AskUs: Why is a Guillotine’s blade always angled?

So one of our readers asked us this question the other day: Why is a Guillotine’s blade always angled?

ANSWER

Angled blade slices, rather than chopping. A human neck doesn’t have a super tough skin, but there are tougher bits relative to other bits and the bits are often discrete, meaning if you succeed in cutting one bit, you can chalk it up as job done and move onto the next bit, one at a time.

Imagine you are cutting a tomato. The skin of the fruit is somewhat harder for a knife blade to get through compared to the ‘guts’. Now if you take your knife and press down, your blade will compress the soft ‘guts’ and you will increase the length of blade that encounters the skin. Its like your blade is staying as sharp (or dull) while the skin is getting tougher.

But what if you take your knife and, like the famous guillotine blade, angle it to the direction of force/resistance? You drastically lessen the amount of blade that can come into contact with the skin if it compresses. Its, not perfect of course, but it does the best job of keeping more of the force directed on singular points.

Why aren’t all blades like this? Well they often are and it is called a “shearing angle”. When you angle the blade you decrease the surface area drastically. And if you are cutting a super-duper sized neck, well then friction starts holding your blade back.

Imagine cheese. Not particularly hard to cut, but if you use a butchers knife it will seem difficult. The cheese “sticks” to the big flat blade holding it back and making your job difficult. This is why cheese cutters are often skinny little pieces of wire. The wire isn’t particularly sharp, it doesn’t have to be. Nor is it very strong, there are no vertebrae in a cheddar wheel. But it has almost no surface area, so it can just slide right through!