The Difference Between Assisted and Automatic Opening Knives

Automatic knives (also known as switchblades) and assisted opening knives are often confused with one another because they tend to look the same to the untrained eye. However, understanding the difference between these two knives is important, because switchblades are illegal in some states and localities in the U.S. whereas assisted knives are legal in most areas.

How an Automatic Knife Works

In basic terms, a switchblade is a knife featuring a blade that springs out of the handle when a button is pressed. But when the knife is being closed, tension from an inner spring is put on the blade. When fully closed, the tension is separated from the knife by a button or switch . When the button is pressed, the tension of the spring is released back onto the blade and it flicks open without any effort.

There are generally two types of automatic knives, the folder, and the OTF (Out The Front). The folder design is only a slight departure from a standard folding knife in that it adds a spring to force the blade into the open position as soon as the button or switch holding the blade in place is released.  The OTF knife, however, is an almost universally automatic design in which the blade slides forward and backward to deploy and close the blade, much like a pen opens and closes.

How an Assisted Opening Knife Works

An assisted opening knife, sometimes called a spring-assisted knife, is a knife that springs open only after the blade is slightly pushed open with force.

Unlike the automatic design, nothing holds down the assisted opening knifes blade when it's in the closed position. As the user begins opening up the blade with a thumb stud or flipper lever, which has some resistance, the spring or torsion bar catches the knife and propels it open where it locks into place.