MIL-DTL-12560K (MR)
6.3.7 Laps. A surface imperfection with appearance of a seam caused by hot metal, fins or sharp
corners being folded over and thus being forged or rolled into the surface but without being
welded.
6.3.8 Checks. Checks are numerous very fine cracks at the surface of a metal part. Checks may
appear during processing or during service and are most often associated with thermal cycling or
thermal treatment. They are also called check marks, checking, and heat checks.
6.3.9 Seams. A seam is an un-welded fold or lap that appears as a crack, usually resulting from a
discontinuity on a metal surface.
6.3.10 Blisters. A raised area, often dome shaped, resulting from delamination under pressure of
expanding gas trapped in a metal in a near sub-surface zone. Very small blisters may be called
pinhead blisters or pepper blisters.
6.3.11 Snakes. Any crooked surface imperfection in a metal plate, resembling a snake.
6.3.12 Cold shuts. Freezing of the top surface of an ingot before mold is full.
6.3.13 Burning. Burning is permanently damaged metal due to overheating enough to cause
incipient melting or intergranular oxidations. Note: this condition is usually obscured by normal
cleaning methods and would require deep pickling and/or metallography to note the continuous
oxidation (chicken wire effect) of the enlarged grain boundaries.
6.3.14 Lamination. A type of discontinuity with separation or weakness generally aligned
parallel to direction of the worked surface of the metal and may be the result of pipe, blisters,
seams, inclusions, or segregation; elongated and made directional by working.
6.3.15 Pit. A pit is a cavity or depressed area on the surface of a plate.
6.3.16 Linear indication. For nondestructive examination purposes, a linear indication is
evidence of a discontinuity that requires interpretation to determine its significance.
6.3.17 Thickness. The symbol "T" is used throughout this specification to indicate the nominal
thickness of the plate under consideration.
6.3.18 Crack. A crack is a planar discontinuity in the metal that has length and is at least 0.002
inch deep. Cracks may be surface cracks or through cracks. For the purposes of this
specification, a crack is identifiable by the unaided eye unless otherwise specified in the contract
or purchase order (see 6.2).
6.3.19 Level II certification, as defined by ISO 9712. A Level II individual should be capable of
demonstrating competence to perform non-destructive testing according to established
procedures. Within the scope of the competence defined on the certificate, Level II personnel
may be authorized by their employer to:
a) Select the NDT technique for the test method to be used,
b) Define the limitations of application of the testing method,
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