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Published byStanley Morris Waters Modified over 9 years ago
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Beginning Metal Repair
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Introduction Herb Spenner hspenner@gavilan.edu hspenner@gavilan.edu Background Electrical Engineer – Purdue, A&P – Gavilan College Gavilan Aviation Technology Instructor FAA Airframe and Power (A&P) mechanics program A&P with IA (Inspection Authorization) Teach General & Airframe classes Web based information http://hhh.gavilan.edu/hspenner/BeginMetal/ http://hhh.gavilan.edu/hspenner/BeginMetal/
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Class’s Starting Idea
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Topics Rules & Safety Basic metal properties Cleaning Cutting Drilling & tapping holes Fasteners Welding Finishing
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Projects Drilling and Tapping Cutting bar stock Drilling Tapping Bolt extraction Thread repair (Heli-Coil®)
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Projects Sheet Metal Welding Cutting Cleaning Tack Butt Rosette Flanging Finishing
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Projects Rolling Cart Cutting Cleaning Fitting Welding Joint reinforcement Finishing
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Rules and Safety Safety First! Get instruction on equipment Eye protection and gloves required for all power tools Welding only with a helmet, jacket and gloves Proper Attire No loose fitting cloths Natural fiber cloths Nylon and Polyester will burn Long pants - blue jeans Closed toed shoes No loose jewelry
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Rules and Safety Act Professional Respect the facilities Don’t touch anything in a cabinet without asking Don’t touch any of the students tools Return all Gavilan tools to their proper place Respect your colleagues No eating or smoking allowed in classroom or lab Drinks are acceptable Cleanup after yourself
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Ferrous Metals Ferrous metal is one that contains iron Pure iron is too soft for most uses Add carbon to iron and you get steel SAE - Society of Automotive Engineers SAE four-digit numbering system for identifying steel Hard steel, such as drill bits and taps, break very easily Heat treated, hardened & coated metals are not welded
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CRES Corrosion Resistant steel Stainless steel 10+% of chromium 200 thru 400 series Usually not as strong as carbon steel Usually non-magnetic Difficult to weld
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Aluminum Alloys Soft, lighter and more expensive than steel Aluminum alloy four-digit identification system: First digit - Alloy type Second digit - Modification of alloy Many of the stronger alloys corrode and can’t be welded Work hardens and fails dramatically Steel fasteners will cause aluminum to corrode Paint aluminum or use “sacrificial” washer
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Copper Alloys Alloys Beryllium Zinc – makes brass Tin – makes bronze Aluminum Manganese Corrosion resistant Becomes brittle when work hardened Can’t be welded Braze or solder
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Cleaning Metal All corrosion must be removed before welding or paint Steel corrosion removal Scotch-Brite Sand paper File Grinder Wire brush or wheel Phosphoric acid e.g. Naval jelly
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Cleaning Metal Aluminum corrosion removal Scotch-Brite Very fine sand paper Stain steel wire brush – not used on steel Phosphoric acid wash Copper Scotch-Brite Sand paper File Grinder Wire brush or wheel
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Cleaning Metal Oil must be removed before welding or painting Denatured alcohol Acetone – fingernail polish remover Water test – water will form a film on clean metal If the water film “breaks”, the surface is not clean
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Welding Puddle
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Welding Welding – a process that joins metal by melting or hammering the work pieces until they are united together. Base metal must be melted Process must protect molten metal from atmosphere Material (filler) is added to joint Filler material must match base metal Process must control the amount of heat and the rate that filler is added
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Weld Joints
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Bead
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Welding Gas welding – The use of oxygen and acetylene (oxy-acetylene) to create a flame that melts the metal to be welded Burning process protects metal Uses filler rods Medium hard to learn Portable Dirty Easy to add heat treating and cutting options
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Welding Shielded Metal Arc Welding (SMAW) –– “stick” Arc welding process that uses a consumable flux- coated electrode Flux melts and coats molten metal Forms a glass like cover – must be remove Helps remove impurities Easy to learn Simple equipment Crude results Can be used outside Video Video
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Welding Gas Tungsten Arc Welding (GTAW) – an arc welding process that uses a non-consumable tungsten electrode to produce the heat for the weld. TIG – Tungsten Inert Gas Shielding gas usually is argon or helium Similar to Gas Welding, except uses a electric arc Very clean/very sensitive to dirt Can’t be used in windy conditions Very hard to learn
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Welding Puddle
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Welding Gas Metal Arc Welding (GMAW) – MIG - a method of welding in which the filler metal wire supplies the electric current to maintain the arc, which is shielded from the surrounding air by an inert gas, usually argon or carbon dioxide (CO 2 ) Filler is automatically fed from reel of wire Easy to learn - one handed application Fast Can’t be used in windy conditions Dirty and splatters Difficult to determine the quality of the weld
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Welding Video
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Welding Video 1Video 2
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Welding Flux Core – Combination of “stick” and MIG welding Uses a MIG welding machine Welding wire is hollow with flux inside No shielding gas Easy to learn Can be used outside Dirty
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Welding Spot welding – Uses electric current to fuse two pieces of sheet metal together No filler material Clean Easy to use Extensively used in the automotive industry Video Video
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Weld Joints
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Tack Weld
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Rosette Weld Video
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Drill Bits Sizes available in fraction of an inch, metric and numbered Soft metals – high speed and light pressure Hard metals – low speed and higher pressure Reduce speed a bit size increases Use oil for cleaning chips and cooling
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Tap and Die Tap Die
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Tap and Die Threads UNF – fine UNC – course National Taper Pipe (NTP) Tapered to seal fluids Rolled and cut Rolled is stronger Use matching drill size Use cutting oil and/or grease (catch shavings) 1/2 turn forward and then backup Straight and slow
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Tap
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Plain Washers Provides a smooth bearing surface Protects surface from galling & corrosion Must be used when using a locking washers Should be used under every bolt head and nut When using lock washer, the order should be: Bolt Plain washer Mating surface Plain washer Lock washer Nut
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Metal Cutting Abrasive chop saw Good for bar stock Rough finish Hard to get accurate No oil Angle grinder Cutting wheel – abrasive Wears quickly Grinding disk - shaping Sanding disk - shaping Belt sander - shaping
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Metal Cutting Saws with teeth use oil Hack saw More teeth per inch (TPI) the finer the cutter If careful, can be very accurate Invest in a ridge frame Saber saw Scrolling saw Band saw Shears
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Home Welder Invest in a good helmet MIG best option Be care of “MIG” core flux welders Be care full of combo welders – inexpensive ones may have to many compromises e.g. starter circuits May need “optional” equipment Find one with infinite (smooth) adjustments Is 110 volt enough? – ¼” max welding Cart with good wheels
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Longevity MIG 140
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