When adjusting the flaw locating rule for a shear wave weld inspection, the zero point on the rule must coincide with the:

• A. Sound beam exit point of the wedge
• B. Point directly over the flaw
• C. Wheel search unit
• D. Circular scanner

Answer: (A)

In flaw locating with shear-wave weld inspections, the zero point on the rule is the reference from which you convert time to distance along the weld. The beam’s travel path begins when it exits the wedge and enters the material, so setting the zero at the wedge exit aligns the time-of-flight measurement with the actual distance traveled inside the part. This accounts for the fixed delay the wedge introduces and makes the rule accurately map to flaw location along the weld. If the zero were placed elsewhere, such as at the flaw itself, the wheel or scanner, the time-to-distance conversion would be offset and flaws would be mislocated.