Technologies
A fillet weld is a triangular-cross-section weld that joins two metal pieces meeting at an angle—typically 90°—without requiring edge preparation. It is the most common weld type in structural and she
A fillet weld is a triangular-cross-section weld that joins two metal pieces meeting at an angle—typically 90°—without requiring edge preparation. It is the most common weld type in structural and sheet metal fabrication, covering T-joints, lap joints, and corner joints, and is governed by standards
A fillet weld is a triangular-cross-section weld that joins two metal pieces meeting at an angle—typically 90°—without requiring edge preparation. It is the most common weld type in structural and sheet metal fabrication, covering T-joints, lap joints, and corner joints, and is governed by standards including AWS D1.1 and ISO 2553.
Fillet weld size is determined by two measurements: the leg size (the distance from the root to the toe along the base metal) and the effective throat (the shortest distance from the root to the face of the weld). For an equal-leg 45° fillet, the effective throat equals 0.707 × the leg size—this formula separates engineering-grade specifications from guesswork. AWS D1.1 specifies minimum leg sizes by base metal thickness: a 6 mm minimum leg applies to base metals between 12 mm and 20 mm thick. At Entag, we hold weld leg size tolerances to ±0.5 mm on production sheet metal parts, with post-weld flatness controlled to ISO 13920 class B—a tolerance procurement managers can specify in a drawing callout without rework risk.
Three joint configurations dominate sheet metal fabrication:
Parts fabricated from laser-cut sheet metal are ideal candidates for fillet welding because laser-cut edges have minimal burr and require no bevelling, reducing setup time and cost.
| Attribute | Fillet Weld | Groove Weld | Plug/Slot Weld |
|---|---|---|---|
| Edge preparation required? | No | Yes (bevelling) | No |
| Joint types suited | T, lap, corner | Butt, T (full penetration) | Lap only |
| Relative cost | Low | Medium–High | Medium |
| Strength (equal throat) | Good (shear plane) | Highest (full penetration) | Moderate |
Fillet welds are lower cost because they require no edge bevelling and simpler filler metal management. Groove welds deliver maximum strength but demand precision edge preparation and higher heat input. For most sheet metal applications in Cairo, Alexandria, Jeddah, Riyadh, and Dammam, fillet welding provides sufficient strength at 40–50% lower fabrication cost. Engineers should specify groove welds only when full-penetration strength is required by design load or pressure vessel code (ASME Section VIII).
Entag's sheet metal fabrication service handles fillet welding in mild steel (S235/S275 per EN 10025), stainless steel (304/316L), and aluminium alloys, with weldable thicknesses from 1.5 mm up to 20 mm. Each material requires matched filler metal: solid wire MIG for mild steel and aluminium (faster, suitable for production runs), TIG for stainless steel and critical assemblies (higher quality, lower deposition rate). Post-weld distortion is controlled to ISO 13920 class B (flatness deviation ≤ 3 mm per metre) for general structural parts, or class A (≤ 1.5 mm per metre) for precision assemblies. For CNC machining services in Egypt on pre-weld or post-weld components, our integrated capabilities ensure seamless coordination.
What is the difference between a fillet weld and a groove weld?
A fillet weld joins pieces at an angle using a triangular bead with no edge preparation, making it faster and lower cost. A groove weld requires bevelling base metal edges to achieve full or partial penetration, delivering higher tensile strength. For most sheet metal brackets and frames, fillet welds provide sufficient strength at lower cost. AWS D1.1 design tables and ISO 2553 standards govern both processes.
How do you calculate fillet weld leg size?
Fillet weld leg size is determined by the required throat thickness, material thickness, and applied load. The effective throat equals 0.707 × the leg size for an equal-leg 45° fillet. AWS D1.1 specifies minimum leg sizes by base metal thickness—for example, 6 mm minimum leg for base metals between 12 mm and 20 mm thick. Leg size tolerance of ±0.5 mm is standard in production.
What materials can be fillet welded?
Fillet welding is suitable for mild steel (S235/S275), stainless steel (304/316L), and aluminium alloys. Each material requires matched filler metal and process parameters—MIG for mild steel and aluminium, TIG for stainless steel and precision work. Entag handles all three material families with certified welders across Egypt and Saudi Arabia.
What tolerances are held on fillet welds in production parts?
In production sheet metal fabrication, fillet weld leg size is typically held to ±0.5 mm of the drawing callout, with post-weld flatness controlled to ISO 13920 class B for general structural applications or tighter for precision assemblies requiring ≤ 1.5 mm per metre deviation.
When should you use a double-sided fillet weld instead of single-pass?
A double-sided fillet weld (applied to both sides of a T-joint or lap joint) is significantly stronger than a single-pass weld and is required when applied loads exceed the shear capacity of one bead. AWS D1.1 design tables specify which joint configurations and thicknesses demand dual-sided welding. For complex assemblies, tube fabrication services often combine single and dual-sided fillets depending on structural demand.
What is ISO 13920 and why does it matter for welded parts?
ISO 13920 defines tolerances and geometric deviations for welded assemblies. Class B applies to general structural work; class A applies to precision assemblies. It controls post-weld flatness, straightness, and distortion—critical for parts that must fit with other components or function in tight mechanical assemblies. Compliance eliminates rework and integration delays.
Ready to start your project? Request a quote on Entag—upload your CAD file and get a price in 24 hours. Entag's sheet metal fabrication in Egypt covers fillet welding across Egypt and Saudi Arabia, with fast turnaround and ISO 13920 quality control on every part.
