Proper Edge Preparation for T-Joint Rectangular tube ?

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Question: Say you have two rectangular tubes meeting in a T juntion. Both are 1/4" wall steel. What is the proper way to prep these for welding with TIG? I had considered beveling the leg of the T at the join meeting the top of the t. I thought about beveling 45degrees on all sides to knife edge (no land) and then leaving a 1/8th inch gap. Wrong? If so can anyone enlighten me on something better ? Thanks.Miller Syncrowave 200 Runner (Home)Victor Journeyman Torch Rig (Home)Jet Horizontal and Vertical BandsawMiller Spectrum 375 (Next on the List)
Reply:Hey kraythe,Personally, for that kind of joint, I would simply just bevel a 45* only 1/2 the thickness(.125) of your material. Why remove more material than is necessary for a solid joint? Your weld bead/heat/penetration determines strength.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:I think if you bevel that, you will have trouble getting the torch and metal in there. What is the application of this? I would just weld it up. If the application requires great structural integrity then you may need more passes to achieve the desired weld reinforcement. You will have trouble keeping the tube from bowing at the intersection, especially if you leave a gap. If you use 6010, your wont bow it so much.Good luck
Reply:Originally Posted by yorkiepapHey kraythe,Personally, for that kind of joint, I would simply just bevel a 45* only 1/2 the thickness(.125) of your material. Why remove more material than is necessary for a solid joint? Your weld bead/heat/penetration determines strength.Denny
Reply:Regardless of process, I don't see the need for a bevel inside corners. If you were welding two pieces together end to end, then you need to bevel. Just make sure your pieces are clean, since your using TIG."SOUTHPAW" A wise person learns from another persons mistakes;A smart person learns from their own mistakes;But, a stupid person.............never learns.
Reply:Here's an article a guy could look at for some additional input on what to do when. This article is looking at things from a cost perspective while obtaining adequate strength, you or I wouldn't necessarily have to give any weight to the costs only the strength values involved. I don't pay myself a wage so prep times and filler lbs aren't something I have to be real concerned with. So in this case you could look at this from the "is the extra work worth the extra strength" viewpoint. For me it is. I tend to use extra effort to make up for my lack of skills. Anyway not any one article gives you everything you need to know but they all start to come together eventually.  http://weldingdesign.com/blodgett/wdf_78335/
Reply:I stand corrected. Thanks Sandy , never knew it made that much strength difference.
Reply:Originally Posted by SandyHere's an article a guy could look at for some additional input on what to do when. This article is looking at things from a cost perspective while obtaining adequate strength, you or I wouldn't necessarily have to give any weight to the costs only the strength values involved. I don't pay myself a wage so prep times and filler lbs aren't something I have to be real concerned with. So in this case you could look at this from the "is the extra work worth the extra strength" viewpoint. For me it is. I tend to use extra effort to make up for my lack of skills. Anyway not any one article gives you everything you need to know but they all start to come together eventually.  http://weldingdesign.com/blodgett/wdf_78335/
Reply:OK reading aorund a bit more I read that AWS prefers CJP because the weld develops the same strength as the materials. So who is right? The Lincoln guy or AWS?Miller Syncrowave 200 Runner (Home)Victor Journeyman Torch Rig (Home)Jet Horizontal and Vertical BandsawMiller Spectrum 375 (Next on the List)
Reply:determine your application, then decide how to weld it. If you dont need it to hold three hundred thousand pounds, then assemble it accordingly. If you over engineer this thing, you may end up with something warped and un-usable.
Reply:Originally Posted by kraytheHmm that is an idea, would make fit up a bit easier as it would be a tad easier to clamp if there is a flat solid surface on the T. I heard from another welder, I don't remember where, that knife edge bevels were preferred for TIG and lands were preferred for MIG / Stick. It may not be true but I heard it or perhaps read in a fabrication book. The weld must be structurally strong. Its going to be holding a few hundred to a couple thousand pounds of weight in shear stress. I would worry about incomplete penetration in the weld if I did that. I have a small cup that I can use to get pretty close and the arc will be fine at that distance I think. If I couldnt get the tig torch in I could maybe stick weld it (dont like mig) but Id rather not as stick is more messy and offers less control. I am pretty certian I could get it with one tack weld pass and another fill in pass. Syncrowave can do 1/4 pretty easily.
Reply:If you are welding a t joint with rect. tubing I wouldn't waste time beveling and gapping the tubing.  I would think that if you gap the tubing it would make it harder for fitting and have your work be accurate.Also if you think about two sides of the tubing would already allow you to obtain cjp.
Reply:Originally Posted by Jay OIf you are welding a t joint with rect. tubing I wouldn't waste time beveling and gapping the tubing.  I would think that if you gap the tubing it would make it harder for fitting and have your work be accurate.Also if you think about two sides of the tubing would already allow you to obtain cjp.
Reply:What are building? Why can't you use gussets?
Reply:Originally Posted by Jay OWhat are building? Why can't you use gussets?
Reply:The table you mention is a perfect example of the problem with mig.  Easy to learn but harder to master then what most people think and that is why I like to stick.  The last part confused me about your tension/compression/shear?  because I my self would be welding all 4 side of the t joint.  In welding all 4 sides using your example 3 welds would be in tension and 1 in compression.
Reply:Originally Posted by Jay OThe table you mention is a perfect example of the problem with mig.  Easy to learn but harder to master then what most people think and that is why I like to stick.  The last part confused me about your tension/compression/shear?  because I my self would be welding all 4 side of the t joint.  In welding all 4 sides using your example 3 welds would be in tension and 1 in compression.
Reply:The welds on opposite sides of the tube DO support each other.  They do so by not allowing movement.My name's not Jim....
Reply:Originally Posted by BoostinjdmThe welds on opposite sides of the tube DO support each other.  They do so by not allowing movement.
Reply:Originally Posted by kraytheInteresting. How dows that work when trying to bend the T? If there wasnt a weld on the right side of the T and we push it to the right, the left weld will bne under tension but I dont see how the lask of right weld would matter.
Reply:I think you guys are waaaayyyy over thinking this ****.  When any two members are welded and one is allowed to move independent of the other, the weld will fatigue and break.  Welding opposite or all sides cures this problem.My name's not Jim....
Reply:I found the pict. Take a look at what happens in figure (e). Even though there is only a force (arrow shown) in one location, it affects the whole frame. The same sorts of things happen when you weld both sides of the tube.All these examples are of welded joints. There would not be as much transfer of forces if the joints had been bolted. The triangles on the left side examples show where the forces are the strongest and which way they are trying to go. In (a) the columns have a lot of side force at the tops because the beam is trying to push down. The arc at the top of (a) shows that while the force is pushing down, only the middle of the beam (the part where the arc curves above the line) is bending down. The ends where the arc goes below the line, is actually trying to bend UP. (the graphics reverse the way things look in reality. Attached ImagesLast edited by DSW; 01-16-2010 at 06:18 AM..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Ya lost me DSW.  I don't know about you, but I want a force to affect the whole frame.  That way the whole frame can resist the force.My name's not Jim....
Reply:Originally Posted by BoostinjdmI think you guys are waaaayyyy over thinking this ****.  When any two members are welded and one is allowed to move independent of the other, the weld will fatigue and break.  Welding opposite or all sides cures this problem.
Reply:Originally Posted by DSWThe key words here are "allowed to move". Welded connections done properly, even if only done on one side, should not allow movement. Joints that require movement are done with bolts to prevent fatigue.Originally Posted by kraytheQuestion: Say you have two rectangular tubes meeting in a T juntion. Both are 1/4" wall steel. What is the proper way to prep these for welding with TIG? I had considered beveling the leg of the T at the join meeting the top of the t. I thought about beveling 45degrees on all sides to knife edge (no land) and then leaving a 1/8th inch gap. Wrong? If so can anyone enlighten me on something better ? Thanks.
Reply:i remember a thread not too long ago, i think it was farmersamm, showing the fitup  on the welds going across the tube were beveled, and the joints parallell to the tube werent beveled because the radius of the other tubes corners provided the gap...
Reply:Originally Posted by BoostinjdmYa lost me DSW.  I don't know about you, but I want a force to affect the whole frame.  That way the whole frame can resist the force.
Reply:Originally Posted by DSWI agree with you.Boostinjdm. It just looks like we were going back and forth this morning, when we were both typing at the same time, not necessarily in response to what the other was typing. There are a lot of other forces in play than many think. Given a choice, on a double wall material I would weld both the left and right side of the material.
Reply:It is great to have info from AWS and Lincoln but you must realize that cost was not a factor in the info.  When you go out into the welding world cost is a big factor.  If you spend your time prepping all your joints for either CJP or PJP and its not on prints, don't be suprised at the out come.
Reply:Originally Posted by kraytheI had always planned to weld both sides of the tube anyway but this has been a fascenating discussion. Even though the topic has gotten off topic it has been interesting. Still the original question remains with two competing and both pretty well documented answers. AWS seems to prefer CJP and the Lincoln guy made a pretty convincing case for PJP.
Reply:Originally Posted by Jay OIt is great to have info from AWS and Lincoln but you must realize that cost was not a factor in the info.  When you go out into the welding world cost is a big factor.  If you spend your time prepping all your joints for either CJP or PJP and its not on prints, don't be suprised at the out come.
Reply:Originally Posted by SandySounds like you've been reading lincolns "Procedure" book.
Reply:If you used a stick welder, or a good powerful wire welder, you wouldn't have to bevel a thing.I've been told that TIG will do just fine on this kind of a joint, it puts out quite a bit of heat, but I don't do TIG so it's not for me to comment.If your bead, ie. toes-height-throat etc. is sufficient to build an amount of metal equal to the tubing wall thickness..........why worry.As long as you have sufficient penetration in the root and toes, it should work just fine.(and I've done welds before with low penetration rod that did not penetrate the root too well, but they're still holding fine)  Dunno where it's written you have to have a full penetration weld on a fillet?  Sure, you could do it, but unless it's spec'd, why worry?  The throat of the weld bead will probably be thick enough to provide adequate strength.Shoot, the filler metal your using is probably twice the strength of the parent metal anyway.If you're really stressed, and I can understand it, been there a few times, do a multi pass built up weld.If it were a piece of 1" plate, then maybe you'd have to bevel to reach the middle of the profile to give adequate strength, but it's only 1/4 wall tubing.I confess I didn't read the whole thread, but this seems silly.  I have done the same thing to myself countless times.  Think it to death.  And I'm not saying it's a bad thing.  At least you're worried, and that's a good sign.  It's the idiot that goes ahead without thinking that has trouble"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by kraytheNo jsut the article linked earlier in the thread. I would be interested to know what procedure book you mean. You have a title and perhaps an ISBN? I would be interested to know some empirical testing on identical joints welded with the different techniques and see how easy they fail in shear and tension. That would be really interesting. I suppose PJP might be sufficient for what I am doing. I would just rather over engineer than under engineer.