Casting defects — definition of fin (flash) Evaluate the statement: “Fin is a casting defect consisting of thin, unwanted projections of metal not intended as part of the casting.”

Introduction / Context:
Defect identification is essential for casting quality. A “fin” (often called flash) appears as a thin metallic sheet or burr along parting lines, core joints, or cracks in the mould where metal seeps into unintended gaps.

Given Data / Assumptions:

• Sand or permanent mould casting environment.
• Fin arises from mould mismatch, excessive ramming, worn parting surfaces, or high metal pressure.
• The statement describes thin projections not part of the design.

Concept / Approach:
During pouring, liquid metal seeks any available gap. If the mould halves do not mate perfectly or if cracks exist, metal enters and solidifies as a thin film. These fins must be removed in fettling and indicate process variables that need correction (mould hardness, clamp force, parting surface condition, gating pressure).

Step-by-Step Solution:
Compare the statement with standard defect definitions: a fin equals flash — thin sheet-like projection.Identify causes: poor mould alignment, high metallostatic head, worn mould, or inadequate clamping.Confirm that fins are defects and not functional features like risers or gates.

Verification / Alternative check:
Quality manuals list fins/flash with corrective actions such as improving mould closure, repairing parting surfaces, reducing pouring temperature or head, and optimizing sand properties.

Why Other Options Are Wrong:
Fins are not feeders (risers), not gas holes, and not shrinkage cavities. They also occur across casting processes, not only die casting.

Common Pitfalls:
Confusing fins with mismatch offset; ignoring that persistent fins increase machining time and safety hazards; overcompacting sand causing mould cracks.

Final Answer:
Correct — fins are thin unwanted metal projections (flash) due to mould mismatch or cracks