Sheet-metal tooling — where is clearance provided in piercing? In press-working, “piercing” creates a hole in the sheet by pushing a punch through the material. For piercing, the engineering clearance is normally provided on which tool element?

Introduction / Context:
Press operations like blanking and piercing rely on a precise gap between punch and die known as clearance. Correct allocation of this clearance affects burr height, punch load, tool life, and dimensional accuracy of either the hole (piercing) or the blank (blanking).

Given Data / Assumptions:

• Operation: piercing a hole (the retained work is the sheet with the hole).
• Goal: produce an accurately sized hole.
• Material: ductile sheet metals under shearing conditions.

Concept / Approach:
In piercing, the hole size is governed primarily by the punch size, because the punch displaces the material. To achieve the intended hole dimension, the punch is made to the nominal hole size, while the die opening is made larger by the clearance. Conversely, in blanking (where the blank is the product), the die opening equals the desired blank size and clearance is provided on the punch.

Step-by-Step Solution:

Verification / Alternative check:
Standard tooling charts specify die clearances as a percentage of stock thickness for piercing (e.g., 5–10% per side depending on material strength).

Why Other Options Are Wrong:

• Punch clearance for piercing would oversize the hole.
• Split or arbitrary clearances complicate maintenance and accuracy.
• Stripper plates guide/strip material; they are not clearance elements.

Common Pitfalls:
Confusing blanking with piercing; using insufficient clearance leading to high loads and poor edge quality.

Final Answer: