Chapter 3 Welding Joints, Positions, and Symbols 65 3.5.11 Plug and Slot Welds Occasionally, it is necessary to weld two pieces together at points that are not located on the edges. This is done by creating a hole in one piece and welding the two pieces together through this hole, as shown in Figure 3-37. The holes are usually round, but may be of any shape. Holes may be drilled, fl ame-cut, or machined. If the hole used is round, the weld is called a plug weld. A weld made in a hole that is not round is known as a slot weld. The weld symbol used for the plug weld is shown in Figure 3-38. The size of the plug is shown to the left of the weld symbol. In either a plug or slot weld, the sides of the hole may be coun- tersunk (slanted). If a countersink is used, its angle is indicated beyond the weld symbol, as shown in Figure 3-38. (See also location “A” in Figure 3-21.) The depth of the weld is shown inside the weld symbol. See Figure 3-38B and location “R” in Figure 3-21. A plug weld’s exact location on the weldment is shown on the assembly drawing. The length, width, angle of the countersink, and the location and spacing of the slots for a slot weld, are not shown on the basic weld symbol. These dimensions are shown on the assembly drawing. See Figure 3-39. The depth of fi lling for a slot or plug weld is shown inside the weld symbol. In Figure 3-39, the depth of fi lling for the slot weld is 1/2″. If there is a series of plug or slot welds, the center-to-center distance is shown to the right of the weld symbol. The pitch (“P”), or center-to-center distance of welds, is presented to the right of the weld symbol. 3.5.12 Spot Welds A spot weld is another method of joining two or more pieces together with a weld not at the edge of a part. To set up a spot weld, parts are overlapped, usually in a lap joint. A weld is made at the surfaces where the parts contact. No hole or slot is cut into any of the parts. The weld can be made by resistance spot welding. The weld can also be made from one side by melting through the fi rst panel and melting into the second panel. The spot weld symbol is a small circle. The circle may be on either side of the reference line, or it may straddle the reference line. If the weld is accomplished from the arrow side, the weld symbol should be below the reference line, as in all other welding symbols. If the welding is done on both sides, as in resistance spot welding, the circle straddles the reference line. See Figure 3-40. Figure 3-37. Plug and slot welds. A—The hole and slot are shown as cut in one piece. B—Cross sections of the completed welds. C—The welding symbol for the plug and slot weld. A B C Figure 3-38. Plug weld symbol. A—Cross section of a completed plug weld. The desired dimensions are also shown. B—The weld symbol used to complete the desired weld. ∅.5 .25 45 B A .25″ 45° .5″