Plug and Slot Welds and Sizing

A plug or slot weld is used quite often in arc welding. These types of welds may only be applied in lap joints, so they are not as common as groove or fillet welds. A plug weld is a weld made through a hole in one of two overlapping parts, joining them together. A slot weld is the same concept, only with the hole being elongated increasing the area where the two parts are fused.

Many terms from groove and fillet welds are still applicable here, penetration, weld toes, and weld face. There are two new dimensions that are used to define the size of a plug weld, the plug diameter and depth of filling. The plug diameter is simply the diameter of the hole in which the weld is deposited. Though in some cases the edges of the hole may be cut at a bevel, this can improve access the the joint root in deep holes, this included angle is called the countersink angle, in these cases the plug diameter is measured at the joint root. The depth of filling is the depth, within the hole, to which weld metal is deposited. If a depth of filling is not specified the plug should be filled at least flush. In the case of a slot weld, both the width (synonymous with the diameter of a plug weld) and length of the slot, as well as the depth of filling, make up the weld size.

Attributions

1. Figure 15.14: Plug Weld by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0