slot and plug weld - What is the difference between plug welding and slot welding? - Quora b888 slot

Answer (1 of 3): A plug weld is used to fasten two pieces of metal together using a welder. When joining the pieces, a hole is drilled into the top piece and it is laid over the bottom one. A weld is then made by running a bead inside of the drilled hole, thereby holding the two pieces together...

The number closer to the groove weld symbol (R) represents the size of the root or depth of metal filling for plug and slot welds.

You could also include pitch distance between centers of slots by putting on the right side of the plug weld symbol 1.78 - pitch, and a flat line contour symbol with a G to indicate grind flush.