Question

A blanking operation is to be performed on 2.0 mm thick cold rolled steel (half hard). The part is circular with diameter = 75.0 mm. Determine the appropriate punch and die sizes for this operation.

Answer 1

Answer:

The punch size is 74.70 mm

The die size is 75 mm

Explanation:

From the table of allowance, the allowance for cold rolled steel ($A_c$) is given as 0.075.

Given that: thickness = 2.00 mm, blank diameter ($D_b$)= 75.0 mm

The clearance (c) is the product of allowance and the thickness of the cold rolled steel. It is given by:

$c=thickness*A_c=2\ mm(0.075)=0.15\ mm$

The die diameter is equal to the blank diameter and the punch diameter is smaller than the blank diameter by twice the clearance

Punch diameter = $D_b-2c=75\ mm-2(0.15)=75\ mm-0.3\ mm = 74.70\ mm$

Die diameter = $D_b=75\ mm$

the appropriate punch diameter is 74.70 mm and die size is 75 mm

Answer 2

The appropriate punch and die sizes for the given operation are;

Punch diameter = 74.7 mm

Die diameter size = 75 mm

We are given;

The allowance for the cold rolled steel is not given but we will adopt a general value of;

a = 0.075.

Thus;

Clearance is;

c = 2a

c = 2 × 0.075

c = 0.15

We are given;

Diameter of part; d_b = 75 mm

Formula for punch diameter is;

d_h = d_b - c

d_h = 75 - 0.15

d_h = 74.85 mm

Meanwhile, the die diameter is 75 mm.

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