Piercing Vs Blanking: Everything you need to know

Piercing and blanking are fundamental sheet metal cutting operations performed using a punch and die in a press machine.

Piercing is a process in which a hole is created in a sheet metal by forcing a punch through it. The removed material (called the slug) is scrap, and the remaining sheet is the useful part.
Blanking is a process in which a flat piece of metal (called the blank) is cut out from a larger sheet. In this case, the cut-out piece is the useful product, and the remaining sheet is scrap.

Both operations are widely used in manufacturing industries such as automotive, electronics, and appliance production for high-speed, accurate metal part fabrication.

Piercing and Blanking

Piercing and blanking are two closely related sheet metal cutting operations used to produce holes or parts from a metal sheet. Both are punch-and-die operations, but they differ in which part of the sheet is considered the useful product.

1. Blanking

1.1 Definition

Blanking is the sheet metal operation in which a punch removes a portion of sheet metal from the workpiece, and the removed piece (the blank) is the desired product, while the remaining sheet is scrap.

In short: The removed piece is useful.

1.2 Principle

A punch presses the sheet against a die opening.
The sheet is sheared along the die edges.
The blanked piece is ejected and collected for further processing.

1.3 Components Used

Punch – Shapes the blank.
Die – Provides cutting edge and supports sheet.
Stripper Plate – Holds sheet in position and ejects blank.

1.4 Applications of Blanking

Automotive parts (brackets, panels)
Gaskets
Coin manufacturing
Appliance components

1.5 Advantages

Produces accurate, uniform parts
High production rate
Suitable for mass production

1.6 Diagram of Blanking

   Punch
    |
    v
  __________
 |          |
 |  Sheet   |
 |__________|
      ^
      Die opening

(Removed blank is the product)

2. Piercing

2.1 Definition

Piercing is a sheet metal operation in which a punch creates a hole in a sheet, and the remaining sheet with the hole is the useful part, while the punched-out piece (slug) is scrap.

In short: The remaining sheet is useful.

2.2 Principle

The punch is forced through the sheet into the die.
A slug of metal is removed, creating a hole in the sheet.
The punched sheet is the final product.

2.3 Components Used

Same as blanking: Punch, die, stripper.

2.4 Applications of Piercing

Sheet metal panels with holes
Electrical enclosures
Perforated sheets
Decorative panels

2.5 Advantages

Precise holes
High-speed production
Can make multiple holes simultaneously (multi-piercing die)

3. Comparison Between Blanking and Piercing

Feature	Blanking	Piercing
Useful part	The piece removed (blank)	The remaining sheet
Scrap	Remaining sheet	Removed slug
Punch/Die	Similar tools	Similar tools
Application	Automotive panels, gaskets, coins	Perforated sheets, enclosures
Material flow	Removed portion is finished	Remaining sheet is finished
Tolerance	High	High

4. Shearing Process in Blanking & Piercing

Both operations are types of shearing:

Material is cut without melting.
Shear occurs along punch-die interface.
Clearance between punch and die is critical:
- Too small → Excessive force, tool wear
- Too large → Poor quality edges, burr formation

5. Conclusion

Blanking: Cut-out piece is the product.
Piercing: Sheet with holes is the product.
Both use punch and die, operate at high speed, and are widely used in mass production of sheet metal components.