In a 90-degree fillet weld, the throat length is approximately what fraction of the leg length?

In a 90-degree fillet weld, the throat length is approximately what fraction of the leg length?

• A. 0.5 of the leg length.
• B. 0.707 of the leg length.
• C. 0.9 of the leg length.
• D. 1.0 of the leg length.

Answer: (B)

In a fillet weld, the throat length is the shortest distance through the weld cross-section. For a 90-degree fillet, the weld cross-section forms an isosceles right triangle where both legs equal the leg length. The throat corresponds to the altitude from the right-angle vertex to the hypotenuse, and in an isosceles right triangle that altitude equals the leg length divided by the square root of 2. That’s about 0.707 times the leg length. So the throat length is approximately 0.707 of the leg length. The other fractions don’t match this geometric relationship for a right-angle fillet.

In a fillet weld, the throat length is the shortest distance through the weld cross-section. For a 90-degree fillet, the weld cross-section forms an isosceles right triangle where both legs equal the leg length. The throat corresponds to the altitude from the right-angle vertex to the hypotenuse, and in an isosceles right triangle that altitude equals the leg length divided by the square root of 2. That’s about 0.707 times the leg length. So the throat length is approximately 0.707 of the leg length. The other fractions don’t match this geometric relationship for a right-angle fillet.