Copyright Goodheart-Willcox Co., Inc. Chapter 17 Welding Procedures, Defects, and Corrective Actions 147 The ripples left by the weld pool should be evenly spaced, without high and low areas or undercut at the weld toe. A special inspection tool can be used to check undercut depth, crown height on a butt weld, and drop-through on the penetration side of the butt weld. See Figure 17-5 and Figure 17-6. Liquid Penetrant Inspection Liquid penetrant inspection is a nondestructive test performed on the surface of a weld or the pene- tration side of a butt weld. Colored liquid or fluores- fl cent dye penetrant is applied to the weld. Some of the penetrant seeps into any cracks or pits, and the pene- trant left on the surface is wiped away. Liquid devel- oper is applied, drawing some of the penetrant out of the crevices. The dye permits defects to be seen. See Figure 17-7 and Figure 17-8. Goodheart-Willcox Publisher Figure 17-3. A fillet weld gauge is used to check if both leg sizes are within tolerance. Goodheart-Willcox Publisher Figure 17-4. Throat size is used to determine concavity or convexity of the weld. Goodheart-Willcox Publisher Figure 17-5. This gauge measures the reinforcement on the weld face. This weld face reinforcement is within tolerance. Goodheart-Willcox Publisher Figure 17-6. The gauge shows that this weld root reinforcement is excessive and unacceptable.