# Deciphering Weld Symbols, Part 2: Groove Welds

September 30, 2020

We review common welding symbols and their meaning, with the focus in this article on groove welds. Part 1, presented in the August issue of MetalForming, covered welding-symbol structure and provided an overview of symbols for fillet welds as well as for plug and slot welds. Welders commonly perform groove welds to make edge-to-edge joints, although groove welds also are used for corner joints, T joints and joints between curved and flat pieces. The variety of groove-weld symbols (Fig. 1) suggests many ways to make a groove weld, the differences depending primarily on the geometry of the parts to be joined and the preparation of their edges. Performing a groove weld consists of depositing weld metal within the groove, where it penetrates and fuses with the base metal to form the joint. (The drawings in this article generally do not show the penetration of the weld metal. Note its importance, however, as the degree of penetration is crucial in determining weld quality.)

Square Groove

In a square-groove weld, the groove is created by either a tight fit or a slight separation of the edges. The weld symbol indicates the amount of separation (Fig. 2).

V Groove

With V-groove welds, the edges of both pieces are chamfered, either singly or doubly, to create the groove. The weld symbol provides the angle of the V, as well as the separation at the root, if any (Fig. 3). If the depth of the V does not reach the full thickness of the workpiece, or half the thickness in the case of a double V, the depth is noted to the left of the weld symbol. Should weld penetration be greater than the depth of the groove, the depth of the effective throat is provided in parentheses after the depth of the V (Fig. 4).

Bevel Groove

When performing a bevel-groove weld, the edge of one of the workpieces is chamfered, with the other left square. The bevel symbol's perpendicular line always is drawn on the left side, regardless of weld orientation. The arrow points toward the piece that is to be chamfered, emphasized by a break in the arrow line (Fig. 5). The break is not necessary if the designer has no preference as to which piece receives the edge treatment or if the piece to receive the treatment should be obvious to a qualified welder. Angle and depth of edge treatment, effective throat and separation at the root are described using the methods discussed in the V-groove section.

U Groove

When performing a U-groove weld (Fig. 6), the edges of both pieces are given a concave treatment. Depth of edge treatment, effective throat and separation at the root are described using the methods discussed in the V-groove section.

J Groove

The edge of one of the pieces in a J-groove weld receives a concave treatment while the other is left square. The J-groove weld is to the U-groove weld as the bevel groove weld is to the V-groove weld. As with the bevel, the perpendicular line in the symbol for a J-groove weld (Fig. 7) always is drawn on the left side, and the arrow (with a break, if necessary) points to the piece that receives the edge treatment. Depth of edge treatment, effective throat and separation at the root are described using the methods discussed in the V-groove section.

Flare-V Groove

The flare-V-groove weld commonly finds use when joining two rounded or curved parts. The intended depth of the weld itself is given to the left of the symbol, with the weld depth shown in parentheses (Fig. 8).

Flare-Bevel Groove

Welders typically employ a flare-bevel-groove weld when joining a round or curved piece to a flat piece. As with the flare-V-groove weld, the depth of the groove formed by the two curved surfaces and the intended depth of the weld itself reside to the left of the symbol, with the weld depth shown in parentheses (Fig. 9). The symbol's perpendicular line always is drawn on the left side, regardless of the orientation of the weld itself.

Melt-Through and Backing-Bar Symbols

Common supplementary symbols used with groove welds include the melt-through and backing-bar symbols. Both indicate the use of a single-sided groove weld for complete joint penetration. In the case of melt-through (Fig. 10), the root is to be reinforced with weld metal on the back side of the joint. The height of the reinforcement, if critical, is indicated to the left of the melt-through symbol, placed across the reference line from the basic weld symbol. When employing a backing bar its symbol locates across the reference line from the basic weld symbol (Fig. 11). If the bar is to be removed after welding, an "R" is placed within the backing-bar symbol. The backing-bar symbol has the same shape as the plug- or slot-weld symbol, but context should make the symbol's intention clear. MF

This article is an excerpt from an online presentation provided by Miller Electric Mfg. LLC, Appleton, WI; www.millerwelds.com

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