Chapter 3 Welding Joints, Positions, and Symbols 47 Edge preparation refers to how the edges of the joint are shaped prior to welding. If the base metal is thin, the edges may just be squared without addi- tional machining or cutting. The edges of thin metal may also be bent to form fl are-groove or edge-fl ange joints, as shown in Figure 3-2. Generally, when base metal over 3/16″ (4.8mm) thick is used, edges are beveled by machining or fl ame cutting. Edge preparation is required to allow the weld to penetrate to the required depth. Thick base metal may be machined, gouged, or fl ame cut along the upper or lower edges of the joint, or both, to form a double-bevel, V-, J-, or U-groove. A butt joint can be prepared using any of the edge preparations shown in Figure 3-2. A groove weld is made by fusing molten fi ller metal into a butt joint that has been set up in a groove formation. These groove formations include a single-square groove a single or double-bevel, V-, J-, or U-groove or a fl ared groove, which forms a groove where the edge is bent. A welder should know the names of the various parts of a groove joint, as shown in Figure 3-3A. The groove face is the surface formed on the edge of the base metal after it has been machined or fl ame cut. The total angle formed between the groove face on one piece and the groove face on the other piece is the groove angle. The bevel angle is the angle between the bevel of the joint and a plane perpendicular to the surface of the base material. The weld root is the point where the weld intersects the base metal surface near the bottom of the joint. The distance from the weld root to the point where the bevel angle begins is the root face. The root opening is the distance between the two pieces at the root of the weld. Figure 3-3B shows a cross section of a completed weld. The weld face is the outer surface of the weld Figure 3-2. Students should become familiar with the various methods of preparing the edges of a butt joint. Double grooves are used on thick metal that is welded from both sides. The base metal is bent to form the bottom three joints. Single-square-groove weld Single-V-groove Double-J-groove Flare-bevel-groove Flare-V-groove weld Edge weld on a flanged butt joint Double-U-groove Single-U-groove Single-J-groove Double-V-groove Single-bevel-groove Double-bevel-groove Figure 3-3. Approved terms used to describe the parts of a groove-type butt joint. A—The groove angle should be just large enough to allow the torch or electrode to reach the root opening. B—Terms used to describe a completed groove weld. Electrode Groove angle Bevel angle Root face Weld root Root opening Face reinforcement Root reinforcement Weld face Weld toe Weld toe A B Groove face Joint penetration or weld size