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Lap Joint
A weld joint in which two overlapping pieces of material are joined, typically with fillet welds on one or both sides. Lap joints are common in sheet metal and structural plate applications where simple, lower-strength connections are acceptable.
Lap joints are frequently selected in manufacturing when simplicity and speed take priority over maximum strength efficiency, because two overlapping surfaces can be joined with fillet welds on one or both sides without requiring joint preparation. The overlapping configuration inherently creates stress concentration at the termination of the weld; long lap lengths distribute this stress more favorably than short overlaps.
In sheet metal assembly, lap joints appear everywhere, from corner connections in NEMA enclosures to attachment lugs on tanks, where the weld leg size is controlled to match the thinner of the two materials being joined. A lap joint with dual-sided fillets offers improved fatigue performance and load distribution compared to single-sided applications, though the added welding time and finishing labor must be justified by the operational demands of the assembly.
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