Plug weld
Applied to joint
Overlapping plates — plug weld through hole
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MIG welders for plug welds
Compact MIG units ideal for plug and slot weld applications.
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Description
A weld made in a circular hole in one member to join it to the surface of an overlapping member. The hole may be filled completely (full plug) or partially (partial fill). The hole is typically in the upper (arrow-side) member.
In plain English
Drill a round hole in the top plate, then fill it with weld metal to fuse to the plate underneath. The symbol is a rectangle on the reference line (it represents the hole, not the weld shape). Plug welds are used when you cannot get a fillet on the edge -- for example, joining a cover plate to a flange, or overlapping plates that need to be connected across their faces, not just at the edges. The hole diameter and depth of fill are specified on the symbol.
Symbol position
Rectangle symbol on the reference line. Arrow side indicates which member has the hole.
Size notation
Hole diameter 'd' to the left. Depth of fill shown inside the symbol if partial. Pitch shown to the right if multiple plug welds in a pattern.
Common uses
- Cover plate to flange connections
- Sheet metal lap joints where edge fillets are not possible
- Reinforcement plate attachments
- Repair welds filling holes in plate
