Mitered Outside Aluminum Corners
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  1. #1
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    Mitered Outside Aluminum Corners

    What are the methods you guys use on the outside corners on mitered aluminum tubing using TIG?

    The two edges are so thin that the easily autogenously weld together without filler rod. if I add rod, I kinda get a thick "blob" bead that looks funny. If I minimize heat input to keep the corner sharp, I dont get full fusion.

    Thanks.
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  2. #2
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    Re: Mitered Outside Aluminum Corners

    Here's part of a reply I did to another member who was having issues with knife edges on square tube miters. Depending on how thick the alum is you are using, would determine if I'd but them tight, gap just slightly or bevel the pieces and but them tight with a small land. He was doing 1/8" steel with stick.

    Quote Originally Posted by DSW View Post
    Mitered joints will be a bit tougher because of the thin outer corners. If anything I'd either cut the miters short or cut the piece long and grind back the knife edge on the outside corner. I'd probably suggest beveling the pieces slightly vs using a gap at your level. I'd knock a 1/16" off the top edge so you get bit more penetration and but the joints tight. Me personally, I'd just gap them maybe 1/16" - 3/32" ( I'd run a few test pieces to dial in gap, heat and so on before I jumped right in).
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  3. #3
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    Re: Mitered Outside Aluminum Corners

    Thanks Doug. I took some pics. There is some paint overspray on some beads. I used the practice pieces as a stand for an aluminum address sign i needed to repair.
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  4. #4
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    Re: Mitered Outside Aluminum Corners







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  5. #5
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    Re: Mitered Outside Aluminum Corners

    after having similar result I decided to just fuse the outside corners together at lower amps (just for looks)

    if you want full strength joints go DSW's way

    you also have other issues with that weldment
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  6. #6
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    Re: Mitered Outside Aluminum Corners

    Quote Originally Posted by Donoharm View Post
    after having similar result I decided to just fuse the outside corners together at lower amps (just for looks)

    if you want full strength joints go DSW's way

    you also have other issues with that weldment
    Teach me. I know my consistency is off. I couldn't get pics of my better beads because I made a stand with them.

    The corners I fused without filler did look better, and I could stand the piece up on end, whack the corner with a hammer, and bend the tubes before the weld gave. I concentrated on getting both sides of the joint to melt and make sure they were fused. I know that the beads ain't that purty.
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  7. #7
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    Re: Mitered Outside Aluminum Corners

    Alum joints without filler are weaker than joints with filler. In general it's best to use filler all the time with alum because you loose strength when you heat the alum at the weld. That makes the joint the weakest link. By adding filler you increase the strength of the weld to better match the unheated alum and avoid bead cracking issues that often occur when you do welds without filler on alum. Strength issues may not matter with a sign, but it's a bad habit to get into.

    Your welds look cold for the most part. An idea what thickness the material was and your settings would help. Alum needs to be welded hot and fast. You can't sit there and wait for alum to heat up like you can with steel. You need to get the puddle going fast and run with it backing down the heat as the material sucks up the heat and warms up. Outside corners and but joints are the last two joints usually a student at the tech school works on in that order. They are usually the hardest to master compared to lap and filet joints. Small runs are also hard to do because you have to stop almost as soon as you start and usually don't have time to get in the swing of things.

    I can't remember where you are on learning tig right now. Alum takes a lot more skill in heat control than steel. You have to do everything 10 times faster. If you are struggling with steel and heat control, you will have issues with alum. If you've got steel down perfect, then alum is simply learning to do everything faster.
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  8. #8
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    Re: Mitered Outside Aluminum Corners

    TA 185 with a 1/16 ceriated, gas lens with 15 cfh Ar.

    Hot start set at 30 amps over baseline, 70 amp max, 80% EN at 100 Hz.

    Tubing is .060 wall by 1". Pics greatly magnified.

    I turned the amps up to 90 at times so I could get a bead going fast, back off the pedal as I see the bead widening as I go.
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  9. #9
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    Re: Mitered Outside Aluminum Corners

    I do as DSW shows in his sketches. The chamfer is the way I like to do this. The gap method works too but it is more difficult to keep the assembly square. 1/16 material needs to be really clean on both sides (inside and outside) or you will get inconsistant results. I do a lot fo aluminum fuel tanks for racers and streetrods. I use .060 quite a bit and chamfer everything I can. I also purge tanks and charge for this. Maybe not really necessary but the inside weld looks better.

    Also if you are welding tubes don't forget to add vent holes.

  10. #10
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    Re: Mitered Outside Aluminum Corners

    I will never understand why people insist on trying to weld aluminum before they've learned the basics of tig welding on steel.

    Torch angle, heat control, consistency, arc length are all better developed on mild steel before one moves to aluminum.

    Nothing against the OP because he's new to tig, but I have yet to see a consistent bead with proper heat control, filler manupulation, crater control, consistency, in a bead on flat material or butt weld and now he's concerned about an edge on angle.

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