You may know what welding is, but do you know what groove welding is and how to read the symbols?
Groove welding is a specific way to attach two pieces together, or create a joint. As there are many types of groove welds, each one needs its own specific symbol. The symbol gives all the information you need to create a correct and accurate weld.
This article will start by discussing welding joints and symbols as a whole. Then, we’ll go into more detail about groove welding and joints. After that, we’ll discuss how to understand and interpret the specific groove weld symbols. In short, you will definitely leave this article with much more knowledge about groove welds than before! So, let’s get into the groove!
The Scoop on Welding Joints
Before we discuss groove welding, let’s get a little better idea of what welding joints is and how it’s done.
The definition of a welding joint is an edge or point where two (or more) pieces of either plastic or metal are joined together. Those pieces of plastic or metal are commonly known as “workpieces.” The workpieces are welded together based on a particular goal or geometry individual to each project design. There are actually five types, according to the American Welding Society (AWS). We’ll go over them briefly before getting into the really good stuff.
- Butt joints: Two workpieces are joined in the same plane. Most groove welds occur on butt joints. There are multiple subcategories of butt joints, which we’ll discuss in a bit.
- Corner joints: Welding done on the outside edge of the (usually metal) workpiece. It will always come together at a right angle and forms an L. Another type of groove weld.
- Edge joints: Workpieces are welded on the same edge, set side by side. Usually in a location where adjacent pieces need to be attached, and with flanging (rim) edges. Another type of groove weld.
- Lap joints: Welding that joins two overlapping workpieces that have different thicknesses. A type of fillet weld.
- Tee joints: Two workpieces (usually metal) that are welded together perpendicularly. Another type of fillet weld.
Ok, So What is Groove Welding?
Officially, a groove weld is a type of weld that fills the gap and connects two pieces. As we briefly looked at, groove welds can be done on the surface of a workpiece, between the surfaces of two workpieces, between the edges of two workpieces, or between the surfaces and edges of two workpieces.
Here’s the confusing part… the weld groove is actually the channel and not the whole weld! The channel is created either on the workpiece’s surface or as an opening between joint members where the weld metal goes.
The name “groove weld” comes from the way a groove initially forms between the edges of the two materials.
One other important thing to know is the difference between groove welds and fillet welds. While they do have plenty of similarities, they are not the same thing. Fillet welds involve a triangular cross-section that joins two workpieces at right angles (lap, corner, and T-joints).
Groovy? Let’s move on to specific categories.
Categories of Groove Welds: Single/Double and Complete/Partial
It should be noted before we move on that there are also two different categories of groove welds – single or double and complete (CJP) or partial (PJP) joint penetration.
- Single vs. Double: Single groove welds are only on one side of the joint. They are known just by their name (bevel, v-groove, etc). Double groove welds are on both, and usually have double in their name (double bevel, double v-groove, etc).
- CJP vs. PJP : With a CJP weld, the gap fills completely between the two workpieces. All single groove welds are CJP unless noted. In contrast, a PJP weld has only a partially filled in gap. Unfortunately, CJP welds are also the most expensive.
As we initially talked about, when looking at a design plan for a weld, symbols are present in place of written directions. It is imperative that anyone welding understands how to read weld symbols. We’ll start with the basics.
The General Structure of Weld Symbols
Basically, in both fabrication and engineering drawings, most welders and designers use specific shorthand weld symbols. These symbols describe a variety of information about the weld – type, size, processing, and finishing details.
The symbols themselves come from the ANSI (American National Standards Institute) and the AWS (American Welding Society). They are used universally, so it is important to memorize them or at least have a copy to reference.
Each symbol’s structure starts with a horizontal line, called the reference line. It functions as an anchor for the other welding symbols that attach to either end. The designer puts specific instructions for the weld on either side of the reference line (above or below).
At the end of the reference line is an arrow. The arrow connects it to which joint needs welded. In addition, it can go either up and to the right, down and to the left, or a variety of other combinations.
Each and every welding position has its own symbol, which is basic in nature. The weld symbol is on the reference line, usually right in the center. It is a tiny drawing that looks like a cross-section of the joint weld, only more simple.
So we have lines, arrows, and symbols. How the heck do you read and interpret all of that?
Steps to Read Groove Weld Symbols
- Determine joint type and preparation. This will include either single or double and the type of groove weld (discussed below). For that, look for a jog or break in the arrow. If there is one, it will point to the side that needs to be prepared. If it’s straight, it will be a double groove weld.
- Determine root opening. This is inside the symbol that shows the groove weld type. If there no dimension is shown or if there is a “0”, no gap should be between the pieces. The root opening should be predetermined.
- Determine root radii and root face dimensions (only for U-Groove and J-Groove welds). Shown one of two ways – a drawing of a cross-section showing the dimensions or notes drawn on the tail to reference another document. Root face is sometimes called “land.”
- Determine groove angle. Shown either above or below the root dimension, shown in degrees.
- Determine groove depth. Shown on the left side of the symbol. It includes the whole groove.
- Determine weld size. Includes the groove depth and any additional root penetration. It is shown on the left of the symbol and is written in parentheses (PJP). If no number is shown, the weld size should not be any less than the groove depth (CJP).
- Determine finish contour. There are three options – flat/flush, convex, and concave. Each has its own symbol.
- Determine finishing method. Watch for the following specific letters.
- Chipping (C)
- Grinding (G)
- Hammering (H)
- Machining (M)
- Planishing (P)
- Rolling (R)
- Unspecified (U)
So, as you can see, the welding symbol gives us everything we need to know before we perform the weld. However, each groove weld has its own unique symbol to look out for as well!
Specific Groove Weld Symbols And What To Watch For
- Square Groove Weld: A butt-welding groove joint. Two pieces are parallel to each other and flat. The symbol is the reference line with two perpendicular lines.
- V- and Double V-Groove Weld: A single or double butt weld with beveled edges on both sides. The symbol is the reference line with a V.
- Flare-V Groove Weld: A single butt weld that joins two curved or round pieces together. The symbol is the reference line with a perpendicular line and a curved line that begin at the same place.
- Bevel and Double Bevel Groove Welds: A single or double butt weld with either one or both beveled edges. The symbol is the reference line with an angled V on top for bevel and one on top and bottom for double bevel (K).
- Flare Bevel Groove Weld: A single butt weld that joins a curved or round piece to a flat piece. The symbol is the reference line with a perpendicular line and a curved line that begin close to each other. The perpendicular line is always on the left, regardless of the weld’s orientation.
- J- and Double-J Groove Weld: A single butt weld where one edge looks like a J and the other piece is square. The symbol is the reference line with a perpendicular line and a curved line on top to either the right or the left.
- U- and Double-U Groove Weld: A single or double butt weld where both edges look like a U (or are concave) or two U’s. The symbol is the reference line with a perpendicular line and two curved lines on top (Y) for the U-groove. The double-U groove is the same, but with a second Y on the bottom.
Supplementary Groove Weld Symbols
In addition, there are also two common supplementary symbols that designers can add. Both show joint penetration with a single groove weld. These symbols are the backing bar and the melt-thru.
For instance, if there is a melt-thru symbol, we should use weld metal on the joint’s back side to reinforce the root. On the left is the reinforcement height, which is located across from the basic weld symbol on the reference line.
Conversely, if there is a backing bar symbol is on the reference line, a backing bar should be used for complete joint penetration. In addition, if there is an “R” inside of the symbol, the bar should be removed after welding is complete. Because this groove weld symbol is similar in shape to the slot or plug weld symbols, always look for the context.
Groove Weld Preparation
One last thing to discuss related to groove welding specifically is the proper preparation of the workpieces before starting the physical weld. The whole reason we do this is to help guarantee the strongest weld possible. Butt joints, which is where most groove welding happens, tend to require the least amount of preparation but it is still essential. Ultimately, good groove weld preparation saves welders time, money, and frustration.
Welders use five common techniques to prepare the plate edges, each with their own advantages.
- Oxyacetylene cutting (like oxy-fuel cutting and welding) – most commonly used for steel.
- Machining – used often for both J- and U-groove weld joints. Good for mass production.
- Chipping – best for casted parts.
- Grinding – good for small sections.
- Air carbon-arc cutting/gouging – most commonly used for carbon steel, cast iron, and stainless steels.
In addition, if the workpieces are not the same material, welders can use buttering. Buttering is a type of surface welding to make the workpieces more compatible. Each end is covered in a transition material, then the weld moves forward.
Never Forget Safety
Before we go, a quick reminder of basic welding safety precautions. There is always time to make sure you’re wearing the right personal protective equipment!
- ALWAYS wear an OSHA appropriate face shield to protect your eyes from burns and debris.
- Wear a non-flammable, long-sleeved shirt to protect your arms from burns.
- Use welding gloves to keep your hands safe from cuts and burns.
- Remember to wear closed-toed shoes to protect your feet from injury.
- ALWAYS use proper ear protection.
- NEVER weld around or on anything that has brake cleaner. When combined with ultraviolet (UV) light, it creates phosgene gas. It is highly toxic.
In addition, always be vigilant for potential fire or electrocution risk. While you may feel safe, especially if you’ve been welding for a long time, it is still dangerous!
Above all, groove welds are an essential part of creating butt joints. However, creating them requires the ability to read and understand weld symbols. This can seem extremely difficult if you haven’t done it before. Hopefully, you now understand the process and why it is important and are ready to get out there and weld! And remember, groove welds are “groovy”! We’ll see you next time!