Switchblades and assisted knives, although seemingly the same, are actually quite dissimilar.
A switch blade (also well-known as an automatic knife) is family of knives with a sliding or folding blade that is released mechanically by springs or centrifugal force when a lever is pressed on the handle. Made popular by films in the fifties like The Wild One and Rebel Without a Cause, switch blades were shortly after prohibited by the US government in 1958. Today, automatic knives are restricted only to military or law enforcement use in most places.
That said, while switchblades are illegal to carry in public, the assisted knife is perfectly lawful for everyday carry in virtually all states. While legal status is the most obvious difference between automatic and assisted knives, they do differentiate in a few other ways.
First, a switch blade knife can fall into one of two categories, there are out the top or out the side opening. An out the side blade is automatically opened when the owner pushes a button on the handle while an out the top knife has a button on the side of the grip that releases the blade. An out the front knife usually has a blade that is sharpened on all sides thus making its primary use as a dagger.
With a switchblade knife the blade is held in place by a lock and is automatically deployed when the trigger mechanism is pushed. The spring that drives the knife open is always under tension and is only discharged when the trigger mechanism which is usually a button on the side of the knife is pressed. As soon as the trigger button is activated the blade will automatically discharge and snap into position. Likewise, to close the blade the switch is pressed again and a second spring pulls the blade back into the grip. This results in tension once again on the first spring and locks the blade into the retracted position.
Virtually all of the restrictions relating automatic knives came into effect during the fifties when movies depicting gangsters enhanced the popularity of this style of knife. After that kids on the street starting getting their hands on them and switchblades got linked with gangs and law-breaking hence the interference of the government to make them criminal.
An assisted knife differs from an automatic knife in that it demands the owner to apply a starting force to open the blade before it automatically opens. The blade in an assisted opening knife is normally held in place by one or two contortion bars. When the owner unfolds the blade manually by a certain amount, normally in the range of ten to forty degrees the assisted mechanism jumps in and proceeds to extend the knife completely.
Unlike switch blades, assisted opening knives are not criminal. They accomplish this condition because as an automatic knife releases only by the pushing of a button an assisted knife does require that the owner employ force to open the blade. Assisted opening knives are most commonly single edge blades and are available in either a straight or serrated edge fashion. They are not commonly believed to be daggers and are instead classed as survival, tactical or everyday carry knives.
If thinking of buying a knife it is invariably prudent to firstly consider what its designated purpose is. Due to its prohibited status, a switch blade is better functioned as a collectable instead than for functional or defensive use. Assisted knives, on the other hand, are legal, safe and highly recommended for everyday carry and defensive use.