Tag Archives: metal fab
One of the simplest welding joints is the butt joint. It is not the strongest, but it is one of the most useful especially for automotive body work. This type joint is used whenever you butt 2 pieces together and then weld between where the two meet. Butt welding thin sheet metal can be complicated because thinner metal has a tendency to burn through on the edges. This doesn't mean it's impossible, just that there are techniques that can be used to minimize these issues.
Because the edge of a piece of metal absorbs heat faster than a solid surface, you need to modify your technique with the electrode. Whether you are using wire feed, stick or TIG welding, you need to move the electrode quickly and dance around the weld area, to avoid burn through. With the stick welding technique, this can be done using a stitch welder, which moves the electrode in and out like a sewing machine needle when you pull the trigger.
When done properly, a butt joint should show bead on both sides of the metal. One way to help insure this is to clamp the 2 pieces with a uniform gap between them. The Eastwood Butt Weld Clamp and Backer Set holds sheet metal slightly apart for better weld penetration and also helps hold the work tight to prevent warpage from the heat. These clamps also help to prevent crawl, which occurs when the metal tries to move away from the heat of the work area.
Even with clamps, the first step in a butt joint is to tack weld along the entire length of the joint. Start with a weld every few inches, at a uniform distance, then go back and fill in with more tack welds between the first set. Before moving on to the final bead you should have welds about an inch apart along the entire joint. Even with this technique, there will be some distortion that needs to be hammered out afterwards, but this will help minimize it.
Some welders prefer to use a weaving/zig zag or circular technique with thinner metals. This leaves you with a wider bead than you need, but it helps to spread out the heat of the weld to minimize burn through and warping. Before doing butt welds on something important, practice different angles with the electrode, rate of travel of your welding and length of your arc until you are comfortable with the thickness you need to weld, and establish your technique to avoid burning through it.
The picture above shows 4 different welds in cross section that you are likely to see when making TIG welded butt joints. Figure B shows correct technique, while examples A, C and D have various issues.
A: A common mistake beginners make is to pile too much bead on the top side of the joint, in an attempt to keep from burning through. This can be because the weld was not hot enough or more likely because the electrode was not close enough to the surface for proper penetration. For a butt joint to be acceptable, the bead should envelope both edges on both sides of the work, so no trace of the original edge can be seen.
B: This is an example of the correct penetration of a butt joint. There is bead showing on both sides of the work, with the lower bead being slightly smaller than the upper weld.
C: When you have too much penetration, the weld will begin to show undercutting and take this shape. You can see how the bead has begun to sag through the joint and not fill the top side fully. Undercutting is where the thickness of the weld is actually less than the work being welded, which means a weak joint.
D: This shows even more penetration and undercutting; the top bead has taken an almost concave shape. This is an even worse example than the one directly above.
In addition to the common problems, there are also a few different ways you can prep the metal before it is welded. The following only really applies when welding metal 1/8" or thicker because any thinner and you will almost always burn through.
The first and most common is known as a square butt weld. This is done when two flat pieces are up against each other. this is used for thinner metals and TIG welding. If welding metal thicker than 3/16" this method should not be used because the weld will not penetrate far enough into the metal and will not be as strong.
The next type of but joint is known as a bevel or double V joint. This type of weld is a must when welding metal 1/4" - 3/4". When the edges of each piece are ground down it creates a valley or grove for the weld to sit in, this gives more surface area for the weld to bond the two panels.
The third type of butt joint is known as a double bevel or double 'V" and is the strongest type of butt joint. This type of joint is used in areas where weld strength is critical. This type of weld is usually used when welding metal thicker than 3/4" but can also be used on thinner metals if more strength is needed.
It is true that the strength of welds when doing butt joints to body panels is not as critical as when doing structural repairs. However, properly welded butt joints will make the repair look better with less grinding and body filler. A well done joint will also last much longer, while a poorly done repair may crack and ruin the paint and body work after just a few miles of driving. Because of this, it’s important to practice and get the underlying repairs correctly done before moving on to the next phase. Learn the proper butt joint technique, and you will use it on countless welding jobs.
So you are ready to get serious about your metal work, and you want to add a wire feed welder to your shop’s arsenal. Good for you, a welder is one of the most useful pieces of shop equipment. Below, we take a look at the features and specifications you need to think about before deciding which one is right for you.
Flux Core VS MIG
Wire feed welders actually consist of 2 different welding types: Metal Inert Gas (MIG) and Flux Core. Flux core uses wire with a hollow core that releases a shielding gas as it melts. MIG uses a solid core wire and a tank of inert gas which shields the weld from contamination. Nearly every MIG machine can do flux core welding, but not every wire feed welder set up for flux core can be converted.
Besides the lower cost, flux core welding does have other advantages. The flux does a better job of shielding in windy or dirty environments, so it’s great for field work. No gas and no tank – That means one less consumable to buy, and a smaller lighter unit to carry around if you take it to the job site or race track. Plus, flux core actually burns hotter, so it is actually better for welding thicker material.
There are several disadvantages of getting the lower cost, flux core only machine. First, flux core produces sloppy looking welds with lots of splatter, even in the hands of a pro. Second, because it burns hotter it is hard to weld thinner sheet metal without a lot of burn through.
So there's lots you can accomplish with just flux core wire, but, except for the lower initial purchase price, there is no reason to get just a flux core wire feed welder, when every MIG machine can do both. above you will see the suggested settings for the Eastwood MIG 135. The bottom two lines of the top chart show the suggested settings if using Flux core wire.
Choosing a MIG Welder
MIG welding (Metal Inert Gas) takes the basic method of wire fed flux core welding, and uses a solid wire instead, plus a tank of gas which provides the shielding. Many basic flux core welding set ups can be converted to do MIG welding with just a few parts. Typically, you need to add a gas solenoid, a regulator, and a tank of shielding gas, though some already come equipped with the solenoid.
MIG works just like flux core: you pull the trigger, wire is fed, and gas comes out the tip to shield the weld. MIG welding produces cleaner, neater, more consistent welds, especially at lower heats on thinner metal. MIG is also the preferred way to weld aluminum, though you will need a special aluminum spool gun, and a tank of argon.
110v VS 220v
This choice may be dictated strictly by where you are planning on using it; if your shop isn’t wired for 220v, or you plan on using it on the go, 110v is the choice for you. But there are some welding units out there that run on either voltage, with just an adapter plug. This is a great compromise if you are planning on rewiring your shop in the future, or already have 220v in the shop, but want to be able to weld anywhere and everywhere.
The Eastwood MIG 135 is our entry level MIG welder. It is perfect for the home user that wants a shielded welder but only has 110V power source. This welder is rated to 3/16" which is perfect for auto body and basic structural repair.
Moving on to the next level is the Eastwood MIG 175. This is a 220V only unit which means it will be able to weld thicker metal up to 5/16" steel. You may think that there is not much difference between the two but the big difference is the duty cycle. With the MIG 175 you will be able to weld on a higher setting for longer periods of time.
Lastly we offer the Eastwood MIG 250, this is a dual voltage unit and is internally controlled. This means that you don't need to change any settings when going from 110V to 220V, just simply plug it into the desired power source and the welder will adjust accordingly. On 220V this welder is rated to 1/2" steel, making it great for heavy structural welding.
But what are the advantages of the higher voltage? Obviously a higher voltage unit is more powerful than a lower voltage one; they typically can put out more heat and weld thicker materials. This is also important for welding aluminum, which requires more amperage compared to welding steel of the same thickness. If working with a lower amperage within the range of most 110v units, like 90 amps for instance, a 220v unit is going to have a much higher duty cycle. So, you’ll be able to get more done faster, with less down time.
The duty cycle for a welder is usually expressed as a percentage at a given amperage, 20% at 90 amps for instance. That is a typical rating for a home use 110v MIG welder, it means with the power set to 90 amps, you should only be welding continuously for 2 out of every 10 minutes to avoid overloading the welder. You could see how that would be an issue if you were building a bridge, or a tube famed chassis. A 220v machine is often rated at 30% at 135 amps, and something like 60% at a lower 90 amp setting. That means you can weld much longer without overheating the machine and having to take a rest.
Transformer VS Inverter
Years ago all MIG welders were transformer welders. They all used windings of wire to transform the 60hz AC voltage coming out of the wall into much higher voltage at the end of the welding torch, but still at 60hz. In the 21st century, there are now welders that use solid state inverters to step up the wave frequency of the electricity to much more than 60 cycles per second. Because of this, they can produce higher voltages with much smaller transformers. Since transformers are just windings of copper wire, the smaller they can be, the more portable the welding unit can be. The inverter technology also allows machines like the Eastwood 200 Amp MIG/Stick to exist because they can switch internally to the different electrical requirements of flux core, MIG welding and stick welding, and produce different shaped waves if need be.
Inverter based units also need much less energy to run. If you are planning on running your welder off of a generator the inverter is the way to go. Transformer-based units require a much larger generator in order to work. The extra money you spend to move up to the inverter unit is money you will save by buying a smaller generator. The lower current draw of an inverter unit typically means you can run it on an extension cord for easier use around the shop. Your electric bill will be lower too.
Some machines these days can practically set themselves up, while on the low end some just have “high” or “low” heat settings. Like all things, if you can’t adjust it to suit you, you are going to have to adjust to suit it. MIG machines usually have 2 important settings: wire feed speed and power. Most times the more power you use the faster you want the wire to be fed, but not always. The more basic machines usually have fewer settings, and typically are “stepped” or “notched” meaning you can’t choose a setting between 1 and 2. The better machines are infinitely adjustable; you can choose any setting between anywhere on the dial, not just the numbers 1-10. If you can’t find a setting that works with the speed you want to weld on the material you are working with, then you have the change your speed to suit the output you can get. This is where the fine adjustments can come in handy.
Parts and Serviceability
A welder ought to be a lasting investment, but buy a unit from a low cost generic brand that hasn’t been around for long, and you may find parts and consumables impossible to find in a few years. At Eastwood we have been here since the late 1970s and we plan on being here a long time, standing behind our products. Not only do we have quality welding units at an attractive price, but we also carry all the parts and supplies you will ever need for them, except for the gas, but if it was possible we would sell that as well. We sell replacement tips, wire, torches and more for our MIG welders. We also have technical support for you by phone and email.
We are committed to providing professional quality welding machines at a price the home hobbyist can enjoy. You can buy more powerful welders from other brands, and you can buy less expensive welders, but we don’t think you will find a better welder for less.