For novelty sake.
I needed at least one welded edge of abutting tubes (the inside corner of a frame) to have no bead buildup. And wanted to avoid grinding away a bead from that inside corner.
Itâs not easy, with limited visibility, torch in the only line of sight, excessive tungsten stickout. But it does allow one thing that you canât often do on the outside face - massive bead buildup. Since itâll never be seen, inside the tube. Versus welding this edge from outside teh tube and then grinding away most of that weld.
. (This was obviously my worst one. All subsequent beads inside-tube were even, shiny , etc.)
And being able to do that outside corner edge inside the tube without any âpush-throughâ bead was due to the heat sink 90 deg form block up in the 90 of the frame.
There are obviously intricacies. And youâre trading lots more work and more tricky welding for that clean corner on the inside of the frame. So you wouldnât be choosing to do it this way for âfunâ. But i thought iâd share the possibility.
Was it because you needed a sharp corner for some reason? because if the corner can be rounded, discs like these seem to work well (though wonât get the sharp edge, just a radius)
Exactly. itâs about the unadulterated sharp inside corner. In my particular case, for my final product, with others and their own skill level working on it later, etc., - the prosâ of having the sharp corner established in fab / welding outweighed the prosâ of approximating it later.
Thatâs pretty cool trick, might come in handy one day. Thanks for sharing!
Does it take much longer to cut the tubes like that? And did you consider or try tig welding the joint without filler? Iâve done it with thin wall stainless, not sure if it would work with thicker steel like that. And it would be weaker than your method.
Very Clever!!! I would add though that if one is accustomed to setting the angle of this sort of weldment using fit-up of the tube ends/edges these special edges might make the angles hard to get just right. Iâd argue for fixturing the square tubes on a fixture table to keep them at 90 degrees and welding over the small resulting gaps.
Oh yes, much longer for the parts prep (cutting). I did the marking by making a little jig / form that slides over the tube and acts as a stencil to scribe against. So thereâs that make-a-tool step. Then, the cut is not in one plane so a simple sectioning machine canât be left to do it, and itâs likely a by-hand deal, though rotational laser tube cutters surely could do it.
My choice of whether to use filler or not doesnât come down to the joint type, itâs about the fixturing or fabrication approach (?style). in this case i made parts shorter than the final weldmentâs dimensions (as little shorter as possible) and built around an inner form. So there were (purposely) gaps at each joint. That needs filler.
Exactly right. Nice to see this kind of intuitive understanding of whatâs actually going on in the fabrication process, vs just a bunch of rules to follow to make a weldment come out right.
âBuilt them around an inner formâ OK GD&T people, that fabrication method corresponds to specifying the size of the weldment by an inside dimension. If an outside dimension is specified and then the parts are fixtured around an inner form you are taking a first step into the woods. Itâs not âillegalâ or even contrary to ASME Y 14.5 but it may be a foolâs choice.
Very true. One can tell when working this way that the frame contracts around the form. So getting it out needs a plan behind it itself. (Maybe a âcolapsingâ form; maybe something that has some give and can be hammered out; etc.) Fitting right with the schema of having a strong concept of the process before embarking on it. In my case, making the form(s) the expected amount larger so that it shrinks into size. But that also wasnât so important in this case of bedside table frames.
Side thoughts on building around a form - It has been super useful to me since i donât have all the tooling iâd like and a fab table. Itâs an approach that we donât hear spoken about much in places where a proper set of fab tooling is the aspiration. But it is almost a whole nother philosophical approach. Specific negatives (for the project) which you build around. One of the values of having a set of fab tooling is not having to question philosophical approach, since you can do almost anything and the âwayâ is obvious following the tooling in front of you. But for someone without that tooling, remember that there are other entire approaches to building from metal in 3D. Kinda like there are different approaches to other things, like dimensioning (relative; absolute) for example. You have the expense of the âmouldâ. But if you can cut rectangles from particle board, youâre on your way.
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Just keeping reference to the post theme for everyone - Building around a form isnât a requirement of this joint âtypeâ.
Maybe I missed it but did this application need that joint to be welded? I thought there was something said about bedroom table frames. If they are just a table frame why not just delete that section of weld?
Thatâs a good version of the joint to keep in mind as a possibility. And would have been the smart thing to have done in my instance.
I didnât, because i wanted to try the âfullâ version. Learn what has to be done (weld order; how tricky the inside bead is to do; etc.), and the effects. And to be able to show the completely welded version. I had the time to play over year end. So i paid with time to run this experiment.
