Calculate the smallest punch diameter that can be designed

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Calculate the smallest punch diameter that can be designed for piercing sheet metal strip with the following data. Crushing strength of the punch material is 1500 MPa. Thickness of the sheet is 2 mm, factor of safety is 3, shear strength of the sheet material 500 MPa is

1. 2 mm
2. 6 mm
3. 8 mm
4. 24 mm

Correct Option: C

Punching force = τ = πdt
= crushing strength [FOS = 3]

Force =	1500	×	π	d²
	3		4

1500	×	π	d² = 500 × π × d × 2
3		4

d = 8 mm