For an 8 mm leg fillet weld, the throat length is approximately how many millimeters?

For an 8 mm leg fillet weld, the throat length is approximately how many millimeters?

• A. 6.5 mm
• B. 4.0 mm
• C. 8.0 mm
• D. 5.66 mm

Answer: (D)

Throat length is the perpendicular distance from the weld root to the weld face. For an equal-leg fillet weld, the cross-section forms an isosceles right triangle, so the throat equals the leg length multiplied by sin 45°, which is leg divided by √2. With an 8 mm leg, the throat is 8/√2 ≈ 5.66 mm. Therefore, the approximate throat length is 5.66 mm. The other values don’t fit this geometry: they either exceed the correct factor or correspond to the leg length itself rather than the perpendicular throat.

Throat length is the perpendicular distance from the weld root to the weld face. For an equal-leg fillet weld, the cross-section forms an isosceles right triangle, so the throat equals the leg length multiplied by sin 45°, which is leg divided by √2. With an 8 mm leg, the throat is 8/√2 ≈ 5.66 mm. Therefore, the approximate throat length is 5.66 mm. The other values don’t fit this geometry: they either exceed the correct factor or correspond to the leg length itself rather than the perpendicular throat.