Limitations on Plug and Slot Weld Dimensions

In material 5⁄8 in or less thick, the thickness of plug or slot welds should be the same as the material thickness. In material more than 5⁄8 in thick, the weld thickness should be at least half the material thickness but not less than 5⁄8 in.
Diameter of hole for a plug weld should be at least the depth of hole plus 5⁄16 in, but the diameter should not exceed minimum diameter  1⁄8 in, or 21⁄4 times the thickness of the weld metal, whichever is greater.

Slot welds may be spaced no closer than four times their width in a direction transverse to the slot length. In the longitudinal direction, center-to-center spacing should be at least twice the slot length.