Multiple passes?

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Sorry if this is a basic question, but how many passes should be made when welding something, and how do you determine this? I'm just using a HF 90amp fluxcore mig and not welding anything over 1/8"It seems to my inexperienced eyes like one pass does the trick, and any more than that I'm just piling up the weld on top of itself. ThanksI'll get more pics, but this is the only one I have right now. Just a single pass (and I didnt think to take a pic till after the first coat of paint)
Reply:Number of passes is determined by many things. #1 would be whatever specs the engineer etc listed in the welding procedure for the project. Size of the machine and electrode used also plays a big part in this.For the home hobbyist usually 1 pass is about all you can do on average with the equipment available. More passes with a small machine won't equal the strength of a larger machine. While it is theoretically possible, there's a lot more to it than simply piling more weld on the project. The issue with small machine is that they lack the power to get a good deep bond with the base material.Any subsequent welds are still only being held by the original base layer that is usually inadequate for heavy materials.On average with a fillet joint ie T, lap joint or properly prepped outside corner, you only need the legs of the weld to be equal or slightly greater than the thinner of the base material thicknesses. So for 1/8" steel, you would want the legs to be say 1/8" to maybe 3/16" max for full strength. Welding up a 1/2" or 3/4" weld won't increase your strength at all. In some cases it may actually weaken the base material and cause the joint to fail right next to the weld.One exception to this would be open root joints with 7018. here usually they will weld a root pass with 6010/11 to close up the root, and then weld it out with 7018. This is because 7018 will develop porosity because the back of the weld is unprotected, not because more passes makes it stronger. Using 6010/11 with 7018 isn't needed on closed root joints like fillets, and actually can weaken the joint since the 60XX rod is weaker than 7018.With your small 90 amp FC machine, you will be limited in what thickness you can weld under real world conditions. 1/8" is pushing the max and 14 ga would be a better real world max for things that are critical. If all you are doing is sticking two pieces together for art etc where strength isn't a factor, then you could use it on thicker materials, but more welds won't really reliably increase the joint strength much..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:If u get bitten with the welding bug, you will be looking for a bigger and better machine very soon.   Everything DSW said is spot on.Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Thanks for the time it took to type that out DSW. I figured this was the case."Any subsequent welds are still only being held by the original base layer that is usually inadequate for heavy materials."And Southpaw, yes I've been bitten by the bug. This was a gift, but I'm already saving up for something better. For now I'm just tinkering around. Fixed my rusted out bbq grill stand, made a small patio table, etc. I'm definitely staying away from any large stuff. Especially if it needs to be load bearing or structurally sound!