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Thread: 1/16 aluminum plate to 3/8 aluminum bar...HOW?

  1. Default 1/16 aluminum plate to 3/8 aluminum bar...HOW?

    Hey guys,

    Any suggestions for tacking 1/16" plate to 3/8" bar (aluminum). Using tig. I was thinking of cutting little wedges out of the bar to fill the gap between the two. This is not a real structural build more like a sign project.

    Thanks for suggestions and ideas,

    The tig kid

  2. #2


    Not sure what the problem is? Is it the difference in thickness? Or is it poor fitup.

  3. Default

    Quote Originally Posted by joshuab View Post
    Not sure what the problem is? Is it the difference in thickness? Or is it poor fitup.
    Imagine a shape cut of 1/16" aluminum with 3/8" round bar laying on it, there is a large gap between the round and the flat surfaces.

  4. #4
    Join Date
    Dec 2013
    Chandler, Arizona, USA


    I'm going to say... Instead of laying the "sign" face-down and placing the 3/8" rod on top, stand the sign up on edge with the 3/8" rod horizontal so gravity works with you to draw the puddle into the gap. Start your puddle on the thicker material, and add plenty of filler while you work the puddle over to the 1/16" sheet.

    Unless you need a full weld, I'd stop after a few large tacks.

    210EXT (2013 USA)

  5. #5
    Join Date
    Dec 2009
    Greater Seattle, WA

    Default 1/16 aluminum plate to 3/8 aluminum bar...HOW?

    Put tungsten into the gap (as deep as is practical with good vision and filler rod access - don't sweat about going too crazy deep), light up a high current arc to make two shiny puddles at the same time, jab aluminum filler into them to plump them up and make them bridge across into one. (Optionally you can make just one puddle and build it closer to the other - no need to do it all in one step). Then after you make the first tack, progress the arc down along the joint, and you should see a "C" shaped puddle. Control penetration by seeing how deep crotch of the "C" is (no need for very much penetration welding 1/16" sheet - in fact, too much will melt through and warp). Back to the molten "C", plump it up, progress further, and repeat. It's up to the design at hand whether to do skip welds or continuous. If the 3/8" rod supports the sign and extends away from the sheet, where the sheet ends will be a stress riser, so important to get good welds on both sides of the rod down there. The rest of the rod-sheet interface seem like the rod will just provide some rigidity to the sheet material, so you can probably do just tacks welds or short skip welds staggered alternatingly along the sides.

    To avoid melt-through from over penetrating the 1/16", you will want to keep the work cool, weld with adequately high current to avoid heat soak and keep your puddle controllable, and jab that filler in there QUICKLY as soon as you see that 1/16" puddle.

    I'd suggest welding flat on a flat metal welding table (if available) to evenly support the sheet, dissipate heat, and provide backing for the thin sheet. If you have a big piece of copper, aluminum, or stainless bar or flat stock you could also put thar behind you are welding, and clamp it together as a backer. (Clamping will also help keep things from moving around when you are going for your first tack.)
    Last edited by jakeru; 02-26-2014 at 07:52 AM.
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  6. Default

    That's what I was looking for.

    Thank you jakeru,

  7. Default

    WOW! jakeru has described that Very well (almost felt like I was seeing it )

    I would just add two things. I would "lean" the torch towards the 3/8ths piece, concentrate the heat on IT, maybe start the weld on that side and once a puddle is established there, run it to the 1/16th and proceed like that the whole way.

    And, with Aluminum in general, the problem we have is that it takes a "practiced eye" to recognize when things are just starting to go wrong (unlike steel where you get a color change towards White and "sparkling"). Things happen Fast, too much heat in the piece has accumulated as you get to a place where it's no longer being dissipated or it's just "built-up" and backing-off the Amps alone isn't gonna save it... But Filler Rod might! Be prepared to stuff 1-1/2" of rod into the puddle at any time! -hehehe...

  8. Default

    drill a couple holes in the 1/16 plate in line with where you want it attached to the 3/8 round stock. Then just weld the hole shut making sure you melt the weld into the 3/8 so that they are welded together . 2 holes should hold it together as good as bolting it.
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