Blanking is a sheet metal cutting (shearing) operation in which a flat piece of metal (blank) is cut from a larger sheet using a punch and die. The cut-out blank is the useful product, while the remaining sheet is scrap, and the process is widely used in mass production of sheet metal components.

Blanking in Sheet Metal

Blanking is a widely used sheet metal cutting operation in which a punch and die are used to cut a flat piece (called a blank) from a larger sheet. Unlike shearing, the cut piece is the desired part, while the remaining sheet is usually scrap.

1. Definition of Blanking

Blanking is the process of punching a sheet metal strip or plate to produce a flat piece of a specific shape, which will be used as a finished part or intermediate component.

The material removed from the sheet is considered scrap.
The punch and die are designed to match the blank shape exactly.

Blanking cuts out a part from sheet metal to be used as a component.

2. Difference Between Blanking and Punching

Feature	Blanking	Punching
Desired Piece	The cut piece (blank)	The hole in the sheet
Scrap	Remaining sheet is scrap	Punched-out piece is scrap
Purpose	Produce parts like disks, plates, brackets	Create holes in sheets
Tooling	Punch and die match blank shape	Punch matches hole shape
Example	Blanking a washer from steel sheet	Punching a hole for a bolt

3. Mechanism of Blanking

Sheet metal is placed over the die.
Punch descends, applying force along the cutting edge.
Material deforms elastically, then plastically.
Shear stress exceeds shear strength, separating the blank from the sheet.
The blank falls through the die as the finished part.

Stages of Blanking:

Elastic deformation – Sheet bends slightly under punch.
Plastic deformation – Material flows along punch edge.
Fracture – Shear occurs along die edges, producing a clean blank.

4. Important Terminology in Blanking

Term	Definition
Blank	The piece cut out from the sheet (desired part)
Punch	Tool that pushes sheet into die to cut blank
Die	Tool that supports sheet and shapes the cut
Shear Force	Force required to punch out the blank
Clearance	Gap between punch and die (5–10% of sheet thickness)
Web	Material left between two adjacent blanks or holes
Burr	Rough edge remaining on blank or sheet

5. Blanking Equipment

Hand or Bench Press
- Manual operation for small blanks.
- Suitable for thin sheets (<3 mm).
Power Press / Hydraulic Press
- Motorized, high production rate.
- Can handle thick sheets and larger blanks.
Progressive Die Press
- Produces multiple blanks or shapes in one stroke.
- Efficient for high-volume production.

6. Factors Affecting Blanking

Material Type
- Ductile materials blank easily; brittle materials may crack.
Sheet Thickness (t)
- Thicker sheets require higher punch force.
Punch & Die Clearance
- Too small → excessive force, poor edge quality.
- Too large → excessive burrs, rough edges.
Punch Shape
- Sharp edges reduce force and produce clean blanks.
Cutting Speed
- Higher speed → cleaner edge, less distortion.
Lubrication
- Reduces friction, prolongs tool life, and improves edge finish.

7. Blanking Force Calculation

Where:

F = Shearing force (N)
τ = Shear strength of the material (N/mm² or MPa)
L = Length of cut or perimeter being sheared (mm)
t = Thickness of the sheet (mm)

Observation: Blanking force increases with thicker sheets, stronger materials, and larger blank perimeters.

8. Advantages of Blanking

Produces precise, uniform blanks.
Fast and suitable for mass production.
Minimal secondary operations if edge quality is good.
Can produce complex shapes with proper tooling.
Reduces material wastage compared to machining.

9. Disadvantages of Blanking

Requires high initial tooling cost.
Not suitable for very thick or hard materials without strong presses.
Burr formation may require secondary finishing.
Die wear occurs over time, affecting accuracy.

10. Applications of Blanking

Automotive parts – washers, brackets, panels
Electrical components – terminals, connectors
Industrial machinery – gaskets, flanges
Aerospace parts – aluminum panels and brackets
General sheet metal fabrication – disks, rings, plates

11. Summary

Blanking = cutting a desired part (blank) from sheet metal.
Unlike punching, the blank is the part we want, not the scrap.
Process involves punch, die, shear stress, and fracture.
Advantages: fast, precise, suitable for mass production.
Limitations: high tooling cost, not suitable for thick/hard materials, burr formation.

FAQ Section:

What is blanking in manufacturing?
Blanking is a metal cutting process in which a punch and die are used to cut a flat piece (blank) from a sheet or strip of material.
How does blanking differ from punching?
In blanking, the cut-out piece is the desired product, while in punching, the hole cut out is the intended feature, and the scrap is discarded.
What materials are commonly blanked?
Materials include steel, aluminum, copper, brass, and other sheet metals with sufficient ductility.
What equipment is used in blanking?
Blanking is typically performed using a press, with a punch and die assembly designed for the specific shape.
What are the advantages of blanking?
Advantages include high production speed, consistent shape and size, minimal finishing required, and suitability for mass production.
What are the limitations of blanking?
Limitations include initial tooling cost, material thickness restrictions, burr formation, and potential die wear.
What is a blanking die?
A blanking die is a specially designed tool that shapes and cuts the material into the desired blank.
What defects can occur in blanking?
Common defects include burrs, distortion, cracking, uneven edges, and die marks.
Is blanking a cold or hot process?
Blanking is usually a cold working process performed at room temperature.
What are typical applications of blanking?
Applications include manufacturing washers, metal plates, automotive parts, electrical components, and coinage.