1.1 The digital reference images provided in the adjunct to this standard illustrate various types and degrees of discontinuities occurring in thin-wall steel investment castings.2 Use of this standard for the specification or grading of castings requires procurement of the adjunct digital reference images which illustrate the discontinuity types and severity levels. They are intended to provide the following: 1.1.1 A guide enabling recognition of thin-wall steel casting discontinuities and their differentiation both as to type and degree through digital radiographic examination. 1.1.2 Example digital radiographic illustrations of discontinuities and a nomenclature for reference in acceptance standards, specifications and drawings. 1.2 Two illustration categories are covered as follows: 1.2.1 Graded—Six common discontinuity types each illustrated in eight degrees of progressively increasing severity. 1.2.2 Ungraded—Twelve single illustrations of additional discontinuity types and of patterns and imperfections not generally regarded as discontinuities. 1.3 The reference radiographs were developed for casting sections up to 1 in. (25.4 mm) in thickness. 1.4 All areas of this standard may be open to agreement between the cognizant engineering organization and the supplier, or specific direction from the cognizant engineering organization. These items should be addressed in the purchase order or the contract. Note 1: The set of digital reference images consists of 16 digital files, software to load the desired format and specific instructions on the loading process. The 16 reference images illustrate eight grades of severity in six common discontinuity types and twelve ungraded discontinuities and contain an image of a step wedge and two duplex-wire gauges. Available from ASTM International Headquarters. Order number RRE2660. Refer to Practice E2002 for wire pair details. 1.5 The