Sheet-metal operations — definition of piercing: In press working terminology, piercing is the operation of cutting

Introduction / Context:
Punching operations are categorised by which part is retained as the product. Accurate terminology avoids confusion in tooling design, cost estimation, and scrap handling. Piercing and blanking are frequently confused in introductory manufacturing courses.

Given Data / Assumptions:

• A punch–die set operates on sheet/strip metal.
• Clearance is correctly set for material and thickness.
• We are classifying the operation by the intended product.

Concept / Approach:
In piercing, a hole is created in the sheet; the removed piece (slug) is scrap. The hole may be circular or of any other profile. In blanking, the piece that is cut out (the blank) is the product, and the remaining sheet is scrap. Multiple-hole patterns are achieved by multiple hits or special tooling but are still fundamentally piercing operations.

Step-by-Step Solution:
Define piercing: create a hole; keep the sheet; discard the slug.Contrast with blanking: keep the slug (blank); discard the surrounding sheet.Recognise that shape can be circular or non-circular; piercing is not limited to cylinders.Hence, the correct definition is cutting a hole of any required shape using punch and die with slug as scrap.

Verification / Alternative check:
Tooling handbooks classify piercing and blanking based on which portion is retained; example drawings show identical punch/die but different intended products.

Why Other Options Are Wrong:
Restricting to cylindrical holes is unnecessary; any shape can be pierced.

Blanking describes making the product blank, not piercing.

Evenly spaced patterns can be produced, but that is not the defining feature.

Punching does not create threads; threading is a separate operation (tapping/forming).

Common Pitfalls:
Mis-setting clearance, causing burrs and short tool life; ignoring slug ejection and disposal; failing to support the sheet properly, leading to distortion around the hole.

Final Answer:
a hole of any required shape in sheet metal using a punch and die (the slug is scrap)