What is the difference between a butt weld and a fillet weld?

What is the difference between a butt weld and a fillet weld?

• A. Butt weld joins two members end-to-end in the same plane; fillet weld fills an intersection with a triangular shape
• B. Butt weld uses filler metal; fillet weld does not
• C. Butt weld is decorative; fillet is structural
• D. Butt weld only for aluminum; fillet only for steel

Answer: (A)

The key idea is how the parts come together. A butt weld joins two pieces end-to-end in the same plane, so the weld bead runs along the seam where their ends meet and the outer surfaces stay flat and aligned. A fillet weld fills the corner where two parts meet at an angle (such as a T, corner, or lap joint), creating a triangular-shaped weld that bridges the gap between the members. This difference in joint geometry is what sets them apart. The other statements don’t fit because fillet and butt joints can both use filler metal or be welded without it depending on the process and material, and both types can be structural, not decorative or restricted to a single metal.

The key idea is how the parts come together. A butt weld joins two pieces end-to-end in the same plane, so the weld bead runs along the seam where their ends meet and the outer surfaces stay flat and aligned. A fillet weld fills the corner where two parts meet at an angle (such as a T, corner, or lap joint), creating a triangular-shaped weld that bridges the gap between the members. This difference in joint geometry is what sets them apart.

The other statements don’t fit because fillet and butt joints can both use filler metal or be welded without it depending on the process and material, and both types can be structural, not decorative or restricted to a single metal.