There are dozens of books on the market that describe the welding process. Beyond that resource, there are tutorials and welding instructions freely available online. There’s no need to repeat all that information in this book.
Instead, this chapter offers a brief background in commonly used welding supplies and basic settings for common welders. Then we move on to some tips for producing good, strong welds and a few techniques to practice before you commit a weld to your project.
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Getting the right supplies for your project is critical. You may have seen MacGyver on TV making a weld with a pair of jumper cables and a quarter, but that’s really not a recommended technique. The good news is that you’re not likely to need everything you can find in a welding shop. A good used MIG welder and a few basic general-purpose selections of wire and gas will get you through almost all projects.
The most important factor in choosing any welding rod (or filler) is to choose a rod made from the same material you are welding. There are different rods and wires for mild steel, stainless, aluminum, and so on. Next, choose the diameter of your rod or wire based on the thickness of the metal you plan to weld and the power level you need to use. For most purposes, the smaller range of rods and wires is what you want. Finally, set your welder up with the correct amperage, gas flow, and so on.
We could fill a book with tables of settings to cover all these variables, but the welding supply companies have already solved that problem. When you buy welding rod or wire, ask for the Material Safety Data Sheet. The MSDS, as it is commonly known, contains information about the composition of the welding rod and its flux (if any). It also generally contains a table listing common welder settings and recommended applications for the rod.
MIG and Wire-Feed Supplies
If you plan to use a wire-feed welder on steel, you have two basic choices for welding wire: flux-core and solid metal. Flux-core wire includes its own welding flux—a material that burns and creates the air-free area in the vicinity of the weld. The flux also forms a crust over the surface of the weld that you must chip or brush off as the weld cools. If you try to weld over the crust, some of it will become trapped as a bubble in the weld, which reduces weld strength and looks ugly.
The benefit of flux-core wire is that you don’t have to deal with a bottle of gas. You just plug in your welder and start working. The downside is that flux-core wire requires AC operation and produces a lot of smoke and splatter. Flux-core is also not recommended for welding thin (20 gauge or less) materials. With a small bottle of MIG gas (generally a mixture of argon and carbon dioxide) you can work using DC and get a much smoother weld. Common flux-core wire choices for automotive work include Lincoln NR-211 or any wire that meets the AWS (American Welding Society) E71T-GS standard.
For best results in MIG welding, you need the right kind of gas to keep oxygen and nitrogen (98 percent of ordinary air) away from your weld. There’s a price range between different welding gases, and of course the better formulations are more expensive. You can use pure carbon dioxide (CO2) and it works, but you get better results by purchasing a gas with 75 percent or higher argon content. For aluminum or other non-ferrous welding, you want 100 percent argon or helium, but these pure gases are not suitable for welding mild steel. To weld stainless steel, a small amount of hydrogen or another reactive gas is added to a basic argon/carbon dioxide mixture. You can also purchase three-way welding gases that include some combination of helium, argon, carbon dioxide, and a small amount of oxygen.
For the vast majority of automotive mild steel welding, an 85 percent argon and 15 percent carbon dioxide gas mixture is a good choice. Your welding shop can make a recommendation about alternate mixtures for specific purposes.
Most mild-steel MIG welding wire is made to the ER70S AWS specification. There are subdivisions— ER70S-3 and ER70S-6 are the most commonly used mild steel MIG welding wires, and the -6 variation is generally considered easier to use. These specifications include elements in the alloy that allow the wire to flow well and create a good, solid weld.
If you plan to weld aluminum, you absolutely need a bottle of argon or helium gas. Aluminum oxidizes easily and the protective gas is a requirement. You also need aluminum wire and special rollers to push it. The most popular aluminum wire selections are a solid core 4043 or 5356 alloy. The 4043 wire is the most popular and easy to work with. The 5356 alloy is harder, and should be used when you plan to anodize (color) your work, because 4043 weld material does not take the color well. If you will be welding aluminum regularly, you also should invest in a spool gun. Because 4043 aluminum wire is soft, mounting the wire spool right on the gun allows a shorter wire travel, which is easier on the wire and reduces breakage and wire jams.
If you plan to weld stainless steel, you need stainless steel wire. The most popular alloys for stainless welding are 304, 308, and 316, and you need a special gas formulation as well. Gas for stainless welding includes a small amount of hydrogen or oxygen.
TIG Welding Supplies
TIG welding rods are similar to those used in oxy-acetylene welding in that they come in lengths of straight rod in different sizes from 1/16 to 1/8 inch. Like MIG welding wire, TIG rods are available in a variety of alloys based on the material to be welded. There are two main rod formulations for mild steel, known as S6, 70S, and 80S- D2. Steel welding rods have a thin layer of copper plating on their surface to resist rust and promote puddling. Aluminum formulations are not plated and come in 4043 and 5356 alloys, just like MIG wire. Similarly, stainless welding rods are available in 308 and 316 alloys. Most TIG welding is performed using 100 percent argon gas, but mixed gases also work well.
With a TIG welder, you also need to stock a supply of the tungsten points for your welding gun. These points are made primarily of tungsten, but the trace elements included in the manufacturing process distinguish several kinds of points. The most common points used are 98 percent tungsten with 2 percent of thorium added. This kind of point has a red tip, and it’s a good generalpurpose point. You may also want to buy a selection of different tips for various purposes.
TIG tip maintenance is easy. You can create a ball of tungsten at the end of the point by simply making an arc—the ball will develop on its own. For fine work, keep the point sharp with a whetstone or TIG point grinding machine. For highpower work, grind the tip flat for a larger arc point.
There are a tremendous number of choices in oxy-acetylene welding rod. For mild steel, most choose the copper-coated RG45, RG60, and RG65 rods. Each of these has a slightly different formulation, but all work well in an automotive steel context. You can also get a variety of specialty rods made of bronze (for brazing), aluminum, stainless steel and other materials. Many of these rods are flux-cored or fluxcoated for brazing.
Gas options center mainly around the combustible fuel. Acetylene is the most common gas used, followed by propane. You can also obtain hydrogen, proprietary MAPP gas, natural gas, or liquid petroleum gas for your torch. In general, acetylene is the fuel of choice. Welding oxygen has been dried to prevent the tanks from rusting. You should never use medical oxygen or other oxygen sources for welding—get your oxygen from a reputable welding shop.
Be sure you always use, transport, and store your welding bottles in an upright position. Acetylene is dissolved in acetone when it’s placed in the bottle, and if you put the bottle on its side, the acetone can get into the valve and then into your regulators. If your bottles have been on their sides, stand them up and let them stabilize for an hour or so before you attach your regulators and try to use them.
Stick Welding Supplies
There are a wide variety of stick welding rods available on the market, each optimized for a different kind of welding. Because a stick welder has only a power adjustment, we use different rods to meet various different welding requirements. For example, if you’re welding something very easy to work with such as clean new metal, well-fit with no gaps, choose 6013 rod. This formulation is easy to work with, easy to clean, and generally gives good results when everything is in order. If you’ve got gaps to fill, 6012 is a better choice.
The numbering system on stick welding rods is fairly simple. The first two digits (60 or 70) indicate the tensile strength of the weld at 60,000 or 70,000 psi. The third digit indicates the welding positions approved for the rod generally 1 for all positions or 2 for flat/horizontal only. The last position describes the electrical current requirements and the composition of the flux coating. Generally speaking, 1 and 5 indicate DC-only, and all other digits indicate AC/DC operation.
When choosing a rod to use, start with the composition of the material you plan to weld. If you’re working with mild steel, the basic rods listed here are good choices. If you’re welding stainless, joining unlike materials, or working with other alloys, you should consult your welding shop for a recommendation. Gauge your rod diameter by the thickness of the material you’re welding and the amperage you’re using. In general, choose smaller rods for lower power settings on your welder. For a rule of thumb, 3/32-inch rods are good to about 75 amps, 1/8-inch rods from 75 to 150, 5/32-inch rods from 100 to 175, and 3/16-inch rods from 150 to 250 amps or above.
Stick Welding Positions: One of the characteristics listed for each kind of stick welding rod is the position in which it is best used. Stick welding makes a distinction between flat (as if the piece is lying on a table and you are standing above and next to it), vertical, and overhead welding. Most modern rods are good in any position, but a few are recommended for use only in the flat or horizontal position.
The table on this page shows the kind of welding indicated for each type of standard rod. The table on page 40 lists the current and polarity settings for the most commonly used stick welding rods.
Taking Care of Stick Welding Rods: Stick welding rods must be absolutely dry for best results. Rods that have been wet can be identified by their disintegrating flux coating. Like the head of a wooden match that has been dipped in water, the flux dissolves and comes apart easily.
You can buy an oven to store and pre-heat your stick welding rods, or make a simple hot box. A hot box is just an old metal cooler or refrigerator insulated and sealed with a light bulb inside to keep the inside warm and dry. The most common solution is simply to purchase a watertight plastic rod case. These are plastic cylinders with gasketed screwtop lids. Put your rods in one of these cases and remove only as many rods as you need. Otherwise, keep the case sealed.
Preparing to Weld
To create a strong and good-looking weld, you need to have good technique, but it’s just as important to prepare your project. The best welder in the world can’t get good results if the piece isn’t cut, cleaned, and supported properly. Similarly, if the welding machine is not correctly adjusted, it’s hard to get good results. Use the sections below to ensure that your weld is set up to succeed before you start.
Getting Good Fit-Up
Good fit-up of the pieces to be welded is the basis for a good result. When you measure and cut your parts, measure carefully and allow for the width of a flame or blade when you make your cuts.
With small parts and tubing, you want to get them right up together for the best results. For thicker materials, you generally bevel the mating edges to give your weld bead a place to go.
Getting the measurements and markings correct is especially important when you’re cutting angles. Using a jig, miter box, or locked setting on a chop or band saw is important because a tiny angle error at the weld end is multiplied through the length of a piece and the other end of the bar may end up wildly out of alignment.
As a rule, if you have to estimate a cut, estimate it too long. You can always cut more off a piece of metal, while adding length is very difficult. When cutting a straight angle, estimating a little long allows you to cut or grind the angle again if it’s not just right.
Getting angles exactly right is especially important with tube projects, as you may be fitting a fishmouth end around round tube for a weld. Even with a tubing cutter, it takes some practice to get these fitments exactly right.
Cleanliness is critical to a good welding result. Mill scale, oil, grease, dirt, paint, metal filings and other contaminants get into your weld and show up as bubbles, slag, clinker, and porosity. It’s ugly and it reduces the strength of your weld. Start cleaning your work with a good wire-brushing. Grinding and sanding also works to remove paint and adhesives, but can leave its own impurities behind. Brush and grind your work until the metal shines, but don’t remove too much of the material. You want plenty of metal to make the weld.
If the metal you’re working has previously been coated in paint, oil, grease, cosmolene, or any kind of protectant, you may want to wash it with a cleaning solvent. There are several commercially available cleaning solutions available at your welding shop, such as Ox-Out and Chemclean. These are acidic cleansers that remove oil, grease, mill scale, rust, and other impurities from your working surfaces.
Supporting Your Work
When your metal is fitted properly and cleaned of all scale and impurities, you’re ready to position the parts. It’s important to get the parts positioned correctly and securely before you start welding. This is when it’s handy to have a welding table to prepare your parts. If your parts are long, you may need additional stands to support them at either end and at one or more places in the middle. You can buy or make variable-height welding stands (sometimes called a dead man) using threaded rod and a tripod stand. You can also use sawhorses, tables, stacks of boxes, or anything else that is available. The important thing is that your parts must be held firmly in the proper orientation. Parts sometimes move when you start to weld, and cutting your pieces apart to try again is extremely tedious.
Don’t be afraid to tack-weld your parts to your welding table. If you have a selection of carpenter’s squares, protractors, or magnetic angles, measure in every possible way to make sure that your right angles are square and that everything fits and lines up the way you planned.
If you plan to make multiple copies of a structure, you may find it useful to create a jig. A jig is simply a setup that allows you to make several parts exactly the same way. For example, you might tack-weld some pieces of angle or box stock to your table such that your pieces fit precisely where you want them. If you cut the parts to the same length and use the same jig, you should be able to come up with identical parts every time.
You can make a temporary jig out of scrap pieces of steel to hold parts. Simply cut your scraps to the correct length, tack them onto your table and then tack your part to the supporting piece. When you’re all done, break or cut the support loose and grind the tack weld down.
Take the time to observe your parts from every angle and make sure that the fit is correct and everything is aligned properly. Reworking a welded piece is never easy, and you can easily ruin a part (or several) and have to start over. Spending the time now to ensure that everything is right will pay off shortly.
Preparing Your Environment
It’s more difficult to weld in full daylight because the light from the sun gets into your mask and limits your ability to see the weld. Also, you can’t see the glowing metal as readily in the full light of day. It’s best to weld indoors if you can do so safely, or at least in a shaded area where you can see what you’re doing through your mask.
Wind is also your enemy when you’re welding. Wind blows away the shielding gases from a MIG or TIG welder, and even from flux-core wire or the flux on a stick welding rod. On the other hand, your welding environment should be wellventilated to replace the smoke and fumes from welding with fresh air for you to breathe. Once again, indoor welding is best, provided you aren’t creating a fire or ventilation hazard.
Get your safety gear together. It’s often tempting to just make a tack or run a short bead without your protective gear, but that’s precisely when you’ll get burned. Keep your safety gear with your welder and it is always close at hand when you’re ready to weld. Make sure you’ve selected the appropriate grade of lens before you begin to weld.
If your helmet is autodarkening, make sure its settings are appropriate for the type of welding you’re about to perform.
Every welding machine is a little different, so getting your welder adjusted correctly is an art. But follow these steps and you should get into the ballpark. Then run some test beads on scrap steel of the same form and thickness as your parts and you can dial in the exact settings you need.
AC, DC and Polarity
Electrical current comes in a variety of forms—120, 240, or 480 volts, it can be single phase or three phase, and it can be delivered as alternating or direct current. In basic terms, alternating current (AC) means that the direction of electrical flow changes about 60 times a second. Direct current (DC) means that the flow of electricity is constant in one direction.
Virtually all wall sockets deliver alternating current. Many welders pass the alternating current through to the weld. However, you may be able to select AC or DC with your welder. A DC setting on the welder converts the incoming electricity to direct current before using it to weld.
Different base materials, welding wire or rods, and welding techniques are suited to AC or DC welding. One is not better or worse than the other. You just have to know when to use each setting with different metals and welders.
In addition to current selection, many welders allow you to select polarity when welding with direct current. DC straight polarity is when the clamp is positive and the welding rod is negative. Reverse polarity has the clamp as the negative side of the circuit and the welding rod as the positive. Polarity is important with some stick welding rods.
Wire-Feed and MIG Settings
For a wire-feed welder, select a power level appropriate to the thickness of your working material. Your welder may have switches or a dial to control the power, but the adjustment process is the same. Start at a lower power than you think you need and run a few test beads. Check for adequate penetration by turning the piece over, and when you can see discoloration from the weld on the back side of the metal, you’re working most of the way through the metal.
Wire speed follows the amount of power you select. If your welder uses a pair of switches to control the welding power, you have 4 power settings to choose from. In general, the more power you use, the faster your wire speed should be.
Set your welder to its lowest power setting and set your wire speed at about 30 percent of its capacity and try a few practice welds. Adjust your wire speed until you get a smooth flow into your weld. If the wire speed is too fast, you will find the wire pushing your welding gun back, or breaking off and leaving short lengths of wire sticking out of the weld. If your wire speed is too slow, the arc will skip and sputter and the weld will be uneven. Adjust the wire speed until you get a good smooth arc and weld bead.
At higher powers, you must increase wire speed somewhat. This introduces more weld metal to your bead and with thin materials, you risk burn-through. See the practice exercises below for more information on setting up your welder. With the speed set, adjust your wire drive force, or tension. This is achieved at the roller wheels that push the wire through the cable to your welding gun. The rollers must be tight enough to push the wire as it is consumed at the arc point, but not too tight. Set the tension starting from the minimum, so the that wire barely feeds. Then hold the welding gun near a flat, unweldable surface such as concrete. The roller wheels should slip rather than push the wire.
Then gently increase pressure until the rollers begin to push the wire out against the test surface. You need only a small amount of force behind the wire. For a MIG wire-feed welder, you also need to adjust the gas flow. There’s no harm in using too much gas—it’s just expensive—but you must ensure that there is adequate gas flow to your welding gun. Twenty pounds at the regulator should be plenty for normal (still air) welding conditions, but you need to raise that if you’re welding in breezy or windy conditions. The table above offers a set of baseline settings for a wire feed MIG welder. These settings are simply a place to start your tests, and they are conservative. For full penetration, higher power settings are almost always used.
With an oxy-acetylene welder, you need to take your welding tip into account. Different welding tips have different aperture sizes to yield a larger or smaller flame. Close the valves on your torch and set your acetylene regulator to about 7 pounds yield to the torch, and your oxygen to about 20 pounds. Then open the acetylene (red hose, typically) valve and light your torch. You should get a smoky flame. Then slowly open the oxygen valve (green hose, typically) on your torch and adjust the flow until you get a small pencil-point-sized flare of blue-white flame. If you open the oxygen too far or too fast, your torch can snap out and lose its flame. If that happens, close the oxygen valve and start over.
Stick Welder Settings
On a basic AC stick welder, the only setting you control is the power. Start low and work your way up until your test welds show good penetration and no burn-through. Be sure you’ve also selected the right kind of welding rod for the job!
TIG Welder Settings
On a TIG welder, you can control the power at the box, or through the use of a foot pedal. The foot pedal is a wonderful tool that allows you to control the amount of energy going to the arc from moment to moment, and this is part of the reason TIG can be used for very fine work such as welding sheetmetal. You can also control the gas flow to the welding gun and as with MIG welding, you need to ensure that there is enough gas to protect the weld.
Another adjustment you make to a TIG welder has to do with the tungsten electrode. The electrode is pointed, like a needle. This allows the TIG welder to create a very small, precise arc. If molten welding rod or other material accumulates on the electrode, the welder’s efficiency and accuracy are reduced. Similarly, the tip of the electrode is consumed and blunted over time, so TIG users keep a whetstone close at hand to clean and sharpen the electrode. You can also replace a worn electrode in the gun. Most TIG electrodes are double-ended to get the most use out of the material.
Most TIG welding is done with DC straight through (positive) polarity, except when welding aluminum, which is always performed using AC power.
Basic Beads and Joints
When welders talk about beads and different styles of joint, these are the terms heard most often. The differences between joints can be subtle, and all good welds share most of the same characteristics— good penetration, clean deposition, and even beads. Generally speaking, a bead is the deposition of molten metal at a joint between two or more pieces being welded. The joint is where the pieces come together, and the type of joint indicates how the pieces come together. All of the joints listed here benefit from tacking the pieces into place before you try to run a bead.
As you weld, try to balance the amount of heat you put into each of the pieces you’re welding together. For example, if you’re welding a T-joint, the heat from the weld has more area to penetrate in the bisected piece than in the center piece. Therefore, spend more time with the arc on the bisected piece to keep the heat distribution even.
A fillet bead is used on a 90-degree joint, on overlapping plates, or on either side of a T-joint. If you cut open a fillet bead, the shape of the weld is roughly triangular. This is a strong bead for connecting structural pieces, and requires good deep penetration. Usually, this bead does not require beveling the edges of the materials being welded. Keep most of your arc directed at the horizontal piece when making a fillet—you’re just melting a bit of the vertical piece and letting it flow down into the horizontal part. If you put too much heat on the vertical piece you’ll create undercut, which actually leaves the vertical piece thinner than when you started just above the weld bead.
Tacking a T-joint fillet weld on both sides is important because as the first weld bead cools, the thermal contraction can pull the two pieces out of perpendicular alignment. Stitch welding the fillet and alternating stitches on either side of a T-joint also helps prevent misalignment.
Beveled or Groove Bead
A beveled weld is simply a butt weld where you’ve ground a slight bevel onto each mating surface of your parts, making a V shape into which you deposit a fillet weld bead. This is generally easier than making a good butt weld and offers generally good results. With thicker materials, beveling becomes even more important to ensure complete penetration of the weld. Depending on the size of the materials, you may need to run several beads to fill a bevel. There are variations on this theme—the U-groove, J-groove, and single-side bevel are examples, but they all mean the same thing: leave some space for your weld bead to flow into.
Inside Angle or Inside Corner Joint
This bead takes place on the inside angle of two pieces of steel. But for an inside angle weld, only the edges of the two pieces are touching. You have to be careful to lay your weld equally on both pieces if they’re the same thickness, or correspondingly biased if you’re welding a thick to a thin piece. These welds often benefit from multiple passes if the materials are thin and you’re worried about burn-through. Make your first pass a light bead and then follow it up with two more beads on top of the first and biased to each piece, so each subsequent bead attaches both to the piece and to the previous beads. Weave the later beads in a wider arc than your initial bead to get good coverage.
Outside Angle or Open Corner Joint
This is the opposite of an inside angle bead in that it happens at the outside of a 90-degree joint. Most often, the two pieces are placed with only edges touching, creating a natural area for your weld to fill. Make sure you get even penetration into both parts when creating this weld, and you might want to follow it up with a weld on the inside angle.
A butt joint is any time you have two flush edges mated together. There’s little or no room to place a weld bead into the joint, so you have to melt the two pieces together with complete penetration. A good butt weld takes practice, and most welders prefer to give themselves a little bevel to work with. Also, you need to have both pieces securely clamped when welding a butt joint, or heat distortion will pull your pieces out of position. You can butt weld metals up to about 1/16 inch. Thicker pieces should be beveled. If you cannot bevel a thicker piece for any reason, just leave a small gap between the pieces for the welding rod or wire to fill up with bead. If you leave a gap, plan to run a bead on both sides of the butt weld, if possible.
Stitch welding is also known as skip welding or intermittent welding. The technique is useful in controlling the amount of heat distortion you create in a project. By welding a short bead and then skipping a few inches and running another short bead, you can stitch your full weld together while limiting the amount of heat placed into the piece at any given time. After the piece has had a chance to cool, you can return and weld the sections you skipped the first time. A variation on this technique is backstepping, where you start a few inches in from the end of the joint and work backwards to the end, then move farther in and work backwards to the start of your first bead.
A rosette or plug weld is used to fill a small hole, up to about 1/2 inch in diameter. Use a circular motion to deposit filler rod around the perimeter of the hole until it closes up. The name rosette describes the weld because when you do it right, it looks a bit like a flower. This type of weld is also used to join two pieces of tubing where one tube has been inserted in the other. A hole is made in the outer tube and the weld joins the two pieces of metal.
When everything is fitted, clean and ready, and you’ve made some practice beads to warm up, you’re ready to commit welds to your project. Get some scrap pieces of steel for your practice sessions. For these initial practice beads, make sure the pieces you’re welding are the same thickness and the same material. Welding unlike pieces is an advanced project. Run many beads, until you’re confident you can do it right every time. When you’re seeing good results, you can try your technique on an actual project.
Follow these steps to get a good result:
1: Securely mount your ground clamp. With any electric welder, you have a ground clamp to connect your welder to your project. This clamp is half of the circuit from the welder to the material you’re welding. The other half of the circuit is the cable from the welder to the gun or stick holder. You complete the circuit when you strike your welding arc.
Getting a good connection with your ground clamp is important. With steel, you can clamp to the material you’re working or to your welding table, provided you’ve got good contact between the materials and the table. If you’re welding aluminum, you must clamp to the piece you’re working. There are a variety of clamps available, including magnetic clamps. If your piece does not provide a convenient clamping location, you might have to weld a bolt or other extra part to your work to provide a ground.
2: Bevel your edges. You need a place to deposit your weld bead and you want to maximize the surface area for your weld, so it’s a good idea to grind a small bevel onto the edges you’re planning to weld. You don’t have to do this, but it helps make cleaner, stronger welds. Just be sure you leave enough material to hold the weld!
3: Tack your work into place. When you start welding your project together, begin with tack welds to secure everything into place. Your jig and support system is a good start, but by making a whole series of tack welds, you reduce the risk of twisting and warping your work. Welding involves a great deal of heat, and heat expands the metal you’re working. If you weld one entire seam without supporting the other seams in your project, the fitup of your pieces can distort.
Making tack welds with a MIG or wire feed welder is easy. Just hold the gun at the tack point and briefly squeeze the trigger. With TIG or oxyacetylene welders, you need to create a puddle and add a little bit of welding rod to create the tack. Perhaps hardest of all is tack welding with a stick welder, because you must strike the arc and create the tack in the same moment, then simply move the rod away to break the arc. This takes some practice to perform cleanly.
Begin your practice by making several tack welds at every joint you plan to weld. These should be small no larger than the size of a pea and they do not need to completely penetrate the material. Make all of your tack welds before running any kind of a bead.
4: Start with a basic push bead. If you’re using a MIG or wirefeed welder, position the welding gun at one end of the joint you plan to weld, and squeeze the trigger (or step on the pedal) to start the arc and the wire flow. As the arc strikes, look at the puddle of molten metal created by the arc, the material, and the welding wire you’re feeding into the arc. Move the tip of the welding gun in small back-and-forth motions along the welding joint, pushing the puddle along the seam. Keep your motions and your speed of travel even to create a weld bead of uniform thickness. When it cools, your weld should have overlapping edges something like a deck of cards or a stack of pennies spread out along a table.
If you’re using a stick welder, you have to strike your arc with a motion similar to lighting your welding stick like a match. Once the arc is created, hold the stick about 1/8 inch from the material and push the puddle in the same way as with a wire feed welder. You need to move your hand closer to the material over time, as the welding stick is consumed. Don’t touch the material with the stick, or the arc will stop. Similarly, don’t let the gap get too large or your weld quality will suffer and the arc will eventually flame out. When you have used up your rod or finished welding, simply pull the rod away from the material to break the arc.
With most stick welders, the flux covering on the welding rod melts as you work and forms a crust over your weld. Use a welder’s chipping hammer and wire brush to clean off the crust and inspect your work. Never give in to the temptation to weld over the crust even for a little bit. Welding over the crust traps the flux material in the weld, creating a porous, weak, and ugly seam.
If you’re using a TIG welder, make sure your tungsten needle is sharp and that you have the correct kind of welding rod. Position your welding rod and the welding gun at one end of the joint you plan to weld. Step on your pedal to create the arc and observe the puddle of molten metal. Dip the welding rod into the puddle with small motions. Each time you dip, you leave a small amount of the welding rod melted into the puddle. Push the puddle along the seam with small motions, dipping the rod into the puddle to add material to your weld. Getting a good bead this way requires some coordination, but with a little practice, getting a good bead from a TIG welder is not difficult.
With an oxy-acetylene welder, first get your flame set correctly. Since a gas flame operates at a much lower temperature than an electric arc, it takes more time to create a puddle of molten metal. When you have a small puddle, push it with the flame and dip your welding rod in the puddle to add material as you would with a TIG welder. Gas welding generally takes longer and is more finicky than arc welding, but your results can be just as good. Patience is a virtue with all welding, but especially with oxy-acetylene.
5: When you’re comfortable with pushing a bead, you can try pulling a bead. Pulling a weld is a bit more difficult than pushing, but some welders prefer this technique, especially with flux-core wire feed welders.
Using a MIG or wire-feed welder, position the welding gun angled back from the starting point and start the arc and the wire flow. As you weld, observe the puddle of molten metal and pull the tip of the welding gun in small back-and-forth motions along the welding seam. You will leave behind cooling weld. As with a push bead, keep your motions and your travel speed even. Pull welds with MIG welders on aluminum are not recommended, because the gas cloud tends to dissipate and can result in a porous or dirty weld bead. With a stick welder, strike your arc and then angle the stick away from the weld. Move the rod in small motions, leaving the puddle behind to cool. Be careful of your arc length, as it’s harder to maintain proper distance when pulling a stick weld.
If you’re using a TIG welder, pull welding is not recommended. But to try it for yourself, angle the welding gun away from the start of the weld as you create the arc. Observe your puddle and push the molten material into the arc as you dip the welding rod. Pull the arc along the seam with small motions, coordinating the rod and the gun motions. Again, mind your arc distance closely when pulling a weld.
To pull with an oxy-acetylene welder, work your puddle backwards with the flame and push it with the dipping action with your welding rod. This adds material and pushes the puddle to the area being heated by your flame.
How Not to Warp Your Work
Like most materials, metal expands when it is heated, and it contracts as it cools. If you heat part of a piece during welding and then weld another part as the first part cools, the different rates of expansion and contraction in different parts of the structure will cause the assembly you’re making to warp. The problem is more pronounced in smaller, thinner parts because more of the mass of the object is being heated.
Warping happens mainly when too much weld is applied too fast. If you run a long bead on one seam, then try to run a second long bead on another seam, you are at risk of warping your structure.
To help reduce warping, stitch your beads in 1-inch increments at spaces throughout your weld seam. Let each area cool as you weld in another place. Eventually you will join up all your stitches and your piece should have minimal heat distortion. You can also backstitch a project by starting about an inch from the end of the weld and welding to the end. Then start again 2 inches from the end and connect to your previous weld, and so on through the length of the bead.
Generally speaking, sheet metal is thinner than .125 inch, and referred to more often by its gauge than in terms of inches or millimeters thick. Metal that is .125 inch or greater is generally called plate. Sheetmetal is one of the most challenging materials for an amateur welder. Because it is thin and light, sheetmetal is easily warped, and it’s easy to melt it and blow a hole through the material with your welder. Low welding power is required to protect the material, but this can make it hard to start and maintain an arc.
When working with a MIG or wire-feed welder on sheetmetal, tack the materials together in many places to get the positioning established, then run stitch welds carefully. Try to keep your arc focused on the heavier metal if you are welding sheet to heavier stock. Finally, join your welds up into a bead.
If possible, use TIG welding on sheetmetal, because the adjustable foot pedal power delivery makes it easier to start an arc and give it just enough power to make the weld. The fine point of the tungsten electrode also helps focus the arc for precise work.
Gas welders can also be used with success on sheetmetal, but they take more experience and finesse than a TIG unit. Using a stick welder on sheetmetal is nearly impossible. It can be done by an expert, but it’s hard to do without burning holes in the material.
Making a Heavy-Duty Shop Cart or Welding Table
Every shop needs a rolling cart, engine stand, or table, and a welding shop absolutely needs a steel-topped table. This basic structure is strong enough to serve as an engine cradle for a big-block V-8, or add a steel plate to the top to make your own welding table. You can weld on casters if you desire mobility, or keep it as a basic table.
For the purposes of the project, we assume you’re using a DC MIG welder with gas and basic mild steel solid core wire. But you can undertake this project with a stick welder, oxy-acetylene, TIG, or wire-feed welder and still get good results.
These instructions provide measurements and dimensions for a small (24 x 48 x 33 inch) structure made of 1.5-inch .095-wall square box steel, but you can easily create a larger model by extending the relevant dimensions. Follow these steps:
1: Get a supply of 1.5-inch .095- wall square box steel. For this project, you need two 8-foot lengths or one 16-foot, and two 10-foot lengths or a 20-foot length. The overall lengths are important to avoid waste. Metal supply yards may have the material in 20-foot lengths, but generally make at least one cut without an extra charge, and this makes the pieces easier to carry home and use.
2: For the basic project, you can make 90-degree cuts. This leaves the ends of the tubes open. For a more advanced project, you can make 45-degree cuts on the pieces that comprise the upper and lower rectangles. This makes a tidier looking finished project. Use your chop saw or hacksaw and cut your steel into the following lengths. Make sure all pieces of a given length are identical:
- Four 48-inch lengths (cut 8-footers in half)
- Five 24-inch lengths (section a 10-foot length)
- Four 30-inch lengths (section a 10-foot length)
3: Clean up your cut ends on a belt or disc sander, and put a slight bevel on the outside edges. This helps provide your weld a place to build up without protruding much past the original size of the tube. Give them a nice bevel but don’t take too much material off— you need enough remaining to make a solid weld.
4: Arrange your base rectangle on your welding table or another flat surface, such as a solid workbench. Use your welder’s magnets, carpenter’s square, and tape measure to make sure the rectangle is true. You can check for true in any rectangle by measuring on the diagonals. Both diagonals will measure the same when all your corners are at 90 degrees and the lengths of your pieces are correct. There may be some gap at the joints, but that’s less important— you can fill that with weld.
5: Carefully tack weld the four pieces together—just enough to hold them in place! Then measure again to make sure you didn’t disturb your angles. If all is good, then start running beads. Alternate corners and measure your angles again after each bead. You’ll be surprised how much the structure moves as you weld!
6: Repeat steps 4 and 5 for the second rectangle that makes up the top support of your table or cart. Add a third 24-inch piece across the center of this rectangle.
7: When you’re done, set the second rectangle on top of the first. They should be identical, or nearly identical. Remove the second rectangle and use your welder’s magnets and a spirit level to set up one of the four 30-inch pieces vertically on the lower rectangle. Tack weld it and re-measure with your spirit level. Then repeat this step for the other three corners. Remember to tack weld only at this point—no beads!
8: Set the upper rectangle on top of the structure. The structure should be level and the four posts should be square against the corners. If it needs adjustment, a few light blows with a lead or bronze hammer should adjust it. It’s OK if you break a tack weld or two—just re-level and retack your piece. When you’re happy with the structure, tack the top rectangle to the vertical supports.
9: Give your structure one last go-over with your squares, levels, and tape measure. If everything is still good, go around the structure and weld beads on all the appropriate seams. Alternate corners, sides, and so on until all raw edges are welded. Alternating helps stop heat-warping.
10: Now you have a basic box. You can now choose to weld on a plate of steel (use at least 1/4- inch-thick plate) to make it a table or you can fabricate and weld on some supports for an engine or other heavy item. You can also weld on some heavy-duty casters to allow it to roll around.
If you decide to make a welding table, you may also want to drill some holes in one corner to bolt on a machinist’s vise, or weld on some hooks to hang other tools such as your chipping hammer or a wire brush. Other common fitments include a section of tubing that you can use as a holster for your MIG, TIG, or wire feed gun. The attachments you put on your welding table are limited only by available space and your imagination!
Alternate Welding Table Designs
As an alternative design for the welding table top, consider getting some box tube or U-channel steel and spacing them about an inch apart for your table top. The advantage to this design is that it’s easy to clamp or bolt parts to the middle of the table. You can also cut with a plasma or gas torch right on the table top, if you position the cut over a gap in the table. You can also fit part of a bent or right-angle piece down in the gap while you work. Many welding tables use a half-andhalf design with part of the table made of a solid top and part made in strips. Some tables designed exclusively for cutting use a grid of thin plates on edge.
Bracing Your Welding Table
As an optional extension of this exercise, you can get some more 1.5-inch square stock or 1.5-inch round tube and cut it at 45-degree angles to create braces for your structure. As you cut and prepare, note how the braces must be cut at exactly the right angles to fit well and weld in cleanly. If you extended the size of the project to create a big rack, some bracing is a good idea. If you weld on a top plate to make a table, the plate itself is a strong brace.
Advanced Structural Welding Option: Closed Corners
For a slightly more advanced project, consider cutting the components of your base and top rectangles at 45-degree angles. This eliminates the ugly open ends of the rectangles and gives your project a professional look. But practice on some scrap until you can get consistent 45-degree cuts from your saw your professional project can look even uglier than open ends if your angles are all wrong, and truing up the angles can be difficult. Also remember that the overall length and width of your rectangles will be the measurement of the longer sides of each bar.
Welding Skills Practice: Thick and Thin Welding
One of the most common automotive welding tasks is to weld mounting tabs onto existing structures. This most often involves welding a thinner tab onto a thicker structural piece. For example, welding a window net mount onto a roll bar, or welding a bodywork mounting tab onto a ladder frame rail.
When you’re welding thick and thin pieces together, you must be careful to balance the heat placed in each piece of metal. If one piece is twice as thick as the other, then spend twice as much time with the arc on the thicker piece. Just remember that you have to spend enough time on the thinner side to get that piece up to welding temperature for good penetration.
Follow these steps to weld a basic tab onto a thicker piece of metal.
1: Get the two pieces set up in the orientation you want them. A welder’s magnet is generally very useful for holding a smaller piece to a larger piece while you work. Tack your pieces together carefully.
2: Position your welding gun so that the arc starts on the thicker piece, and establish your puddle primarily with the thicker piece and the filler metal you’re adding. As you run your bead, gently wave the welding tip side-to-side to attach the thicker piece to the thinner piece. Most of the motion should cover the thicker piece.
Written by Russell Nyberg & Jeffery Zurschmeide and Posted with Permission of CarTechBooks