Acro News

Hole Diameter vs. Material Thickness

One driving factor when it comes to the cost of metal parts is the diameter of a hole required to be punch in its relation to the thickness of the material.  In order to be able to stamp most cost effectively the hole diameter should be at least 1.5 times the thickness of the material (this is especially important in harder materials like Stainless Steel).  The diagram below shows how those forces spread out and not down through the material.  When smaller holes are required they can sometimes be punched using specialized punches if the diameter is just under 1.5 thickness (however this also causes the parts to run more slowly / more expensively).  When the required diameter is less than the material thickness often the holes need to be produced in a second operation (sometimes drilling or machining).

Hole Dia vs Thickness

When this rule is not followed and you still try to stamp there is a lot of force applied to the punches. The punches then get stuck and break or deform the parts (see example below of .096″ Holes in .122″ Material).  All these factors increase costs by slower run rate, more fall-out, and more maintenance.

Too Small Holes 2

So Where is the Cost Savings Possibility?

Can you live with a slightly larger diameter hole?

Can a slot be used instead of a round hole to spread the forces?

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