will help reduce or prevent warping.
SMAW, GMAW, and GTAW Procedures D. Lens should be # 12 or # 14 rather than # 10 for TIG and MIG because the light is brighter than regular arc welding. E. A MIG welder concentrates the heat in a small area. If a person changes from welding aluminum to welding mild steel, the wire and the gas should be changed.
SMAW, GMAW, and GTAW Procedures F. To determine MIG wire feed in inches per minute, the trigger should be squeezed for 15 seconds, the wire measured, and multiply the measurement by 4 because there are four 15 second periods in a minute.
SMAW, GMAW, and GTAW Procedures G. The person should watch the molten metal pool when welding to improve skills (with helmet and proper lens, of course). H. To make a uniform weld on a tee joint, most of the heat should be directed toward the base plate.
SMAW, GMAW, and GTAW Procedures • Welding pipe is difficult because the welding position keeps changing. J. Welding too slowly will make a bead wider, and welding too fast will make it too narrow.
SMAW, GMAW, and GTAW Procedures K. The way to increase or decrease the size of the gas shield and the rate of gas flow for a TIG welder is to change the ceramic cup. L. Carbon dioxide used in GMAW often causes excessive spattering.
Identifying Symbols, Abbreviations, and Numbering Systems Used for Various Metals
AWS means American Welding Society. • 1/2RD means half-round. • A slot or plug weld is indicated by a rectangle, and a fillet weld is indicated by a triangle. • Symbols, abbreviations, and numbers are used to save space on drawings.
Designing a Metal Fabrication Project A. The first procedure in metal fabrication design is to prepare sketches. B. The second step is to review laws and regulations. C. Third step is to determine dimensions and tolerances.
Designing a Metal Fabrication Project D. After checking dimensions, the next step is to prepare drawings, plans, and views. E. The fifth step is to modify plans as needed. F. Base designs on engineered plans that have been tested and proven reliable.
Designing a Metal Fabrication Project G. After the finished design or plan is made, the next step is to select and purchase materials. H. Careful planning at the beginning will save time and money later. • CAD programs make changing a plan much easier than hand drawing.
Using Correct Procedures to Design a Metal Fabrication Project A. It takes a complete set of drawings to have enough information to construct a metal project. B. The scale indicates the size of the drawing compared to the real object. Full scale means that one inch on the project is one inch on the drawing. One inch to 12 inches means that one inch on the drawing is 12 inches on the project. Other scales work the same way.
Using Correct Procedures to Design a Metal Fabrication Project C. Even a simple plan must have dimensions to be of any value. D. CAD, computer assisted drawing, uses a computer, software program, and a plotter to make drawings. E. A good example of drawings should be followed to make usable plans for constructing a metal fabrication project.
Construct a Metal Fabrication Project A. Before beginning construction, a person needs a plan. B. If a design error is found during construction, a design modification is made. C. Welding is the fastest method of metal fabrication. If welding is not the method used, bolting together is the next most popular method.
Construct a Metal Fabrication Project • D. A machinist’s vise is used to hold flat metal for filing, sawing, bending, drilling, etc. A pipe vise is used for round metal and pipe. • E. The frame of a metal project should be made first. The sides should be made after the frame. • F. Safety should be the first concern for all jobs to be observed during metal fabrication.
Construct a Metal Fabrication Project G. A pilot hole is needed if the hole to be drilled is larger than ¼ inch. H. Threads used when making a metal trailer should be bolt threads, NOT pipe threads. A bolt tap is used to thread inside a hole, and a bolt die is used to thread on the outside of a rod.
Construct a Metal Fabrication Project I. When construction of a metal trailer is finished, the trailer should be painted to prevent rust. J. The two diagonal measurements of a trailer should be equal if the trailer corners are square and if the two sides are equal and the two ends are equal.
Construct a Metal Fabrication Project K. Careful planning, measuring, marking, cutting, drilling, and assembly are required to make a metal fabrication project.