Dealing with gap when welding square tube

[Debriefer]

Say you have a square tube, and you want to weld another to it, in a perpendicular fashion (a 'T'). Two edges will be flush, but the other two will have gaps because of the rounded corners. Depending on the size and thickness of the tubes, this may not matter, but when you have thin wall stuff especially, there is a big gap.

Is there a quick solution to producing strong welds in this case, without resorting to making what would basically be a square-ish fishmouth cut in the one piece of metal?

 

[yaidunno]

All the thin wall square tube i've worked with have had small radii on them, making the issue you speak very minor. Do you have a picture of the pieces of tube? Cutting the profile on the end like you say, is the only real way to get a zero gap fit.

 

[zkling]

Can you post a pic? Say I weld a "T" the top horizontal portion should be of the same or greater width than the vertical tube. Ex. I have a 1x1x0.095 wall tubing for the vertical portion. I really should use a 1x1x0.095 or AxYx0.095 where A is the width and greater than or equal to 1" for the top horizontal piece. I really hope that made sense. A picture would be great.

 

[AndyA]

Really only two choices. Either weld to fill the gap, or grind the open tube end to match the curved corners.

 

[exophyusical]

Gap filling 101

Concentrate your heat on the radius edge, not the cut edge, if you can adjust the position so that the radius is on top and the cut edge on the bottom you can get gravity on your side, helping the puddle run down onto the cut edge without needing to concentrate your arc on it too much. Build the puddle up on the side that will take the most heat and the draw it over to the other side in quick whips.

If you need to, build up a few passes on the radius edge, for some reason running a quick pass down the cut edge ( more or less just burning it a little) seems to help keep it from burning out.

Push your puddle, whip the electrode, if you feel it burning through just jump ahead and let that spot cool. Sometime jumping ahead and welding back into your weld in short stitches can work. If you need to fill a burn through, build the puddle on either side and then us the electrode heat to draw the metal into the hole.

If all else fails employ the "STIG" technique, smash the slag of another rod and feed it into the puddle with your free hand.

If its a **** weld grind it down a little and burn it out with another pass.

 

[BD1]

Are using stick or mig ? If mig, just lower setting to a size thickness below what you have. If stick lower amps and use a whipping motion. Put rod in puddle and back away some allowing the ''fast freeze '' of 6010 to freeze and bring it back into puddle.

 

[MillerMav]

I will also go with laying the bead on the radius instead of concentrating heat on the thin wall. I just dealt with this on my weld cart build. I was using thinner wall 2x3 tube against thicker wall 4x6. It was a learn by doing exercise for me but I did find that if I concentrated my weld on the heavier wall material and "whipped" it into the lighter material it worked quite well. It took some practice but I got it.

You can also run tack's as if you were doing body work. I have done this as well with great success. I just put a decent tack in one spot and then move over 50% and do another. I "stack the tacks" lol!

 

[Debriefer]

Here's a picture of what I am describing:

Here are some attempts I've made in the past to work with the gap. I don't remember, but I think #3 is what I have at least gotten away with: making a straight pass on the non-end piece to partially fill the gap, and then coming back and doing a herringbone/whatever you want to call it (I drew spirals, that's not really what I meant).

 

[mjb]

Took a quick pic of some 2x2 11 gauge.

 

[ZRX61]

I just look upon it as not needing to V groove the joint

 

[dragginbalz]

MJB - Man I want to just grab the welder and weld that up looking at the picture (I don't get to weld much anymore

Those are my favorite joints to weld. Those and outside corners. Easy to get a nice flat bead with very little grinding to smooth it flush....ahhhh....good times

If the tubing it too thin and you are burning though with that small gap, you can run a quick pass on the **** end tubing side to build up a little material on the edge prior to welding fully. Then burn in a second pass concentrating more heat on the radiused side and moving the puddle over the the edge of the piece that will have a tendency to burn away quicker.I would say unless it is ridiculously thin (under 16 gauge) you should be able to do that in one pass with the correct settings and technique.

 

[that-guy]

concentrate your heat onto the radiused piece and flow your puddle into the butted piece. making nice large/slow circles to both fill the gap, and get excellent penetration into both tubes...i will be doing this soon on my 2x2x.120 tube frame for my welding table

 

[MillerMav]

Looking at your picture I don't see any issue with running a single bead on the radius and whipping it into the wall of the perpendicular tube. I got a couple scraps at home. I will set this same scenario up and try it out to confirm.

 

[DesertSparky57]

Some good advice above. This is 2x2x.180, the gap is not huge on this size, but it didn't work out right the first time I did it because I aimed the electrode at the center of the gap thinking that starting the weld down deep would be the way. I have learned since that I like dragging/pulling better, I like to melt on to the radius pretty good and carry a nice puddle in slow ovals kind of. The second shot gives a side view of the same type of joint and you can see even going as slow as I did the weld stays good and flat. I love the gap actually, it's become my favorite joint style so far to weld. Others may like the traditional steady pace no wiggle pass, just set the welder right and you can do either with good results.

 

[nine4gmc]

Those are nice welds!

 

[Rezarf]

Great advice so far, I agree the radius on the tubing gives me a better weld everytime... I feel like it gives me some more "natural boundaries" to stay inside.

 

[exophyusical]

Those are nice welds!

Yep, but you need to tie your corners in a little better, carry the weld around the corner from each direction. It might not look as smooth but if you get any cracks they are going to start in those corners. Just nit picking though, those are nice welds.

Dragging the weld gets you better penetration than pushing, but for getting deeper in the V like you are describing I sometimes run a triangle pattern with mig. Burn into the bottom of the seam, then come up the radius edge, let your puddle build a little bit there if you need, then across to the **** edge, it can be important that you come out of the seam up the radius edge rather than the **** side.

Circles, patterns, magic formulas to whip your electrode in, these are all just learning tools for the most part. They develop "muscle memory", the long term goal should be to get to the point where you generally just watch your puddle and let your muscles react according to what your eyes see. IMO the most useful of these "formula methods" is the saw tooth whip, learn to do this well, break away from the mechanical repatition and simply use it to react to what your puddle is doing, and you've pretty much got any position with any of the more common methods down.

 

[exophyusical]

Great advice so far, I agree the radius on the tubing gives me a better weld everytime... I feel like it gives me some more "natural boundaries" to stay inside.

It is simply your greatest heat sink, that's one of the rudimentary rules of welding, concentrate on your greatest heat sink. Some times its to avoid blowing through, other times its to get good fusion, but its something that should always be considered.

 

[lilscorpion]

If the gap is great enough, and the material is thin enough (where you can't fill ), the right way is to fish mouth / cope. Sometimes the easy way is not the right way and other times function supersedes form. Just gotta determine which is right based on the use-case. If you want all of your welds to be says string as they can and pretty, sometimes there's extra work to get there.

 

[DesertSparky57]

Totally agree exo. I've since been really working at not stopping early on the corners. That pic actually perfectly captured the problem! The technique stuff you mentioned is spot on too. I am realizing that it's not all about always making the same exact movement. The ability to watch the puddle and what it should be doing is coming very slow for me, but I've found that if I let my movement sort of be a by-product of the joint type and how the puddle is behaving I almost always get nice results.

If I just try and force a specific puddle shape or speed.... Eh, almost always ends up cold-lapped. Couple bad technique with a small 120v machine and it is really easy to end up with a weak weld.

Once I got a feel for the settings things started looking better, now I stomp all over the duty cycle. Really really want to trade my little red 140 for an Ironman230.

 

[DekeT]

Damn, I wish I could get those kinds of welds in my shop.

 

[exophyusical]

Totally agree exo. I've since been really working at not stopping early on the corners. That pic actually perfectly captured the problem! The technique stuff you mentioned is spot on too. I am realizing that it's not all about always making the same exact movement. The ability to watch the puddle and what it should be doing is coming very slow for me, but I've found that if I let my movement sort of be a by-product of the joint type and how the puddle is behaving I almost always get nice results.

If I just try and force a specific puddle shape or speed.... Eh, almost always ends up cold-lapped. Couple bad technique with a small 120v machine and it is really easy to end up with a weak weld.

Once I got a feel for the settings things started looking better, now I stomp all over the duty cycle. Really really want to trade my little red 140 for an Ironman230.

You got that right brother! Its real important with those little machines that you keep the wire burning right into the metal, no puddle surfing at all, which means lots of electrode manipulation. I guess that's probably how "magic formula" welding gets started. They also require their own set up too, for me that usualy means maxing the heat up (or stomping all over the duty cycle as you put it) and then setting the wire to whatever the heat will manage, this is totally contradictory to how they teach you to set up a machine in welding school.

At millwright school we had a clean up day at the end and one of the instructors asked me and another guy who had a welding ticket if we could figure out how to get their little mig to work. Having run one before I set it my way, the other welder told me I was doing it all wrong, which technicaly is in fact correct. We made up some cupons and I ran a weld, and he ran a weld. His weld was horrible, all ropey with no fusion whatsoever to one of the pieces. I did the triangle thing I tried to describe to you, that way the wire itself is burning into the crack and both of your pieces as well as doing some filling overtop, it looked pretty good. We put them in the press and broke the pieces apart, then I took a chisel and knocked both of the welds completely out (it was pretty heavy plate that we were welding) I told the Instructor "Take these to your boss and tell him to get you a new welder."

 

[Ozwelder]

Say you have a square tube, and you want to weld another to it, in a perpendicular fashion (a 'T'). Two edges will be flush, but the other two will have gaps because of the rounded corners. Depending on the size and thickness of the tubes, this may not matter, but when you have thin wall stuff especially, there is a big gap.

Is there a quick solution to producing strong welds in this case, without resorting to making what would basically be a square-ish fishmouth cut in the one piece of metal?

Some people who don't have a stick machine and not a mig ,and are limited by using thinwall gal tube. We could be talking 65 thou (your 16G) wall thickness.Easy with a mig but not so with an old buzz box.

If an inverter stick machine is used, its doable by building up the adjacent radius and grinding off until a square corner there-by allowing good fitup and subsequent tack up and welding.

My 2c worth
Oz