Welding Symbols Demystified: Part Two

Judy talked to you on Wednesday about five of the most common mistakes made when reading welding symbols. You’d think that would cover it all, right? Wrong. I’m here to tell you that we have more, five more in fact. (I bear great news, don’t I?) As Judy mentioned, trying to decipher AWS 2.4 initially came to us as a feat comparable to decoding ancient Egyptian hieroglyphs. From the outside looking in, these symbols were merely circles, triangles, and rectangles idly sitting on a line that pointed to what seemed to be the letter “T”. Puzzling indeed. Slowly, and I mean slowly, these geometric shapes and th at letter “T” came to mean more, and now that we have made welding symbols more accessible, we know it will be clearer to others as well.

You’ve seen Judy’s starting lineup of mistakes; now let’s take a look at the next string.

Mistake No. 6: Weld Symbol vs. Welding Symbol

While these two words sound the same, they imply very different things. A welding symbol is the entire image as it appears on a plan. It includes information such as a reference line, an arrow, weld dimensions, notes, as well as the weld symbol. A weld symbol is a single element that is part of a welding symbol. It indicates what type of weld is to be applied to the joint. Think about it this way, a welding symbol is made up of weld symbols, but a weld symbol is not made up of welding symbols.

Mistake No. 7: Weld Process References

To indicate that a specific weld process is to be used, an abbreviation is placed within the tail of a welding symbol. For example, the abbreviation for electron beam welding is EBW and the abbreviation for gas tungsten arc welding is GTAW. So, naturally, the abbreviation for resistance spot weld is RSW, right? If this is so, then what is the abbreviation for resistance seam weld? These assumptions can land you in hot water, so if there is any confusion, always consult a list of abbreviations.

Mistake No. 8: Views of a Joint

This first image shown here is the top view of a corner joint. The second image shows the side view of a T-Joint. Notice any resemblance? That’s because these two images are exactly the same. If there is ever any doubt, look for another view of the joint on the plans or ask a supervisor in order to be absolutely certain before welding.

Mistake No. 9: Fillet Welds with Unequal Legs

These are tricky. A fillet weld with unequal legs has two separate leg sizes. This can be communicated on a welding symbol using two different methods. The first is by using dimension lines. The area that is encompassed by the dimension lines, receives the dimension indicated next to it, not the member that the dimension line touches. This can also be indicated by using a note written within the tail. Both of these indications also tell us, not only which dimension applies to a specific member, but which dimension applies to the other as well.  On a plan, only one dimension needs to be indicated in the drawing in order to assign a leg size to a particular member. As long as you know where one dimension goes, the other dimension applies to the remaining leg by default.

Mistake No. 10: Weld Symbol Doppelgänger

There are a few weld types that use the same weld symbol, such as plug and slot welds and spot and projection welds. When reading these symbols, there are a few ways to differentiate between the two. Let’s look at plug and slot welds. With plug welds, the diameter symbol is used to indicate plug weld size since plug welds are round. Slot welds, however, are elongated. They are dimensioned by width and length, a dimension which plug welds do not have. If there is a diameter symbol, then it’s a plug weld. If there is no diameter symbol, then it’s a slot weld. It’s as simple as that.

To get better acquainted with these rules or for more information, check out our latest course: Understanding Welding Symbols, scheduled for publication on March 28th. Within this course, we cover all the mistakes discussed in this blog in addition to the rules that apply to all of the other welding symbols. The course starts with very basic concepts including the five joint types and how they look on a plan, and then it walks you through the more in depth concepts such as, what to do when a fillet weld has uneven legs or how to communicate which weld process is to be used on a joint. From the outside, AWS 2.4 seems like a rather unassuming book of standards, but let me tell you, that little book packs in pounds and pounds of encrypted information within a very thin spine; information needed in order to make the big leap forward to becoming a CWI. With Understanding Welding Symbols, we help to lighten that load so that you can strut a little more confidently toward your goals.

Alicia Garcia