Joint design
Types of Welding Joints
There are five basic weld joint configurations — butt, lap, T, corner and edge — and the joint you pick decides how much preparation the parts need, how much filler the weld consumes, and how much load the finished connection can carry.
Type at least two characters. Press slash to focus this field.
The five joint types
Butt Joint
A butt joint places two members edge to edge in the same plane — the simplest joint to draw and the one that most…
Lap Joint
A lap joint overlaps two members and welds along the exposed edges — no edge preparation, forgiving fit-up, and the…
T-Joint
A T-joint sets one member perpendicular to the face of another, and it is normally filleted on both sides — the most…
Corner Joint
A corner joint brings two members together at their edges to form an L, and unlike a T-joint the upright lands on the…
Edge Joint
An edge joint lays two members face to face and welds along their common edge — a light-duty joint used to join…
Choosing a joint
| Joint | Preparation | Load capacity | Typical welds |
|---|---|---|---|
| Butt Joint | Square edge up to roughly 3/16 in; single-V above that; double-V, U… | A full-penetration butt joint develops the full strength of the base metal… | V-Groove Weld, Bevel-Groove Weld, U-Groove Weld |
| Lap Joint | None required beyond cleaning. | Loaded in shear rather than tension. | Fillet Weld, Plug Weld, Slot Weld |
| T-Joint | None for fillet welds. | Fillet capacity is governed by the throat, which for an equal-leg fillet is the… | Fillet Weld, Bevel-Groove Weld, J-Groove Weld |
| Corner Joint | None for a filleted corner. | Depends heavily on configuration. | Fillet Weld, V-Groove Weld, Bevel-Groove Weld |
| Edge Joint | Usually none. | Low. | V-Groove Weld, U-Groove Weld, Seam Weld |
Joint design questions
What are the five basic types of welding joints?
Butt, lap, T (tee), corner and edge. Every weld joint on a drawing is one of these five, or a variation on one.
Which welding joint is strongest?
A full-penetration butt joint, because it develops the full strength of the base metal. It also demands the most edge preparation and the most careful fit-up.
What is the difference between a T-joint and a corner joint?
Where the upright member lands. In a T-joint it meets the face of the other member somewhere in the middle; in a corner joint it meets the end, so the two form an L.
Which joint needs no edge preparation?
Lap, T and corner joints welded with fillets need none, which is why fillet welds are the cheapest to specify. Butt joints need preparation above about 3/16 in.
Does the joint type change which electrode I use?
Indirectly. An open-root butt joint wants a deep-penetrating electrode such as E6010; a positioned fillet can use a high-deposition rod like E7024. The joint sets the access and the penetration you need.