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Type of joint (lap, butt, cope)?

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  • Type of joint (lap, butt, cope)?

    I am getting ready to start a trailer project and ran across this forum a few days ago. I am impressed at both the talent and patients here. Good group of people.

    I am familiar with both Stick and Mig welding and have done both. I am no where proficient with either but seem to get the job done in a hobby/ad-hoc fashion.

    The trailer project I am starting is a smaller 10x5 #3500 axle utility trailer. Main use for hauling camping supplies with a utility shell atop.

    It will be constructed with 2 x 3 x 3/16 angle.

    The machines I have available to me are:

    Mig - Dayton 90/110 amp ac/dc
    Stick - Miller dialarc 250 ac/dc

    My primary question is what kind of Joint would be recommended for this project?

    Mitered butt joint, lap joint or a coped joint. Maybe this is a matter of taste, but I would like to make sure that there is not a structural reason for each type before I discount them.

    On a side question, or maybe it has to do with the type of joint used, I would like to use the Mig as it seems to be easier but I don't seem to be getting good penetration on clean metal (3/16"). I am using flux-core wire. Does shield-gas wire get better penetration?

    It is harder for me to see what I am doing (can't see the joint with an auto darkening #10) but I read in other threads that I will probably need a stronger work light and use one of those white weld pencils to mark the joints and

    I hope what I am asking makes sense. I really want to do a good job since I will be pulling a trailer down the road and would rather not have the thing fall apart on the first (or umpteenth) bump.

    Thanks for any advice.

    I forgot to mention that the joints I asked about are for the bed frame corners. Forgot that only my Wife could read my mind (intentions).

    Last edited by FutureShock; 05-12-2009, 02:14 PM. Reason: Add forgotten detail

  • #2
    The little Migoline machine tain't enough- switching to Solid Wire and shielding gas makes it even a worse choice.


    • #3

      It seemed a little to dainty for the task at hand.

      Looks like i will be sticking to.....well stick. (pun intended)



      • #4
        You can use a lighter shade in yer helmet also.

        Shade # is for Comfort.


        • #5
          Welcome to the forum Future Shock. Best of luck with your project.

          Don't feel bad about using stick to fabricate your trailer; I know several experienced, unhurried fabricators who prefer it. Just be sure your weld quality is up to it; lots of liabillity here. Suggest you have your plans checked by an experienced fabricator too.

          As far as joint type vs strength is concerned, lapped joints are strongest of course and are employed by many trailer fabricators. Between mitered/butt welded joints and coped joints there should be no difference in strength when properly done. If you're planning to build your trailer with low sides (vs a true flatbed) to give it enhanced rigidity, you can use upright angle spanning the corners for part of the rail or side support. That will give the corner joints extra strength and at the same time provide the best mounting possible for the sides. With the size of angle you're planning to use, I would build a trailer with at least low sides. A true flatbed would be better built with something heavier.


          • #6
            Thanks Broccoli1.

            Next time I use the Mig I will try a lower #.

            I was not sure how low they went or if it could be a danger.



            • #7
              Thanks for the input Dmaxer.

              I have purchased the trailer plans, I did not feel comfortable trying that on my own.

              Since it will be a sided trailer with 17" sides, I like your suggestion with the corner post. Gives a few extra welds for strength.

              I feel somewhat comfortable with my stick welding. I can get good penetration, its just I need to work on the looks of it. But I suppose that's why they made angle grinders. hehe.

              And since I have until August to get it done, I can take my time and do some practicing. It's that dang liability thing that stays on my mind. Nothing worse then leaving a bread trail of 2x3 angle iron in your path...... well I guess unless it's the guy in front of you doing it.



              • #8
                On anything i do 7 out of 10 times i use a but joint with a plate on the out side of the welds.


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