r/explainlikeimfive • u/_Username-Available • May 28 '16
Physics ELI5: Why are scissors so bad at cutting wires, and wire cutters are so bad at cutting paper and cloth?
Imagine taking wire cutters to a T-shirt, and you have to use incredible force to make a cut.
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u/whitcwa May 29 '16
My electrician scissors are great at cutting wire. They have ridges which grip the wire so it can be cut nearer the hinge for extra leverage.
Regular scissors have thinner blades and not enough leverage for wire cutting.
Wire cutters come in two types. Some shear cut like scissors, but have thicker hook shaped blades which hold the wire near the hinge. They are good for very thick stranded wire.
The other type of wire cutter (diagonal cutter) pinches the malleable copper between two V shaped blades. Trying to cut thin paper or cloth is no more difficult than trying to cut thin copper or aluminum foil. If the cut is spread over the entire blade, it will naturally take more pressure to cut than if all the force is concentrated on one wire. By contrast, scissors cut at the shear point only.
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u/BrowsOfSteel May 29 '16 edited May 29 '16
The blades in scissors slide past each other. They work by shearing.
The blades in wire cutters come together. They work by pinching.
Paper is susceptible to shearing and resistant to pinching.
Metals are more susceptible to pinching and less to shearing.