Interesting position.

My take would be as follows:

The dihedral angle of an edge joint must be 30 degrees or less. The edge weld depicted is used to "fuse" the edge joint, but if you look at the flanged edge, it forms an edge joint in that the two members meet tangent to each other and the dihedral angle between them is zero degrees.

Using your sketch of the flanged joint; if you move one of the two members in either direction, but still keep the faying surfaces in direct contact you end up with a short lap joint and the weld would be a fillet weld because it would be deposited on the joint rather than in the joint as depicted by the various groove details in the same series of sketches.

I agree that had the original weld detail described by the inquiry been slightly offset, the designer could have used either a fillet weld or a groove detail to make the weld. The groove detail (other than a "seal weld" along the edge) would require some type of joint preparation, a V, J, U, or bevel, to deposit the weld "in the joint" rather than on the joint as is the case with a fillet weld.

The sketch attached shows just two of the options that could have been used and differentiates between the fillet weld (on the joint) versus the groove (in the joint).

Best regards - Al

Melt thru is defined as visible root reinforcement produced in a joint welded from one side.  Reinforcement is defined as weld metal in excess of the quantity required to fill a joint.  The initial post states that "the weld takes place from the outside with complete penetration".  In my opinion, melt thru is not the same thing as complete penetration.  If the joint is to be complete penetration, it must be welded from one side, backgouged to sound weld metal from the other side and the other side is welded, or, the joint is welded from one side using a suitable backing material.  If the joint is backgouged, it's good to get "melt thru", because that side of the joint doesn't have to be backgouged as deep to get to sound weld metal. 
There's obviously going to be some melt thru when plates are only in contact with each other along their edges.  Since this is not a "conventional joint", and I say that only because the joint configuration is not one that's shown in A2.4, I don't see why the symbol couldn't show a fillet weld on one side of the weld symbol reference line and a melt thru symbol and dimension on the other side of the weld symbol reference line, if melt thru is the only intention.  But, since the poster stated that "the weld takes place from the outside with complete penetration"..... as the joint is now, there is a 90 degree groove opening to fill that must be either backed or backgouged and welded from the other side.  From a D1.1 standpoint, this type of joint would require a PQR, as it is not prequalified. 

Hello Jeff;

Your decision to join the ranks of our "trade" will serve you well over your working lifetime if you continue to learn and prefect your skills. All too many people reach a plateau early in life and stop listening to new ideas and stop expanding their skill sets only to become stagnated in their careers.

I learn something new everyday and much of the knowledge is from the shared ideas with gentlemen like Lawrence, Scott, Gerald, John, Stephan, Chet, Henry, Allen, and too many others to list here.

In trying to answer an inquiry I tried to go back to the "basics" and attempt to substantiate my position with some "research", i.e., review my A3.0 for standard terms and definitions as well as A2.4 for standard welding symbols. I also use a few sketches to help explain the position I take when they help to clarify the issue. I take into consideration what other folks have to say on the subject and try to keep an open mind, because the good Lord knows I'm wrong as often as I'm right.

You've been a member of the community (the Forum) for a while now, i.e., this isn't the first time you've asked a question or jumped in with your opinion. Many of the inquiries lead to some lively conversations because nonstandard terminology leads to misunderstandings or misinterpretations of actual inquiry. I despise the use of nonstandard terminology because of the confusion it creates. This is one of those cases where the welding symbol is in question because we are in disagreement as to the type of weld being deposited. Is the weld a fillet weld or is it a groove weld?

You take the position it is a groove weld, but you haven't supported your position based on a reference source. I assume that your instructor told you that it was a groove weld because it is an outside corner joint, thus it has to be true. I can only urge you to go back to your text books and other references published by AWS (as an example) to substantiate your position (take note of Lawrence's reply where he lists his sources and he even included a sketch taken from the reference source). You will notice that the gentlemen that are regular participants in the forum that I hold in high esteem general include a reference to a recognized code, standard, or text book. This lends credibility to their response and the opinions they express.

So, I challenge you to support your position that the weld described is a groove weld based on some authoritative source. I'm not making this challenge in an attempt to "bully" you into agreeing with my position. I'm challenging you to force you to use the resources available to you and as a means to extend your understanding of the technical aspects of welding. This is how we all further our knowledge. I would hate to tell you how many times I've "deleted" my initial response after going back to the "books" only to learn that my initial position was incorrect. However, in doing so, I am forced to "learn" and rethink my position on the subject.

How do you differentiate between a fillet weld and a groove weld? That is the basis of this inquiry. Good luck and good reading in researching this questions. I look forward to your response. Show me where my thought process has lead me to a wrong conclusion (it will not be the first time I've been shown that I'm wrong). I know you're up to the challenge. :)

Best regards - Al