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A # of MIG welding ?'s for y'all. Please help.

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  • A # of MIG welding ?'s for y'all. Please help.

    First off I have a MM200. I am very new to welding, about 2hrs total.

    1) I noticed on the machine that there is a + and -. Is there some sort of reverse polarity MIG welding? If so, what would you use it for?

    2) If I use an extension cord for the welding machine, will length matter? I do not want to restrict any voltage from the m achine that will cause any problems.

    3) Dialing in a the MM200, if you dial it in correctly to weld some 1/4" mild steel, could you go back to those settings everytime you would happen to weld some 1/4" MS?

    4) If you are joining two different thickness metal, say 1/4" and 1/2", what would the process of welding them correctly be? Would you focuse the center of the bead more on the 1/2" to ensure the penetration is good?

    5) When buying contact tips, does the brand matter, or are they all made the same, just different sizes?

    6) What size mild steel metal could you weld using .023, .030, and .035 wire? Are there any other sizes?

    I am sure there will be more ?'s to come. Thanks in advance for the detailed information
    They don't call me Lucky for nothin'.

  • #2
    Hey there lucky im gonna answer your questions in the order they came to the best of my ability.

    1.) For mig welding the polarity is the same as stick welding, there is a dcep (dc electrode positive) and a dcen (dc electrode negative). dcep is also called reverse polarity and dcen is also called straight polarity. In mig welding dcen is used for welding very thin materials as i was told, and dcep is used for regular welding.

    2.) when it comes to the extension cord length does matter. For my little red mig they only recomend a 50' extension cord max, but im not sure as to why.

    3.) as far as i know once you find a setting that works good for something write it down somewhere. That exact setting may not work perfetly every time but it will give you a general or rough idea of where to start. From there its usually just tweaking the voltage and wire speed a little bit.

    4.) When it comes to welding materials of 2 different thicknesses ive heard two or three different stories. What i was taught was to focus more on the thicker material. THat changed when i got to one job where i was told and shown what happens when you do that. I focused the weld on the thicker material and the weld began to crack. This was due to improper fusion or heat being focused too much on one member. THis was because i focused on the thicker member more weld got on it than the thinner one. I was then told to put equal amount of weld on each of the members.

    5.) when it comes to buying contact tips i dont think brand does matter. I just always bought the brand that came with my welder but i do know that alot of tips are interchangable or compatible with other guns or companies make tips for guns. AT work all of our tips are made by KENT but our guns are Bernard.

    6.) When it comes to picking a welding wire size it all depends on what sixe of material you will be welding. If your gonna be welding sheet metal go with .023. If your gonna be welding say 1/8 to 1/4" i would go with .035 or .045 it depends on preference.

    I hope this great big long novel will help. If anything is unclear i know there are tons of people on this board who are more knowledgable than me and could clear things up.



    • #3
      1) You would use DCEN for gasless flux core wire only - NOT thin metal welding

      2) The length of the cord will depend on it's gauge. generally the heavier the gauge, the longer the cord can be, within reason.

      3) Yes the settings will produce repeatable results.

      4) Do not focus more on the thicker piece unless, you are burning through the thinner peice and can not reduce the power without sacrificing penetration on the thicker peice.

      5) If the contact tip is the correct length, gauge and thread then it will work, no matter what brand. The main tip difference in consumer welders is the thread pitch.

      6) .023 is generally for sheet under 1/8", .030 is good up to 1/4" and .035 will weld up to 3/8"
      Last edited by TS-Off-Road; 08-28-2007, 02:35 PM.


      • #4
        As TS said. Also:

        1) DCEP generally for MIG (that is, solid core, with gas).

        2) Wire has impedance (read that "resistance" for the sake of discussion). Thicker (i.e., heavier gauge) wire has less resistance than thinner wire. That resistance causes a voltage drop, using power just to get the electricity from the source to your equipment. (Current has to work harder to "get there" with more resistance facing it.)

        You had a recommendation for a max. of 50' of a particular gauge of wire because a greater length than 50' at that gauge would drop your voltage below the efficient operating voltage of your equipment . . . making your equipment work harder than it should, and making it get too old too soon.

        Just for sh*tz and giggles, think about using a grocery store extention cord to power your welder. Think about how quickly that cord would heat up and melt its insulation. (Or try it, if you're into running to the service disconnect and flipping breakers . . . after you put the fire out.) Go in the opposite direction gauge-wise.

        TS said you could get more length by using a heavier gauge cord, within reason. That's right on point. Exactly how much longer depends on a lot of factors we don't know, but you could figure this out from a standard NEC wire gauge chart. You can also confirm your calculations with an off-the-shelf volt meter.



        • #5
          Originally posted by TS-Off-Road View Post

          2) The length of the cord will depend on it's gauge. generally the heavier the gauge, the longer the cord can be, within reason.

          4) Do not focus more on the thicker piece unless, you are burning through the thinner peice and can not reduce the power without sacrificing penetration on the thicker peice.
          2) For your MM200, try to use a 10ga extension cord (12ga MINIMUM!) and try to keep it under 50' or so. If your outlet/breaker will handle it, you can conceivably go further than that, but at 100' you're going to lose some available amperage on the upper end. In other words: you could use a 100' 10ga extension cord with your MM200 if you were welding 1/4" thick mild steel.

          4) It will take more room than we have in this thread to describe to you all the different methods of using your MIG gun to achieve your desired results. If you can envision a "weaving" pattern, then weaving back and forth between your two dissimilarly-sized pieces should be okay. If you will pay very close attention when you're welding, you'll see that as the wire comes out of your gun/nozzle and makes contact with the metal, your resulting "puddle" of molten metal is a good bit wider than the actual piece of wire that's creating that puddle. Now, the object is to get even "coverage" into the gap between the two pieces of metal...even when they're different thicknesses. However, sometimes you'll notice that your thinner piece begins to "burn away" from the joint with the thicker piece. When this happens (and it will), you're going to need to make minute adjustments with the angle of your gun so that you're "shooting" your wire a little more towards the thicker piece than you are towards the thinner piece. The difference in your "aim point" may not be any greater than 1/16" of an inch or even so little as 1/32" of an inch, but with practice you'll be able to see how even a slight difference in aiming/shooting will allow you to maintain the same size puddle on both pieces of metal.

          Is this all making some sense to you yet?
          Last edited by BWS29128; 08-27-2007, 08:56 PM. Reason: EEK! Improper grammar!!
          Clint Baxley
          Baxley Welding Service
          Rembert, SC 29128


          • #6
            Wow, thanks for the prompt and detailed responses! I will post up some pictures when I make the first bead at school tomorrow. Thanks again!
            They don't call me Lucky for nothin'.


            • #7
              let me see if i can remember this correctly to explain why an extension cord has to be the correct size for the distance and current being carried.lets see in a simplified way, it works like this;
              Volts X Amps =Wats
              resistance reduces the volts, the smaller the size wire in the cord the more resistance. but the V X A = W formula has to work. so if you have a 1500 wat weed eater (120V X 12.5A =1500W)and you decide to do the fence out back of the neighbors yard by adding 200 ft of 16 gage extension cord to get you there the small wire size and long distance is going to have a high resistance, so it acts on the volts dropping them to say 80V. well the weed eater still needs 1500W to spin up and cut the weeds. but at 80V it takes 18.75 amps to get the needed 1500wats. problem is the motor is only designed to take 12.5 amps, so it overheats and burns up.

              if you download the owners manual from the miller site it should give you a recommended extension cord size per the distance you want to go, well up to a point any way.

              i have a few 14gage extension cords around for lights but anything else gets a 12 gage cord. i don't even but the 16gage ones they sell at wally world for outdoor use, yea like thats going to work. i always tell all my Friends to get rid of the stack of silly little cord they have in the garage and get a few good 12gage ones. it will extend the life of all your tools. drill's, skill saw's, saws-alls, you name it, they all need a good cord to work properly. without it they have to work extra hard to get the job done.
              thanks for the help
              hope i helped
              feel free to shoot me an e-mail direct i have time to chat. [email protected]
              summer is here, plant a tree. if you don't have space or time to plant one sponsor some one else to plant one for you. a tree is an investment in our planet, help it out.


              • #8
                Good advice James and Clint.
                Now I will add my 2 cents worth.

                When you are thinking about extension cords, think short and fat. In other words, the wire with the larger diameter and shorter length would be best. As current travels through a wire the wire offers resistance and this produces heat. The more current traveling through a given wire size, the more heat. This is why these very cheap, small, dime store extension cords are so dangerous. Place a heavy load on one and they heat up, the insulation melts, the house burns down and the insurance company is mad. This is why the NEC (National Electric Code) states that at no point along the wall of a house shall be more than 6 feet from a receptacle. You can see from this that the National Electric Code does not want you to use ANY KIND of extension cord in a house. If you are in a room and the receptacles are not more that 6 feet apart, and you are in the middle of them, there is one 3 feet on either side of you. All electric appliances you buy at Wall Mart will have a cord longer than 3 feet, even those made in China. So in theory you don’t need anymore extension cords in a house if your house is wired to meet the code.

                As mentioned above it is current going through a wire that produces heat when it meets the resistance in the wire. So if we could get the same about of electrical work using less current, we would heat up the wire less and this would be good. Can we do this?? Yes, Power = current x voltage. You can see from this that if you double the voltage you can get the same amount of power with half the current. That is why if you wire a pump for 220 instead of 110 you can get by with smaller diameter wire. In the paper mill where I worked we had many motors than ran on 2300 volts and some that ran of 13000 volts. Can you imagine the money saved on copper because of the smaller wire size this allowed?

                Now we can look at wire length. All equipment is designed to operate at a certain voltage. In our homes it is 110v and 220 volts. If the equipment sees this voltage it is happy. Most manufactures allow no more that a 10 percent deviation from this nominal voltage. Go over this and the light burns dimmer, the resistance heater puts out less heat, the transformer puts out less power ( less power in = less power out ) and electric motors become less efficient, begin to heat up, begin to burn up. YIKES !!! This is why correct voltage is so important.

                Now back to the length of the extension cord. Think of voltage in a wire pushing current as pressure in a pipe pushing water. The longer the pipe you are pushing the water through, the more pressure drop you experience and the less water you get out the end. It is the same with wire. The longer the wire the more voltage drop you are going to get, because the longer wire offers more resistance. There is a formula for this: current times the resistance = voltage drop. From this formula you can see for any given size wire and any given current, if you double the wire length you double your voltage drop. In other words there is a direct relationship between wire length and voltage drop.

                Now to sum it up, if you want to limit your voltage drop there are 3 ways to do it. Use a shorter piece of wire ( extension cord), use a larger gage wire, for instance, 10 versus 12 or 12 versus 14, and limit your current. The last thing is for the circuit rather than the extension cord. If double the voltage you can cut the current in half, i.e. 220 volts versus 110 volts.

                My suggestion would be use 2 shorter extension cords instead of one really long one. 90 percent of the time the one cord is all you will need so you will see half the voltage drop. And don’t cheap out on the extension cord. Buy a heavy duty cord. You don’t want to damage expensive welders, grinders etc. because you wanted to save a few dollars on an extension cord.

                I know this is probably a lot more than you ever wanted to know about extension cords and I am sorry it is so long. Once I get started on something like this I go a little crazy. Also, when using extension cords always use a GFI. Besure to plug the GFI into the receptacle and then the extension cord into the GFI. This way you are protected if the extension cord is defective
                ( bare wire ) and you get a hold of it. I use to tell people that worked for me that having worked around high voltage for many years, the closest I have ever come to seeing somebody electrocuted has always been when they were on the ground or working standing in water and using an extension cord on a 110 volts.
                sigpic 6010
                If I had know I was going to live this long, I would have taken better care of myself.


                • #9
                  2/4 Done, Now 3/6

                  I think Questions #2 and #4 have been answered, so now let's look at Questions #3 and #6 regarding proper MIG settings. Here are a couple of links that will explain it better than we can on here:

                  Those should keep you busy for a little while...


                  Also, last but not least: here's the link to all Miller's Owner's Manuals. Download a copy for your machine and you'll be that much further along in the ballgame. ~cmb
                  Last edited by BWS29128; 08-28-2007, 09:31 AM. Reason: Incomplete Information/Additional Info Found Relevant
                  Clint Baxley
                  Baxley Welding Service
                  Rembert, SC 29128