Why do scissors only work in one hand and not the other?
In: Engineering
The primary difference between left and right handed scissors is the way the blades are connected. The special thing about scissors for left hands is that when you open them, the blade on the left hand side goes to the top. This means the blade on the right sits on the bottom.
Scissors are like gloves that don’t come in pairs. If you want to use scissors in your left hand you have to buy left handed scissors! Most people are right handed, so that’s why there’s so many more right than left handed scissors.
When cutting there is a slight sideways force not just the squeezing. In the opposite hand it’s difficult to apply the opposite sideways force.
Scissors, and the motion you make while using them are more complex than they might initially seem. If you look between the blades of good quality scissors as you open and close them, you’ll notice that they only actually touch in one spot, that moves along the blades as they slice. Getting the blades to touch in this way requires both a fairly complex twist and curvature on the blades, and a slight sideways force you apply with your hands. Usually you learn to apply this sideways force as you cut with scissors as a child, and do it without thinking about it. The thing is, your hand can only really apply this force efficiently in one direction, and the direction it needs to be in is determined by which blade is closer to you. So, right- and left-handed people need scissors that are mirror images of each other if they want to be able to use them well.
The force you apply to the two handle pieces of a pair of scissors, isn’t a totally flat force parallel to the cutting plane. You’re also pushing with your thumb and pulling with your fingers laterally, to create a stabilizing pair of opposing sideways forces.
When you’re using the scissors in the correct hand, those opposing forces are directed so as to pinch the cutting edges together as they swivel. In the wrong hand, it splays them apart instead.
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