A common tool used in visual
examination of weldments is the weld fillet gage. This simple, easy-to-use device measures leg lengths and determines if there is sufficient throat in weld fillets. This gage is basically a comparator — the acceptable size is etched into the gage and arcs are cut into the gage to allow space for the weld bead. The gage is placed square against the welded components and the actual weld is compared to the
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FIGURE14: Direct reading caliper.
FIGURE15. Mechanical gage, or micrometer.
Anvil Spindle Clamp ring 0 Screw Ratchet Thimble Barrel Frame
standards of the gage (Fig. 16). This type of gage offers a quick and precise means of measuring concave and convex fillet welds from 3 mm (0.13 in.) to 25 mm (1.0 in.).
Weld gages (Fig. 17) designed to measure offset displacement can be used to measure the size of fillet welds, the actual throat size of convex and concave fillet welds, reinforcement of butt welds and root openings of 8 mm (0.3 in.) and 3 mm (0.13 in.)
Another more versatile device used for weld inspection is the welding gage, commonly referred to as the cambridge gage. The Welding Institute, Cambridge, United Kingdom, developed this versatile tool — hence the name. With this device, joint preparation angles, joint
misalignment, weld fillet size and depth measurements can be easily obtained. Figure 18 shows some typical applications.
This volume’s chapter on electric power applications includes some discussion of weld gaging.
Tolerance Standards
2The physical features of an object (form, profile, orientation, location and size) must be controlled. The blueprint or drawing for the object must specify the
attributes of each characteristic including tolerances. Requirements are specified and variations are assessed by using geometric dimensions and tolerances, uniformly communicated in a consensus standard. Dimensional tolerances are related to issues of surface roughness and waviness, discussed above, and are governed by some of the same standards.6,7,11Working to a consensus standard realizes the following benefits.
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FIGURE16. Fillet weld gage: (a) concave weld; (b) convex weld.
Leg length
(a)
(b)
FIGURE17. Displacement weld gaging: (a) leg length of fillet weld; (b) convexity of fillet weld; (c) concavity of fillet weld; (d) bead height of butt weld.
(a)
(b)
(c)
1. Computerized design tools, such as computer aided design (CAD) systems, are more feasible. The designer must have a complete understanding of inspection principles to properly apply geometric tolerancing principles. For designers to use points in space as construction points in their drawing can be a liability during
manufacturing and inspection.
2. The part may be allowed to have the maximum possible tolerances while ensuring interchangeability and fit to other pieces. This will enhance the producibility and lower costs. 3. The specification of a consensus
tolerance standard in the working procedures helps to answer concerns about quality and, in the event of material failure, about liability. 4. Controversy during manufacturing
and inspection is reduced when the application of the design requirements is done consistently. Part tolerances can be established with regard to the part’s functional surfaces. This consistency allows functional
inspection gaging and manufacturing fixturing.
Consistency is generally accomplished in relation to datums and datum surfaces that serve as orientation or zero points. The datum plane or surface is the actual feature of the part used to establish the datum. A datum is a theoretically perfect point, axis, or plane derived from actual features. Any feature has variation. Datums are specified on the drawing and are controlled by establishing three separate datums to create an X,Y,Z coordinate system. Geometrically, three points establish a plane, two points establish a line and one point establishes a point in space. This arrangement is also called a 3,2,1 coordinate system.
Tolerances of orientation include requirements for perpendicularity, angularity or parallelism.
Tolerances of form include
requirements for flatness, straightness, circularity and cylindricity. A feature has form only in terms of its relationship to itself. For example, the requirement for a flat surface means that each point on the surface must be within the specified band in terms of every other point of that surface. Any point on the surface is independent of any other surface.
Profile tolerances include the
requirements for the profile of a line and the profile of a surface.
Basic dimensions are used to describe the theoretically exact size, profile, orientation, or location of a feature. They prevent ambiguity when describing the variation allowed in a feature. Size can be specified as a linear dimension, a
diameter, a radius, an angle or any other quantity of size.
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FIGURE18. Cambridge gage: (a) zero to
60 degree angle of preparation; (b) excess weld metal in reinforcement; (c) pitting or depth of undercut; (d) fillet weld throat size; (e) high/low misalignment.
(a) (b) (c) (d) (e) 50 MM IN MM IN MM IN MM IN MM IN 60
1. Bailey, W.[H.] Part 3, “Vision and Light.” Section 1, “Fundamentals of Visual and Optical Testing.”
Nondestructive Testing Handbook, second edition: Vol. 8, Visual and Optical Testing. Columbus, OH: American Society for Nondestructive Testing (1993): p 9-21.
2. Sayler, G.[C.] ASNT Level III Study Guide: Visual and Optical Testing Method. Columbus, OH: American Society for Nondestructive Testing (1998, revised 2006).
3. Krauss, D.G. ASNT Level II Study Guide: Visual and Optical Testing Method. Columbus, OH: American Society for Nondestructive Testing (1998). 4. Chapter 4, “Basic Visual Aids and
Accessories for Visual Testing”: Part 3, “Magnifiers.” Nondestructive Testing Handbook, second edition: Vol. 8, Visual and Optical Testing. Columbus, OH: American Society for
Nondestructive Testing (1993): p 76-81.
5. Benford, J.R., L.E. Florry and A.A. Levin. Section 11, “Visual Inspection Equipment.” Nondestructive Testing Handbook, first edition. Columbus, OH: American Society for Nondestructive Testing (1959). 6. ISO 2768, General Tolerances. Geneva,
Switzerland: International Organization for Standardization (1989).
7. BS EN 22768-1, General Tolerances. Brussels, Belgium: European
Committee for Standardization (1993). 8. ANSI B46.1, Surface Texture (Surface
Roughness, Waviness, and Lay). New York, NY: American National Standards Institute (2000). 9. ANSI Y14.5M, Dimensions and
Tolerancing. New York, NY: American National Standards Institute (2000). Superseded by ASME Y14.5M. 10. ISO 1302, Geometrical Product
Specifications (GPS) — Indication of Surface Texture in Technical Product Documentation. Geneva, Switzerland: International Organization for Standardization (2002). 11. ASME Y14.5M, Dimensions and
Tolerancing. New York, NY: American Society of Mechanical Engineers (2009). Supersedes ANSI Y14.5M.
12. Aizawa, H. and K. Miyagawa.
Section 8, “Applications of Visual and Optical Tests in the Metals Industries”: Part 2, “Visual and Optical Testing in the Steel Industry.” Nondestructive Testing Handbook, second edition: Vol. 8, Visual and Optical Testing. Columbus, OH: American Society for Nondestructive Testing (1993): p 228-243.
13. CIE S 014-2; ISO 1164-2, CIE Standard llluminants for Colorimetry. Wien, Österreich [Vienna, Austria]: Commission Internationale de l’Éclairage [International Commission on Illumination (CIE)] (2006).
Bibliography
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Dunn, D. Chapter 3, “The Visual and Optical Testing Environment”: Part 2, “Environmental Factors.”
Nondestructive Testing Handbook, second edition: Vol. 8, Visual and Optical Testing. Columbus, OH: American Society for Nondestructive Testing (1993): p 54-56.
Hecht, E. Schaum’s Outline of Theory and Problems of Optics. New York, NY: McGraw-Hill (2007).
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ISO 3058, Non-Destructive Testing — Aids to Visual Inspection — Selection of
Low-Power Magnifiers. Geneva, Switzerland: International Organization for
Standardization (1998). Johnson, B.K. Optics and Optical
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