Have you ever had a finger, arm or leg put in a cast? And do you remember what you felt afterwards, when the bone had healed and they were about to remove the cast with the circular saw? Humanity (that's what they say these days...) is divided in half: those who are terrified that the blade will cut the skin underneath after the cast, and those who... lie!

Yet fortunately this whole operation is completely harmless because cast-removing saws are highly specialized tools, designed to perform their task without damaging the skin. How do they do it? The "trick" is that these circular blades do not actually rotate, but oscillate back and forth at incredibly high speeds. This oscillation is the key to their safety.

This alternating "back-and-forth" movement, about 3 mm wide, prevents the blade from cutting the skin, because the skin, which is quite elastic, moves in solidarity...