Question

A $\varphi 25mm$ hole is pierced in a $t=2.5mm$ thick steel sheet having shear strength $\tau =350MPa$. If the diametral clearance is given by the expression $c=0.0064\sqrt{\tau }$, the die diameter (in $mm$), punch diameter (in $mm$) and punch force in $\left(kN\right)$ respectively are

• A. $25.0,25.3,171.8$
• B. $25.0,24.7,68.75$
• C. $24.7,25.0,171.8$
• D. $25.3,25.0,68.75$

Answer 1

The correct option is D $25.3,25.0,68.75$

Given, $t=2.5mm,\tau =350MPa$
$d_{hole}=25mm$
Punch dia $=$ Dia of hole $=$ $25mm$
Diametral clearance
$=0.0064\times$ 2.5 $\times$ $\sqrt{350}$
$=0.299\approx 0.3mm$
Die dia $=$ Punch dia $+$ Clearance
=$25+0.3=25.3mm$
Punch force $=\pi dt\tau =\pi \times 25\times 2.5\times 350$
$=68.72kN$