Butt joint
Two parts meet in the same plane. Used for plates, pipes and sections when a continuous connection is required.
Fabricator checkChoose the groove, root gap and edge preparation according to thickness, access and required penetration.
LEARN / WELDING FABRICATION
Welding joint types: a practical guide for fabricators.
Identify the joint, choose the weld type, plan the preparation and check the finished connection. This guide is written for workshop decisions—not just textbook definitions.
01 / JOINT GEOMETRY
Start with how the parts meet.
Joint geometry affects access, weld size, edge preparation, distortion and how loads move through the fabrication.
Lap joint
One part overlaps another. Common for sheet metal, brackets and repairs where a simple overlap is practical.
Fabricator checkControl overlap, heat input and seal quality to reduce distortion and crevice corrosion.
Tee joint
One part meets another at approximately 90 degrees. Frequently used for frames, stiffeners, supports and structural fabrication.
Fabricator checkFillet size, access and load direction matter more than simply making the weld look large.
Corner joint
Two parts meet at an outside or inside corner. Used for boxes, trays, frames and enclosures.
Fabricator checkDecide whether the corner needs a fillet, groove or continuous seal weld before fabrication.
Edge joint
Parallel edges are joined along their sides. Suitable for light-gauge sheet and non-structural assemblies.
Fabricator checkIt is useful for sheet work but is not automatically suitable for heavily loaded connections.
02 / WELD TYPE
Then select how the joint will be welded.
Fillet weld
A triangular weld joining surfaces at an angle, especially tee, lap and corner joints.
Groove weld
A weld placed in a prepared groove between two members, commonly used for butt joints.
Plug weld
A weld made through a hole in one part to join it to the part beneath, often used in sheet fabrication.
Slot weld
A weld made through an elongated slot to transfer load or join overlapping components.
Seal weld
A weld intended to prevent leakage or ingress; it should not be assumed to provide structural strength.
03 / PROCESS SELECTION
Match the welding process to the job.
MIG / GMAWFast production work, mild steel, stainless steel and aluminium when wire, shielding gas and settings are matched.
TIG / GTAWClean, controlled welds on stainless steel, aluminium and thin sections where appearance and heat control matter.
Stick / SMAWOutdoor work, repair work and thicker sections where portability and tolerance to site conditions are important.
Flux-cored / FCAWHigh deposition and fabrication work, with the correct wire, polarity, shielding and fume controls.
Preparation checklist
- Confirm material grade, thickness and condition.
- Clean oil, paint, rust, moisture and surface contamination.
- Check fit-up, alignment, root gap and tack-weld sequence.
- Choose edge preparation and root face for the required penetration.
- Plan welding position, access, preheat, interpass temperature and distortion control.
- Use the drawing, WPS and applicable code for production-critical work.
Common welding defects
PorosityOften linked to contamination, moisture, shielding problems or excessive arc length.
UndercutMay result from excessive current, travel speed, arc length or poor manipulation.
CrackingRequires serious investigation of material, restraint, hydrogen, heat control and procedure.
DistortionManage with sequence, balanced welding, fit-up, restraint and controlled heat input.