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Tack or spot welding 1/8 in thick mild steel

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  • Tack or spot welding 1/8 in thick mild steel

    I am new here and new at welding. I took a class last fall but our class had a less than desirable instructor.
    ​​​​​​
    i am looking to just tack weld a couple pieces of 1/8 in thick 1/2 in wide mild bar steel together. I am drilling a hole on one piece then laying the other piece on top and filling in the hole with flux core weld. I had a 125 amp welder but it didn't work. I did clean the spot with a weld brush before I started to make sure it was clean and shiny. Seems it wasn't enough power to make the weld strong enough and I could pull the 2 pieces apart.
    could you experienced welders out there advise me on what kind of gaseless welder I could use to do the job? What's the least welder I could use? I'm not looking for an overkill welder and I don't have to have the weld look pretty as it will be hidden.
    Any suggestions?

    Thanks in advance,
    Jess

  • #2
    Originally posted by Jessie126 View Post
    I am new here and new at welding. I took a class last fall but our class had a less than desirable instructor.
    ​​​​​​
    i am looking to just tack weld a couple pieces of 1/8 in thick 1/2 in wide mild bar steel together. I am drilling a hole on one piece then laying the other piece on top and filling in the hole with flux core weld. I had a 125 amp welder but it didn't work. I did clean the spot with a weld brush before I started to make sure it was clean and shiny. Seems it wasn't enough power to make the weld strong enough and I could pull the 2 pieces apart.
    could you experienced welders out there advise me on what kind of gaseless welder I could use to do the job? What's the least welder I could use? I'm not looking for an overkill welder and I don't have to have the weld look pretty as it will be hidden.
    Any suggestions?

    Thanks in advance,
    Jess
    Your 125 amp welder should have done the job, so I suspect the problem was in your technique, especially if you had a good hole size (3/16'"-1/4") If your hole size was too small or your heat too low, your hole likely filled up before your penetration reached the bottom piece. With a larger hole, you can weld around the edge and then fill the center to get good penetration.

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    • #3
      Thanks Northwelder. I appologize for another question for the same thing. It could be that is what the problem is. Any solutions?

      Comment


      • #4
        Do I continuous weld till it's filled or stop & go as I fill it being careful not to let it cool too much in between?

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        • #5
          I'm having off and on success. Not consistent yet

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          • #6
            Originally posted by Jessie126 View Post
            Do I continuous weld till it's filled or stop & go as I fill it being careful not to let it cool too much in between?
            With FCAW, if you stop and go, you will probably get slag inclusions and a weld that will fail. it would best if you get a heat setting that will allow you to weld continuously, so that all flux floats to the weld surface. If you stop, you should clean off the flux before re-starting.

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            • #7
              My old Lincoln handbook says that a hole for a plug weld should be 1.5 to 3x the material thickness. More on the thin stuff, less on thicker stuff.

              1/8" plate, 3/8" hole. 1/4" plate, 3/4" hole. 1" plate, 1.5" hole.

              You could try preheating the piece(s), especially the one without the hole.
              --- RJL ----------------------------------------------

              Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
              -------------------------

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              • #8
                Originally posted by Northweldor View Post

                With FCAW, if you stop and go, you will probably get slag inclusions and a weld that will fail. it would best if you get a heat setting that will allow you to weld continuously, so that all flux floats to the weld surface. If you stop, you should clean off the flux before re-starting.
                Thank you for that Northwelder. I seen a you tube video on this guy who welded holes and he imtermidently welded a hole and it worked but he was only welding one piece of steel with small holes not like what I'm trying to do that's why I figured I needed to ask you pros about it so now I understand what I cannot do

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                • #9
                  Originally posted by usmcpop View Post
                  My old Lincoln handbook says that a hole for a plug weld should be 1.5 to 3x the material thickness. More on the thin stuff, less on thicker stuff.

                  1/8" plate, 3/8" hole. 1/4" plate, 3/4" hole. 1" plate, 1.5" hole.

                  You could try preheating the piece(s), especially the one without the hole.
                  That is great information usmcpop! That's a good rule of thumb to go by. I will try preheating the non-hole piece and see what that does. It's the holiday weekend and I'm heading out of town but I will try this when I get back and come back here to post my results. Many thanks for your reply

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                  • #10
                    Does it have to be a plug weld? Is there another joint configuration you can use?
                    --- RJL ----------------------------------------------

                    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
                    -------------------------

                    Comment


                    • #11
                      Originally posted by usmcpop View Post
                      Does it have to be a plug weld? Is there another joint configuration you can use?
                      Well from esthetic purposes the 'hidden' weld looks better. We tried welding on the edges/ sides together but It's more work and more to grind. If we can get this 'hidden' weld to work it would be perfect.

                      Btw, I was looking what you posted earlier about the material thickness vs. hole size and we really can't go any bigger than 1/4 because the metal bars are 1/2 inch wide. When we tried bigger it would blow out the sides so 1/4 is the biggest hole size we can go.
                      ​​​​​
                      i did have a moment today to try the pre-heating the non- hole bar and it did seem to work . The weld held the 2 bars together. After the holiday I'm going to try it a couple more times. It just may be the solution.
                      Thanks again unmcpop.

                      Comment


                      • #12
                        Originally posted by Jessie126 View Post

                        Well from esthetic purposes the 'hidden' weld looks better. We tried welding on the edges/ sides together but It's more work and more to grind. If we can get this 'hidden' weld to work it would be perfect.

                        Btw, I was looking what you posted earlier about the material thickness vs. hole size and we really can't go any bigger than 1/4 because the metal bars are 1/2 inch wide. When we tried bigger it would blow out the sides so 1/4 is the biggest hole size we can go.
                        ​​​​​
                        i did have a moment today to try the pre-heating the non- hole bar and it did seem to work . The weld held the 2 bars together. After the holiday I'm going to try it a couple more times. It just may be the solution.
                        Thanks again unmcpop.
                        With what they say about to many cooks in the kitchen, I'm keeping my mouth shut until you post a picture? Click image for larger version

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                        Unless of course you have a darn good reason not to.

                        Comment


                        • #13
                          Originally posted by usmcpop View Post
                          My old Lincoln handbook says that a hole for a plug weld should be 1.5 to 3x the material thickness. More on the thin stuff, less on thicker stuff.

                          1/8" plate, 3/8" hole. 1/4" plate, 3/4" hole. 1" plate, 1.5" hole.

                          You could try preheating the piece(s), especially the one without the hole.
                          Why would a 1/8" thickness require preheat, unless ambient temp. is very cold?

                          Comment


                          • #14
                            Originally posted by oldguyfrom56 View Post

                            With what they say about to many cooks in the kitchen, I'm keeping my mouth shut until you post a picture? Click image for larger version

Name:	grumpy_old_men-461164.jpg
Views:	164
Size:	28.8 KB
ID:	705919

                            Unless of course you have a darn good reason not to.

                            Comment


                            • #15
                              I'd drill a 1/4 inch hole, probably even chamfer it a bit just because a 1/4 hole is pretty small compared to the tip. don't stop till you've got a nice button built. Short stickout.

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