A switchblade (also known as switch knife, automatic knife, pushbutton knife, ejector knife, flick knife, gravity knife, flick blade, or spring knife) is a pocketknife with a sliding or pivoting blade contained in the handle which is extended automatically by a spring when a button, lever, or switch on the handle or bolster is activated. Virtually all switchblades incorporate a locking blade, a means of preventing the blade from being accidentally closed while in the open position. An unlocking mechanism must be activated in order to close the blade for storage.
During the 1950s, American newspapers as well as the tabloid press promoted the image of a new violent crime wave caused by young male delinquents with a switchblade or flick knife, based mostly on anecdotal evidence.Levine, Bernard, "Switchblade Legacy", Knife World, August 1990, pp. 27–29 In 1954, Democratic Rep. James J. Delaney of New York authored the first bill submitted to the U.S. Congress banning the manufacture and sale of switchblades, beginning a wave of legal restrictions worldwide and a subsequent decline in their popularity.
Method of operation
Side-opening
The most common type of switchblade is the side-opening or out-the-side (OTS) knife. These resemble traditional manually operated folding knives, but feature a coil or leaf spring which powers a blade that is released when the activation button is pressed. Side-opening knives may feature a safety mechanism that prevents the accidental actuation of the blade release mechanism. Manipulation of a lever, slide button, bolster, or picklock releases the blade for closure.
Out the front (OTF) knives
Double action OTF knives
A double action out the front knife is so-called because the blade emerges from the front of the handle and the thumb stud can be moved forwards or backwards to extend or retract the knife respectively.
The knife blade (dark grey) is locked in position by a spring-loaded restraining pin (yellow and red) fitting into a notch in the blade at position 1. The two spring carriers (green) fit into the spaces on the slide (blue) and this assembly rests to the side of the blade. The right spring carrier is restrained by a tab at position 2 that fits over the end of the blade. Tension on the main spring (red zig-zag) holds the other spring carrier, slide and thumb stud (light grey) to the right.
When the thumb stud is pushed forward the slide and left spring carrier are free to travel. This increases tension on the main spring as the blade and right spring carrier are locked. A ramp on the slide impinges on the lower pin. When the pin evacuates the notch, the blade and right spring carrier are free to move. The right spring carrier moves only a short distance before it comes to rest in the slide. Momentum carries the blade further before flanges (not shown) retard its motion.
Another restraining pin at position 3 fits into a notch and locks the blade in the extended position. A tab on the left spring carrier fits into a hole in the blade at position 4 which restrains the left spring carrier. This allows reverse force on the thumb stud to increase tension in the main spring before the upper restraining pin releases and the blade and carrier can return to the closed position.
The small restraining pin at 3 is the only thing holding the blade open and is prone to failure if abused. The whole slide assembly moves only a short distance, exactly as far as the thumb stud moves. The force that causes the blade to extend or retract is equal to the force applied by the user on the thumb stud to stretch the main spring before it releases. For this reason the tip of the blade is unlikely to even break skin and is entirely incapable of causing significant injury when released though the edge of the blade may still cut as it moves as with any knife. Any object in the path of the extending blade may cause the blade to stop before it can lock in position. This is easily remedied by either pulling the blade out so that it locks or pushing it in till it locks and then redeploying.
Double-action knives have the advantages of being able to automatically retract the blade, as well as allowing the main spring to be in the "at rest" position whenever the knife is fully open or closed. However, because they have more complicated mechanisms, double-action OTFs will tend to be more expensive, have a weaker firing action, and a less-solid lockup than comparable single-action OTFs.
Single action OTF knives
A single action out the front knife operates under similar principles but will only automatically extend the blade which must then be manually retracted.
One spring post (green, left) is rigidly fixed to the handle (orange), the other spring post (green, right) is fastened to the base of the blade. The main spring (red) is under tension, but the blade cannot eject because the spring mounted button (light grey, its spring not shown) is resting in a notch in the blade. The cocking arm (blue) emerges through the base of the handle; friction with the handle holds it in place.
When the button is depressed (sideways into the handle or, as illustrated, into the page) a slot in it aligns with the blade and allows the blade to move forward. When the blade is fully extended flanges on the blade engage pins on the cocking arm retarding the blade's motion. The blade is locked in position when the rear notch of the blade allows the button to return to its rest position. Even if the button is pressed spring tension holds the knife open.
To retract the blade the button is again pressed so that its slot aligns with the blade. The cocking arm is pulled backwards which itself pulls the blade backward. When the blade is fully retracted the spring mounted button rests in the forward notch and again pops up and locks the blade in the cocked position. The cocking arm is then manually pushed forward to again sit flush with the handle.
Because the main spring is constantly acting on the blade and is extended by a far greater amount and is cocked by the whole hand and arm rather than by thumb the force it can exert on the blade is greater than with a double action knife. This allows the tip of the blade to break skin when deployed and possibly penetrate a few millimeters (or hundredths of an inch) past it or to pass through light clothing. While still not a strong design, because it is more firmly attached a quality single action out, the front blade displays less wobble and play than its comparable quality double action counterpart.
Spring-assist knife vis-à-vis switchblade While operationally identical (in terms of one-handed opening), the "spring-assist" or "assisted opening" knife is not a switchblade or automatic knife. A switchblade opens its blade from the handle automatically to the fully locked and open position with the single press of a button, lever, or switch that is remotely mounted in the knife handle or bolster. In contrast, a spring-assist design uses either 1) manual pressure upon a protrusion on the blade itself or 2) movement of a lever or switch directly linked to the blade to initiate partial opening of the blade, at which point an internal spring propels the blade into the fully open, locked position. By this definition, some out-the-front automatics could be considered spring-assisted knives rather than switchblades, and some merchants in the United States sold them as such during periods of switchblade illegality.
Despite this difference in function, the criminal codes of many nations treat the assisted opening knife, like the switchblade, as a prohibited weapon. In the US, persons have occasionally been arrested or prosecuted by state law enforcement authorities for carrying assisted-opening knives defined as an illegal switchblade."UPDATE: Motion for Reargument in NY Assisted-Opener = Switchblade Case Denied", KnifeRights.org, 28 October 2018, retrieved 22 March 2022 "Freddie Gray Falsely Arrested on Illegal Knife Charge – Update on the Freddie Gray Knife Arrest", KnifeRights.org, 1 May 2015, retrieved 28 March 2022 An attempt to criminalize the sale of spring-assisted knives by federal law enforcement was forestalled by a US 2009 amendment (Amendment 1447) to 15 U.S.C. §1244. This amendment provides that the Switchblade Knife Act shall not apply to spring-assist or assisted-opening knives (i.e. knives with closure-biased springs that require physical force applied to the blade to assist in opening the knife).Amendment 1447 to 15 U.S.C. §1244 adds a fifth exception to the definition of a switchblade knife: "Sections 1242 and 1243 of this title shall not apply to: 5) a knife that contains a spring, detent, or other mechanism designed to create a bias toward closure of the blade and that requires exertion applied to the blade by hand, wrist, or arm to overcome the bias toward closure to assist in opening the knife."
Legislation Austria Beginning with the Austrian Arms Act of 1996Waffengesetz (1996): The 1996 version of the Waffengesetz appears to drop the switchblade from the category of prohibited weapons entirely, regardless of blade type: "Gegenüber der bisherigen Rechtslage sind nunmehr Waffen, mit denen ohne Verwendung von Patronen reizauslösende Mittel versprüht werden können, sowie Spring- und Fallmesser nicht mehr der Kategorie der verbotenen Waffen zuzurechnen ... Im Hinblick auf andere ebenso gefährliche Stichwaffen (z.B. Butterflymesser) und die Tatsache, dass Spring- und Fallmesser in den übrigen EU-Mitgliedstaaten keineswegs verboten sind und daher von Touristen und anderen Reisenden, in Unkenntnis des österreichischen Waffengesetzes, mitgebracht werden, ließ es zweckmäßig erscheinen, auch diese Waffen aus der Liste der verbotenen zu streichen." switchblades, like all other knives, are generally legal to buy, import, possess or carry, regardless of blade length or opening or locking mechanism.Waffengesetz (1996) The only exception are minors (defined as persons under the age of 18) and people who have been expressly banned from owning and carrying any weapon (Waffenverbot): both groups may only possess knives which are not considered "weapons" under the Arms Act, defined as "objects that by their very nature are intended to reduce or eliminate the defensive ability of a person through direct impact". Switchblades usually fall under that definition.
In Austria the regulatory laws of individual states and the Assembly Act prohibit switchblades and other knives from being carried into a public building, school, public assembly, or public event.Jell, Sonja (Magistra) "Weapons Law: Knives in Austria"
Australia In Australia, switchblades are banned by the Customs (Prohibited Imports) Regulations as a Prohibited Import. Australian customs refer to the automatic knife or switchblade as a flick knife. Australian law defines a flick knife as a knife that has a blade which opens automatically by gravity, by centrifugal force, or by any pressure applied to a button, spring or device in or attached to the handle of the knife, a definition that would cover not only switchblades and automatic-opening knives, but also gravity knives and balisongs.
At a state and local level, most jurisdictions declare flick knives to be prohibited weapons in their respective acts, codes and regulations. Persons residing in states that do not have specific weapons legislation covering switchblades (such as Tasmania) are still covered by Federal Customs legislation, but in conditions where the state has no legislation against such items, an exemption may be applied for and received if approved by the chief supervisory officer of the police service in that state.