welding sheet metal repairs

Discussion in 'Welding Tips and Welders' started by grumpyvette, Dec 9, 2010.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    watch the video for the basics
    a decent tig welder and a few air tools and knowing what your doing goes a long way!

    http://www.weldingtipsandtricks.com/wel ... video.html

    http://www.bapspaint.com/docs/psheets/P ... /P-226.pdf

    By John Kelly/Ghia Specialties

    When welding a patch panel or fender flare on a car, I use either oxy-acetylene (gas welding) or wire-feed (mig welding), in that order of preference. Tig welding is great, but few do-it-yourselfers have a tig welder, so we’ll stick with the first two. Gas welding is my first choice because the metal stays fairly soft and workable, and metal-finishing is easier (and more quiet). Mig welding work-hardens the metal and seems to shrink the weld area excessively. Gas welding also shrinks (heat shrinks); however, the metal is still workable with hammer & dolly, whereas a mig-welded panel is too stiff to work effectively.

    Gas Welding: As a good rule of thumb, gas-weld the panels you can reach both sides of; mig-weld where access is more limited. I sometimes do both on a panel. If you choose this method, be aware that it’s easier to mig-weld over a gas-weld than vice-versa, so do the gas-welding first (at least where the welds join). When gas-welding, I use the smallest tip I can get away with, usually a 00 or 000, and low line pressures. If the torch pops when welding, the pressure may be too low, the tip may be too large, or the tip may be dirty. If the torch is noisy, the problem might be, high line pressure, too small a tip, too much oxygen, a dirty tip, or a combination of these.

    Your weld-puddle should look smooth and glassy. If your weld falls through, you’re too hot; if it takes more than a few seconds to get a puddle going, you’re too cold. If your torch acts up once you’re set up the way you like, the problem is usually a dirty tip. Try welding two pieces of 20 gage steel together. Connect the pieces together edge-to-edge (butt weld). If your heat is right and you have a perfect fit, you can fusion-weld them. Fusion-welding is basically melting the metal together, without using filler-rod. You can make beautiful little welds this way. I usually fusion-tack my panels together and use a little filler-rod when finish-welding, to keep from having a concave (shallow) weld surface.

    Check the back-side of your weld to make sure you’re getting good penetration. It should look like a weld, not two edges glued together. If you didn’t get good penetration, you can fusion-weld over the bad spots from the back. This exercise will help you make good welds later, when you can’t see the back-side of your work. Remember, heat shrinks, so stretch your tacks with a hammer & dolly; the same applies when finish-welding. After 1/2” to 3/4” (as you get more experienced, you may decide to weld several inches at a time), set your torch down (turned off or in a safe holding bracket), and use your hammer & dolly. The object is to remove some of the shrinking you’ve caused by welding, while keeping your panel in shape. Don’t stray too far from the weld to begin with. You’ll find you can get your shape back if you patiently work the weld area first, and then address any peripheral warpage. Remember, if your panel fits well to begin with, you should be able to make it fit when you’re finished, without resorting to drastic measures. Here is an excerpt from the directions that I send out with my shrinking disc. This may help a little with metal-finishing:

    Dent repair and metal-finishing: To repair a dent, use a dolly to bump up the low spot from behind. Some larger dents are best worked from the perimeter in. Bumping with a dolly will bring the dent back near the original contour. This simple step is important throughout the repair, because, in addition to the inevitable small areas that need minor stretching later in the process, you will probably find low spots that just need bumping up. After bumping the dent up to its original contour, start working the metal off-dolly. This means pushing up with a dolly on low spots while hitting high spots with a hammer or slapper. This will start to get the panel smoother. Now start some medium-force on-dolly work. Usually, on-dolly work is stretching the metal between the hammer and dolly but, in this case, very little stretching is done, especially if you use a slapper instead of a hammer, as the force of the blow is spread more evenly. You are using multiple hits to planish (smooth) the area. Now check the shape of the panel. Use templates taken from the same spot on the other side of the car wherever possible. Use one up and down, and another front to back to see where the shape is too low or too high. Sometimes the whole area will still be too low and need more bumping and hammer-and-dolly work. Once you are satisfied that the general shape is right, you can start to pick up specific low spots by stretching on-dolly. Use a dolly that has a slightly higher crown than the panel being worked, and a hammer with a slight crown in it. This way there is a small contact area between the hammer and dolly, making it easier to stretch small areas up. You must push up fairly hard on the dolly. You should see small marks on the metal where it is stretched by the blows. Lightly file the area to show the highs and lows, then repeat the hammer-and-dolly steps, and file lightly again until you have the whole area smooth but a little too high. As an alternative to stretching up the low spots with a hammer and dolly, a tool called a bullseye pick [available from Ron Covell on my links page] can be modified to work very well. It is a little easier to use and may be easier on your arms if you have a lot of work to do. The tip must be ground down so that it is not so sharp, otherwise it will damage the panel. A tip I picked up from Wray Schelin: During metal-finishing, use a large magic marker (“Magnum” size) to ink the whole repair area before filing. This really makes the low spots stand out, just like using a guide coat for sanding primer. For more about metal-finishing from a different perspective, please see the Jag Lovers articles written by Wray Schelin, also on my links page. “The Key to Metal-Bumping” by Frank Sargent is a good resource booklet as well. (The above mentioned links are on the links page of the http://www.ghiaspecialties.com site.)

    Using the shrinking disc: Once you have the metal smooth but high, start running the disc over the surface, back and forth, while moving sideways slightly after each pass - basically a zig-zag pattern, much like what you would use when conditioning a panel with a sander. For most applications, a 6” x 6” area of coverage is a good starting point. Small high spots will turn blue. Stop immediately and use a wet rag to quench and cool the metal. Do not rush! There is no hurry. I keep a rag in the bottom of a bucket with about an inch of water in it so it doesn’t splash much when I drop the rag in after use. The smoother the panel is, the longer you can run the disc without turning any part of the panel blue. It is not necessary to use the disc until the metal turns blue in order to shrink; use it just long enough so that when you quench it with a wet rag it steams. This will take practice to gain the experience of knowing when to stop. Run your hand over the metal both up and down and back and forth to feel the surface while it is still wet. You will be able to tell where the high spots are, and use the disc for a shorter period of time to shrink specific areas. The disc will mark the metal and show the low spots as unmarked. Do not hesitate to go back to some of the previous steps of on-dolly stretching or using the bullseye pick to raise low spots. You may find it necessary to bump up some low spots, or even go back to some off-dolly work. This is part of the process. Once you have done an operation, never assume that it can’t be the problem. Always let the panel dictate what needs to be done. Most severe damage will require multiple passes of the shrinking disc interspersed with quenching, hammer-and-dolly work, and/or the bullseye pick. Once you have the panel nice and smooth, you can spray a guide coat on it, or use the Magnum marker, then sand with an appropriate sanding block with 80 grit to help show small discrepancies. At this stage, you can use a worn-out Scotch Brite pad on a 7” Velcro backing pad fitted to your sander, just as you would the shrinking disc, then quench, to simultaneously polish the surface and shrink a little more as well.

    Mig Welding: Most people who have just started mig-welding, seem to have a hard time seeing the weld as they go. If you’re having this problem, make sure the clear lenses protecting your weld lens are new. Also, try using the trigger to do a puddle, then let go of the trigger, move the gun slightly, and repeat this process over and over as you move along. This way, you won’t feel like the machine is forcing you to go too fast. You may find this method helps the quality of your welds, too.

    Don’t hesitate to play with the weld settings on your machine; that’s what they’re for. Is your gun jumping? …getting lots of sparks? Your wire speed is probably too high in relation to the voltage. Blowing holes in your work (even with the stop & start method described earlier)? …welds look like lava flows? Your voltage is probably too high, in comparison with your wire speed, or your voltage and wire speed are both too high. Lumpy-looking welds? You should be welding hotter (more wire speed and voltage).

    Tack Welding: Take your time, and use lots of tacks; not only do they hold your panel in place, they also help dissipate the heat evenly. The best results are achieved when you insert the panel flush with the car body, instead of overlapping, and less grinding and filler will be required. If you have to push the panel into place to tack it, you will have more of a problem with distortion than if you make the panel fit better to begin with. Tack about every inch or so. If you grind the tops off the tacks, you may have an easier time making a good final weld.

    Finish Mig Welds: When doing your final welding, weld only one small hot tack at a time. Do not weld in an area that is warm to the touch. The more heat you put in one place with a mig welder the more leverage the warpage has. When finished, grind the weld as smooth as possible, then sandblast the area. If you don’t have a sandblaster, carve all the scale out of the welds using a small broken drill bit held at an angle in your drill motor. You want shiny metal. When you need filler over welds (usually the case with mig-welding), your first application should be a fiberglass-reinforced filler, as it is tougher and shrinks less than regular filler.

    Some Final Tips: Use templates on any shape that isn’t flat. Take the time to protect your eyes, ears, and lungs. Keep a fire extinguisher handy, and keep a fire watch on your shop at least ½ hour after welding.

    I wrote this because I was unable to find out most of this information when I was starting out. I hope it will be helpful to someone. This article states my opinions and is not the gospel, as I’m sure others may have different ideas when it comes to some of this stuff. Get to work! Updated March 2003.

    Address questions about his shrinking disc, or this article to John Kelly at: ghiaspec@ghiaspecialties.com
    Last edited by a moderator: Mar 21, 2021
  2. grumpyvette

    grumpyvette Administrator Staff Member

    Successfully Welding Sheet Metal With MIG And TIG

    For fabricators and others with bottom line goals, welding sheet metal often means a constant battle between productivity and equipment investment vs. burn-through, warping, excessive heat affected zones (HAZ) and weld appearance. For the individual occasionally welding sheet metal, success can be as simple as learning the proper techniques.

    Process Selection

    When welding thin metal, the main objective is to avoid warping, burn-through and excessive heat affected zones while still ensuring the weld has sufficient mechanical strength for the application. The welding processes that provide the most control over heat are short circuit transfer GMAW ("short arc"), pulsed GMAW, GTAW and pulsed GTAW.

    Process-Specific Advice

    GMAW Electrode and Shielding Gas Selection
    Use the smallest wire diameter feasible. A smaller wire takes less heat to melt, which in turn heats the metal less. A smaller wire also gives you more control over the weld bead and a better chance of recovering from mistakes because it has a lower deposition rate. That's why professional groups like I-CAR, the Inter-industry Conference on Auto Repair, recommend using .023 in. diameter wire for most collision repair work. For welding material 18 ga. and thicker, you may be able to use a .030 in. wire for higher deposition rates.

    For welding mild steel, choose an AWS E70 wire in S-2, S-3 or S-6 classification. For shielding a shielding gas, always use a high argon-based gas, such as 75 percent argon/25 percent CO2 gas (commonly called 75/25 or C25). Argon carries less heat than pure CO2, and you'll get less spatter.

    The two most popular wires for aluminum are ER4043 and ER5356. While the latter feeds more easily, choose ER4043 in .030 in. diameter to solve heat-related problems. ER4043 melts at a lower temperature and uses slower wire feed speed, often making it the superior choice in sheet metal applications. Always use 100 percent argon shielding gas.

    For welding 304 stainless steel, ER308, ER308L and ER308LSI wires are compatible. For welding 316L stainless, you need a 316L wire. Use a "tri-mix" shielding gas consisting of 90 percent helium/8 percent argon/2 percent CO2. Note: Do not attempt to weld thin metal with flux cored wires. These wires use more heat because they require globular transfer. Unlike short arc, where the weld puddle cools every time the wire touches the base metal, the arc remains "on" constantly with globular transfer.

    Electrode Polarity
    For welding with solid wires, use electrode positive or "reverse" polarity. While EP directs more heat into the base metal than electrode negative (EN or "straight" polarity), you will obtain the best results with EP and following the guidelines provided here. If you've been using flux cored wire, be sure to change your machine's polarity from EN to EP.

    GTAW Electrode Selection & Preparation
    Forget the ubiquitous 1/8-in. diameter tungsten electrode and use a smaller one. They come in diameters down to .020 in. Smaller electrodes carry less heat and enable you to better focus the arc in a smaller area. For steel and stainless steel applications, keep the tungsten pointed, and be sure to grind parallel with the length.

    For best results on thin aluminum, use an inverter-based power source (see GTAW power source recommendations) and forget another popular practice: welding with a pure tungsten and balling the end. Instead, select a 3/32-in. diameter tungsten with 2 percent cerium (2 percent thorium as a second choice), grind it to a point and put a small land on the end. Compared to the balled tungsten used with conventional GTAW machines, a pointed electrode provides greater arc control and enables you to direct the arc precisely at the joint, minimizing distortion.

    Aluminum Preparation
    Clean all metals before welding, but especially aluminum. Remove oil and dirt with a degreaser/solvent. Just prior to welding, remove oxide with a stainless steel wire brush, grinder or chemical oxide cleaner. When exposed to air, an oxide layer forms on aluminum - and aluminum oxide melts at a temperature 2,000 degrees Fahrenheit higher than plain aluminum! Any slacking in weld preparation degrades weld quality and integrity, so be diligent.

    If you store aluminum in cold places (outside, unheated warehouses), bring it up to room temperature and eliminate condensation. Do not heat cold metal with an oxy-fuel torch (which is a common practice, but not a good idea). This can drive carbon into the oxide coating.

    Universal Advice

    Weld Technique
    Direct the arc at the middle of the weld puddle. Normally, you would keep the arc on the leading edge, where the weld puddle is thinnest, to drive the arc into the work for more penetration. However, staying back enables the puddle to insulate the base metal from the arc's full force.

    To prevent burn-through and warping, do not whip or weave the torch, as the more time you keep the arc in an area, the hotter it becomes. Always travel in a straight line and use the fastest travel speed possible that maintains a good bead profile.

    Skip Welding
    Unevenly distributed heat causes distortion and warping, which in turn wreaks havoc on parts that theoretically fit together. To minimize warping, distribute the heat as evenly as possible. You can accomplish this by using a skip welding technique.

    For example, let's weld a 2 x 2 ft. piece of 18 ga. stainless steel to repair the side of a tank. Start by making a 1-in. long weld. Skip 6 in. and make another 1-in. long weld. Continue to work your way around the plate's circumference, welding 1 in. out of every 6 in. You may have heard of this as a 1" on 6" weld. After you've traveled around once, make your next 1-in. long weld 3 in. from the first weld. Continue to place the second set of welds between the ones you made on the first pass, and so on until you achieve the integrity desired.

    The same technique holds true for welding linear parts. If the metal starts to warp or pull to one side, solve this by: increasing the distance skipped between welds; welding at the beginning, middle and end of the piece, then repeating the sequence; or welding on alternate sides of the joint.

    Backing Bars
    To dissipate heat from the weld area faster than atmospheric cooling alone, place the heat affected zone (HAZ) in contact with a "backing bar" or "chill bar." A backing bar can be as simple as a metal bar (usually copper or aluminum because they dissipate heat best) clamped to back of the weldment. This simple technique enabled one fabricator to use an all-in-one pulsed MIG power source to weld a continuous seam on .040 in. aluminum.

    In higher-duty cycle applications, you may need to consider a water-cooled backing bar. Elaborate versions feature a water cooler that circulates chilled water or special coolant through holes drilled in the bar. Simple, homemade versions feature a water cooler circulating coolant through PVC pipe touching the back of the bar.

    Fit-up and Joint Design
    Welding thin metal demands tight fit-up. Imagine a butt weld on 20 ga. metal. If the parts fail to touch for even 1/16 in., you have just created a hole that begs for burn-through and left a gap that cannot absorb the heat. On thicker metal, the edges of the metal can support the arc, but not here. Gaps cause nothing but trouble. To avoid rework caused by burn-through, adhere to the old saying "measure twice, cut once."

    If you can redesign the part with joints that can withstand more heat, do so. For example, instead of a butt weld, can you make a lap joint? If you can, you double the amount of metal available to absorb heat.

    Don't Overweld
    Most people, especially those without formal training, feel compelled to overweld a joint to obtain greater strength. Assuming you have sufficient heat, the leg of the joint (the long side of the triangle) does not need to be any longer than the thinnest plate. For example, when welding a 1/16-in. plate to a 1/8-in. plate in a T or lap joint, the weld only needs to be 1/16-in wide. Excessively wide welds reduce travel speed, waste time, waste filler metal and gas, may lead to unnecessary post-weld grinding, and may affect the temper of the metal.

    GMAW Power Sources

    When selecting a power source for short circuit GMAW, use one with good voltage control at the low end for good arc starts and arc stability.

    If you plan to buy an all-in-one power source that uses 115V household current, go with one from a major manufacturer of industrial welding equipment. Machines with low-ball prices simply do not have the slope and inductance necessary for good control over the short circuit. Be sure the unit comes with a contactor and gas solenoid valve; some units designed only for flux cored welding do not.

    If you plan to weld with an all-in-one power source in the 200 to 250 amp range, look for one with a spool gun that connects directly to the front panel. This eliminates a lot of hook-up headaches by letting you switch instantly between two different wires, such as .023 hard wire in the "regular" gun and .030 aluminum wire in the spool gun. To weld aluminum down to .040 in., Miller's Millermatic® Pulser provides the best value for moderate-volume fabricators because it features built-in pulsing capabilities.

    For high volume work, both 200 to 300 amp all-in-one units and industrial, production type machines can weld sheet without exceeding their duty cycle. While several all-in-one units provide excellent results, they cannot compete with industrial machines for controlling spatter. If you currently spend a lot of time on post-weld cleaning and grinding spatter, you may be able to increase productivity and lower overhead costs by upgrading your power source technology. Remember that gas, wire and the power source account for less than 15 percent of a weld's total cost; 85 percent comes from labor. Far too many companies try to save pennies by cutting welding costs while obliviously wasting dollars on grinding time.

    For metals in the 1/16-in. to 3/32 range, consider investing in a pulsed GMAW system when bead appearance and no spatter are factors. Pulsed GMAW is almost spatter free and provides faster travel speeds than short arc, so it can pay for itself very quickly. Pulsed GMAW may be able to replace GTAW in some applications to improve travel speeds. Again, industrial power sources with built-in pulsing controls, such as Miller's Invisionâ„¢ 354MP, provide the best value.

    GTAW Power Sources

    GTAW power sources come in two basic categories: those with a DC output for ferrous metals and those with an AC/DC output for non-ferrous metals as well. For welding thin steel or stainless steel (and no aluminum), invest in one of the new GTAW inverters that feature pulsing controls and HF arc starts, such as Miller's Maxstar® 200 DX or Maxstar 150 STH. Pulsed GTAW, which allows the weld puddle to cool between pulses, is one of the easiest methods to prevent warping and burn-through.

    For welding thin aluminum, use a GTAW machine with an adjustable squarewave output. By fine tuning its "balance control," or adjusting the EN to EP ratio, you can narrow the weld bead and take heat off the base plate.

    For unbeatable results on thin aluminum, use an inverter with advanced squarewave technology, such as Miller's Dynastyâ„¢ 200 DX. These machines feature extended balance control (up to 90 percent EN, versus 68 percent EN for convention technology) and an adjustable output frequency (typically from 20 to 250 Hz). Inverters create the narrowest arc cone possible and let you weld in the AC mode with a pointed tungsten. You can precisely direct the arc, establish the weld puddle faster and place the filler wire right where you want it. People who weld with these inverters consistently state that they make aluminum weld almost like steel.

    http://www.brighthub.com/diy/automotive ... 7.aspx?p=2
  3. grumpyvette

    grumpyvette Administrator Staff Member

    utomobile metal repair and panel welding
    Posted on June 30, 2010 by Bruce

    I was talking to a nice gentlemen recently who had read my rust article. He wanted to know if the guys who had redone his Camaro did it correctly. I asked him if he had any photos of the resto process. Well in fact he didn’t. But he described what he had seen when he visited the restoration process. I had a few follow up questions that he couldn’t answer, bottom line I can not stress enough how important progress photos of your restoration or car build are. Photos are the only way to document what was done to your car.
    Moving forward I think this guy has some interesting questions about how to properly repair or restore the body on any car.
    Let me start this explanation by saying that I was learning the body trade in the late 50s. This was an interesting time in the evolution of automotive metal work in the new car construction. Going back to the early beginning of car construction on assembly lines The sheet metal used in body panel stampings was much thicker than it is today. Since the late 20’s and early 30’s where it was not uncommon to see sheet metal on cars that was 10 and 12 gauge metal. Most body panels were 14 gauge. Connecting body panels was achieved by fixing the steel panels to a wooden body skeleton with nails and or screws. Accident damage was repaired by hammering out the dent and metal working the area until it could be filed smooth. The addition of Lead applied to the metal provided another way to smooth the panel before painting. Lead soon became an accepted repair method. Experienced leaders also became body artists in customizing metal bodies. When I came on to the car scene in the late 50’s sheet metal was much thinner so the hammer and dolly technique was an art, too much was a bad thing. Wood skeletons were gone. Body panels were welded together and exterior seams were leaded. The practice of attaching panels was being done by the form of “spot welding” Somewhere along in the late 40’s fiberglass car bodies were “experimental” In the early 50’s “Bondo” a plastic body filler was making it’s debut, and has been misused ever since.
    Not to say that new technology hasn’t improved many aspect of automotive body work, but if we take a look at the old school methods we might get an understanding of what works and why. Going on the premise that back in the 50’s a body repair was done to be permanent. Today insurance companies consider an auto body repair permanent if it lasts 3.5 years. Dissimilar materials rarely stick to each other forever. Plastic body filler isn’t permanent, over time it lifts, puckers, shrinks, or peels. When was the last time you saw lead crack chip or peel on an auto repair. Enough said about smoothing body work techniques, remember “less is best.”
    That brings us to the last tidbit of metal body work, or the art of welding and panel fitment or replacement. There should be no argument that the best repair to a metal car body is the exact body panel replacement attached in the exact method done by the factory. Lets say you have a rusted out quarter panel on a 1965 Mustang Coupe. In my opinion the best way to fix the rust is to remove the complete quarter panel, call the factory and order a OEM quarter panel and attached it with spot welds following the factory weld map, the roof seam gets lead and the trunk seams get a touch of sealer. Well you and I know that there are a few flaws in that procedure, primarily it is next to impossible to get OEM panels for older cars. So we are stuck with aftermarket panels that may not be the same gauge or of the same stamping quality of OEM panels. Even when working with complete aftermarket panels they can be still be attached just like the factory did it. Often we find that a lot of shops don’t have the same spot welding equipment as the factory. Consequently, other welding methods are and can be used. Bear in mind that the more heat that is applied to a metal panel the more “oxidation” occurs. Yep heat causes metal to oxidize. Isn’t the rust or “oxidation” the reason we are doing this in the first place? Remember in the welding repair process you will need to assure yourself that where heat was applied to weld the metal, you are able to clean up the metal and treat it so that the oxidation process is stopped or slowed as much as possible.
    What if you have to repair metal and no complete panels are available, what then? Well this is where many opinions enter into the “what’s right, what’s wrong” arena. Many body guys think that butt welding replacement panels in is the only proper way to go. Others still use a “lap” seam to put partial panels on existing sheet metal. First let me say that butt welding eliminates the pocket between two panels that traps moisture and creates rust. But I must say it takes a very skillful welder to butt weld a big patch panel into existing sheet metal without causing a lot of distortion. The more distortion, the more body filler is needed, now you have a whole different set of problems. Remember when it comes to any filler “less is best” As an alternative is the overlay of panels, as we discussed this method put two pieces one on top of the other using a 1/2 inch lap seam. The lap seam gives moisture a place to start oxidation. If you can seal both sides of the seams you will slow the possibility of oxidation occurring. Don’t forget that the factory uses a type of “lap joint” when they spot weld panels together. When performing a lap weld on an external panels I will always sweat the seam with lead when the welding is complete. Lead goes a long way to “seal” the lap joint. Bottom line either method can work well, both methods have pluses and minuses, sometimes you just have to trust the advice of the guy doing your work. Document it with photos.
    Well we have looked at spot welds and the types of welds but we haven’t discussed the type of welding equipment. Whether it is electric stick or wire feed, Mig or Tig, or gas and stick, good results can be had by any experienced welder with any choice of welding process. One thing to be mindful of in the “good old days” we worked on body panels with the “less heat” approach. Braze was one such method that used less heat than arc or gas welding. When we were finished brazing a panel it was most always smoothed with lead before painting. I don’t ever remember problems when doing this type of repair. In recent work we notice that the plastic fillers have a tendency to “lift” or separate from braze material over time. This mystery of separation, seems to be due to the flux residue in the brazing process. So don’t use plastic filler over a brazed seam or joint. If you lead the braze first then apply the plastic filler I don’t think you will have a problem with “lifting”
  4. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  5. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    I've had several people ask me how difficult it would be to,
    replace the floor pan in a muscle car project they recently purchased,
    obviously the extent of the damage and the availability of aftermarket or O.E.M, body panels,
    will be a factor , but you can rather often find youll need to fabricate floor pan panels.
    as usual , youll find accurate measurement is important, and you may want too use a few pop rivets or cleco pins to hold the replacement panel in place during the floor panel replacement.
    this is a job the typical 110 volt MIG welder is easily up to completing.
    be very area welding around any flammable object like seats, wiring and the fuel lines or gas tank, is not a good idea, so keep a fire extinguisher and a running garden hose in close proximity to the area your welding and its always far smarter to bring the car out of your garage to weld in-case the car does catch fire.

    a small sand blasting gun used to clean the metal surfaces to be welded ,and a tool that is used to accurately cut the floor boards like a plazma cutter or NIPPER is a good idea.







    Last edited: Feb 18, 2019
  6. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  7. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    visit your local major book store and look in the auto related section,
    youll find at least a few books on welding that will help a good deal.
    for sheet metal, youll want a few specific tools and a decent mig welder , but for most repairs even the reasonably cheap 110 volt migs with the proper shield gas and wire will function reasonably well.
    be aware its the,
    surface prep. and careful cleaning,
    shield gas , used,
    amp settings,
    and wire diam.
    that all have a very profound effect on the weld quality
    and of course your skill and experience and ability to weld

    Ive used this lincoln MIG in the past with decent results

    this eastwood is owned by a friend who likes it alot

    I like my miller 252 mig , but its certainly over kill for sheet metal repairs












    Last edited: Jan 24, 2021
  8. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    Ive had several friends purchase welders from HF,
    the results vary considerably , and it should be obvious that a decent MIG welder even a rather cheaper versions will work fairly well,
    as with most things you tend to GET WHAT YOU PAY FOR,
    IN my experience and listening to most of my friends,
    anything much under about $400-$500 is not going to be high quality and good for decades of trouble free use with only minor maintenance,

    but theres a huge difference between a cheap FLUX CORE welder ,
    and a decent lower cost MIG welder...
    hobart, lincoln, eastwood and other vendors also sell lower cost MIG welders , youll want to decide on if youll be reasonably well served with a 110 volt 140 amp mig or need something with more capacity,
    understand DUTY CYCLE, if a welder says 30% duty cycle at x amps its means you weld for 3 minutes and let cool for 7 minutes
    before it can be used again,
    lower amps generally allow higher duty cycle,
    most people find low duty cycles very BIG P.I.T.A.
    anything that almost any welder advertises, that says FLUX CORE is not going too be high quality mig.
    while not always true ,because designs and components differ higher WEIGHT is also an indicator of better quality
    why not visit a local lincoln dealer and ask questions
    the eastwood welders have a decent reputation










    https://www.harborfreight.com/search?q=mig welder



    Last edited: Jun 10, 2019
  9. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    a couple hours reading linked info could easily save you hundreds of dollars and days of problem solving,
    Id point out that decent quality, 110 volt 120 amp mig will do a decent job on sheet metal,
    but most are limited to work on under 3/16" thick metal and thats really pushing the limits,
    now that may be on a 20-30% duty cycle, that requires you to weld 2-3 minutes and let the welder cool 7-8 minutes between welds
    if you spent a bit more you get a 220 volt 180 amp-210 amp welder , if used at the amps required for sheet metal , duty cycle is far higher
    maybe at 70% so you weld for 6-7 minutes and let cool for 3-4 minutes.
    you rarely weld for more than a minute or two, so in reality, you can use the 180-210 amp rated migs almost constantly
    if used on the lower amp settings
    go a bit excessive, get a 230-250 amp mig and your duty cycles high enough that you ignore duty cycle limitations

    yes Im a tool junky
    I don,t know how anyone in this hobby can get by without a decent welder.

    this miller 252 migs been damn useful, and its most likely the most practical choice,but I've found I use both a MIG and TIG and occasionally an ARC welder.
    if limited to a single welder I think it would be a 250-300 amp range TIG with a water cooled torch, and easy switch adjustable polarity, adjustable frequency, and amps (yes the foot petal works on my tig

    Duty cycle is a welding equipment specification which defines the number of minutes, within a 10 minute period, during which a given welder can safely produce a particular welding current. For example, a 150 amp.welder with a 30% duty cycle must be "rested" for at least 7 minutes after 3 minutes of continuous welding.









    Last edited: Jun 10, 2019
  10. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    Last edited: Aug 22, 2020
  11. Roger Jam

    Roger Jam New Member

    MIG (Metal Inert Gas) Welding (also called GMAW or Gas Metal Arc Welding) joins metals by heating them with an arc between a continuously fed cable (filler metal electrode) and the workpiece. Externally supplied gas or gas mixtures provide shielding(available through the Thoroughbred Industrial Cylinder Exchange).

    The type of shielding gas depends on the sort of wire. For mild steel wire, the gasoline is C25 (that is, 75% Argon and 25% CO2) or CO2. For aluminum wire, the gas is Argon. For stainless steel cable, the gasoline is called"tri-mix" (a mix of Argon, CO2 and helium).

    The advantages of MIG welding include:

    • Welds steel, stainless steel, and aluminum
    • Continuous wirefeed makes it the simplest method to learn
    • Produces cleaner welds compared to other procedures
    • May Be Used for high-speed welding
    • Provides good control on thinner metals
    • Great for out-of-position welding

    The disadvantages of MIG welding include:

    Mustn't be used in blustery conditions
    All rust and paint needs to be cleaned off the substance before welding

    Wire-feed welders like flux-cored and MIG welders, act like a caulking gun. If you pull the trigger on the gun, then the cable feeds out continuously until you release the trigger or operate out of cable.

    The Benefits of flux-cored welding comprise:

    • Continuous wirefeed makes it the easiest method to learn
    • Welds steel and stainless steel
    • Works well on dirty, paint, and rusty material
    • Good for out-of-position welding
    • Can be Utilized in windy conditions
    • has increased metal deposition rate
    • Provides deep penetration for welding thick sections
    The disadvantages of flux-cored welding comprise:

    • Demands slag removal after welding
    • Produces a lot of spatter that needs clean up following welding

    (The tungsten electrode( unlike a pole electrode, doesn't become a part of the finished weld). Filler metal is occasionally utilized and Argon inert gas or inert gas mixtures are used for protection.

    The Benefits of TIG welding comprise:

    • AC TIG welds aluminum and magnesium alloys
    • DC TIG welds aluminum, brass, steel, stainless steel, and ceramic
    • Provides the Maximum quality and most exact welds
    • Capability to weld thin stuff

    The pitfalls of TIG welding comprise:

    • Requires more skill and expertise than any other method

    Resistance spot welding (also known as merely spot welding) combines two pieces of metal by passing current between electrodes placed on different faces of the bits to be welded. There's not any arc with this procedure and it's the resistance of the alloy into the present flow which leads to the fusion.
    The Benefits of spot welding comprise:

    • Welds steel and stainless steel
    • Comparatively Simple to Use
    • No shielding gas required

    The disadvantages of welding include:

    • Mainly used for sheet metal work

    First, I always try to use the best welding machine for the work. I'd also recommend that if you're really into welding and want to work on this in the long run, go for the most premium machines in the market. I'm more of a MIG welding and have Hobart, Forney, and Lincoln Electric machines for the work. We're basically a group of friends working on DIY projects - creating quality antique pieces with welding.

    MIG welders are great for beginners and you can't imagine what an expert can do with these. They're easy to use and offers more control on the welding surface. Also, I'd recommend selecting a flux core and one mig welder.

    This video might help getting you started.

    <iframe width="560" height="315" src="" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

    Also, to choose the best welder for yourself, you can choose any one of these. https://weldingrage.com/best-mig-welders/

    Last edited by a moderator: Apr 10, 2021 at 3:58 PM

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