To reiterate, fillet weld gauges do not measure fillet welds. The gauges are used to determine whether the weld is smaller than, larger than, or the exact size of the gauge being used. The set of leaves of the fillet weld gauges are a collection of “go/no-go” gauges. The inspector sizes the fillet weld by comparing the size of the weld to the size of several gauges until the inspector finds a gauge where the weld is slightly larger than the gauge. Most welding standards include a statement to the effect the required weld size is as specified by the welding symbol. Dig a little deeper into the welding standard, and there may be provisions permitting a weld to be slightly smaller by some fraction or percentage of the specified weld size. The inspector’s task is to determine what the smallest permitted weld size is and then verify all the fillet welds are at least as big as the smallest weld size permitted. Let us say the welding 16 Inspection Trends / January 2011 symbol specifies the weld size as 9⁄16 in. The welding standard allows the weld to under run the specified weld size by 1⁄16 in. The smallest weld permitted would be the specified size minus the allowable under run or 9⁄16 – 1⁄16 = ½ in. The inspector would select the ½-in. fillet weld gauge and check the weld legs (if the weld is convex) or the weld throat (if the fillet weld is concave). The welds would then be declared undersized if the welds were less than ½ in. or they would be accepted if they were ½ in. or larger. The following figures depict the conditions the inspector might find during an inspection. Figure 6 depicts an undersized convex fillet weld, and Fig. 7 shows a concave fillet weld that is undersized under the defined constraints. Figures 8 and 9 depict fillet gauges sizing welds that meet the minimum size requirement. Both the convex and concave fillet welds are acceptable if both legs of the convex fillet weld are found to be the proper size or in the latter case, the throat is the proper size. Figure 10 shows a convex weld and a concave weld that are larger than the ½-in. fillet weld gauge used to check the weld sizes. Let me now interject my personal philosophy on how to verify the size of a fillet weld when using the leaf-type fillet gauge. In the example provided, we determined the smallest acceptable weld size is ½ in. based on the stipulations of the welding standard. We also noted that the gauges are available in 1⁄16-in. increments up to ½ in. I do not interpolate the weld size when I use these fillet weld gauges. To put it another way, the weld is either smaller than the weld gauge, the same size as the weld gauge, or the weld is larger than the size of the gauge being used. I do not round the “measured” weld size up to ½ in. if the weld appears to be more than 15⁄32 in., i.e., 1⁄32 Fig. 9 — Concave fillet weld size is the same as the fillet weld gauge. Fig. 10 — The convex (top) and concave fillet welds are larger than the size indicated by the fillet weld gauge. Fig. 11 — Modified fillet weld gauge used for measuring the leg of the fillet weld in a skewed joint.
Inspection Trends - January 2011 - Winter
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