Forgive the ignorant question here, but pretty new to this.
I’m TIG welding up some frames from some 1x1 tubing on my Dragon Wagon. The tops of the welds are obviously super easy to access. But I’m having some trouble accessing corner joints (both inside and outside). Most of the videos out there are MIG, and seem to be able pretty much fully weld the length corner. But I just can’t seem to do the same without fear of the arc hitting the table.
Of course I can prop the whole project up on shims…but then it seems to almost defeat the purpose of the table by only having a handful of small points in contact. How you all doing this with TIG - am I just scared for no reason?
And yes, the application would be a better fit for MIG, but the only machine I have is TIG.
Jason talks about raising the work up off the table in a couple of his videos. It doesn’t defeat the purpose. I like to use these underneath the standard fence blocks to create a built-in offset “shelf” that raises it up 1" off the table. Or you can do a full size fence block if you want it higher. If you don’t have all those, the fireball shims (or any machined shims) work just as well. You just need to have it arranged such that each contact point is either fully supported or supported on both sides to the desired height, and have enough of them spaced out to make sure the piece is stable and where you need to clamp with downward force.
Wherever there’s a choice to do things one way or another, there are consequences for each option. And we often choose one of the options to make use of those consequences themselves. Welding in a certain direction to make parts pull favourably, etc.. Putting tubing up on shims has some consequences that make it something you might actually want to do. But obviously i don’t know your exact build / requirements.
Tube isn’t a dimensionally perfect material. So if we lay it on a perfectly flat plane (table) it’s going to cause inaccuracies or difficulties. Think of the extreme and imagine fixturing a banana on a table. Where the ends end up will depend hugely on how you deal with it (clamp it). If you clamp in the middle, both ends might be up off the table. If you clamp one end, the other will be even more out-of-plane. Setting a banana up on shims is a way to (has the consequence of allowing you to choose to) have the banana reference only a few points. Then you can make fabricator’s choices by choosing where and how you shim. Like what matters more to you - the coordinates of the ends, or the coordinates of the middles of the tubes. Re-positioning shims to attain that. Forcing parts into position and welding them there, with that tension locked in the weldment, or not. That kind of thing. The plane of the table still existing as reference from which to make these choices. So you haven’t really lost anything. And you’ve gained options. Still including the option of the one special case of table fixturing, being everything locked down tight directly to the plane of the table in all possible contact points.
I like the idea of using the 1" fixtures like Jason uses in some of his videos as spacer blocks but I’m cheap. I had some 1" solid CR square bar left over from a fireplace grate build so I cut a bunch into 4" pieces. They’re all the same and the same size as the Fireball blocks if I need to use them also. Sometimes I wonder if I should have bought some 1/2" bar instead as I don’t know if I need the full 1" space, but it works for me right now.
Anyone else have any suggestions for the perfect thickness to shim the projects off the table for welding?
1/2 is the sweet spot. Just enough room to slip a sacrificial piece of material under to collect any spatter, and weld to the lowest intersection of the two pieces of material.
It makes an INCREDIBLE difference whether you alter the shape of ANY of your components by clamping. Ideally ALL the components will just simply FIT without any clamps doing anything but LOCATING the parts in relation to each other. If you need to clamp “to make the joints line up” your individual parts are not dimensionally correct.
There is also the detail of “freezing” the parts’ locations with respect to each other by tacking them; a tiny mass of solidifying metal is less likely (or has a smaller tendency) to “pull” one part relative to another.
The “stack of dimes” may be prettier without four corner tacks setting the weld geometry but which is more important (dimensional integrity or appearance) to you right now on this particular project?
If every joint can be frozen prior to releasing the LOCATING clamps holding parts to the (FLAT!!!) fixture table you’ll have a dimensionally correct weldment that will have little tendency to change shape during the subsequent full welding process. (The initial tacking is sometimes referred to as a “GeoSet” process while the structural welding is referred to as “Weld”).
I would also heartilly recommend the videos Jason put up about “Weld Distortion” in which really serious heat soak around welds is examined.