The cocking arm (blue) emerges through the base of the handle friction with the handle holds it in place. 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. 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. Schematic of single action out the front automatic knifeĪ single action out the front knife operates under similar principles but will only automatically extend the blade which must then be manually retracted. 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. This is easily remedied by either pulling the blade out so that it locks or pushing it in till it locks and then redeploying.ĭouble-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. Any object in the path of the extending blade may cause the blade to stop before it can lock in position. 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. 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. The whole slide assembly moves only a short distance, exactly as far as the thumb stud moves. The small restraining pin at 3 is the only thing holding the blade open and is prone to failure if abused. 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. A tab on the left spring carrier fits into a hole in the blade at position 4 which restrains the left spring carrier. Momentum carries the blade further before flanges (not shown) retard its motion.Īnother restraining pin at position 3 fits into a notch and locks the blade in the extended position. The right spring carrier moves only a short distance before it comes to rest in the slide. When the pin evacuates the notch, the blade and right spring carrier are free to move. A ramp on the slide impinges on the lower pin. This increases tension on the main spring as the blade and right spring carrier are locked. When the thumb stud is pushed forward the slide and left spring carrier are free to travel. Tension on the main spring (red zig-zag) holds the other spring carrier, slide and thumb stud (light grey) to the right. The right spring carrier is restrained by a tab at position 2 that fits over the end of the blade. The two spring carriers (green) fit into the spaces on the slide (blue) and this assembly rests to the side of the blade. 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. Schematic of double action out the front automatic knifeĪ 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. Congress banning the manufacture and sale of switchblades, beginning a wave of legal restrictions worldwide and a consequent decline in their popularity. Delaney of New York authored the first bill submitted to the U.S. It is unlocked by a mechanism that allows the blade to be folded and locked in the closed position.ĭuring the 1950s, US newspapers as well as the tabloid press promoted the image of a new violent crime wave caused by young male delinquents with a stiletto, switchblade, or flick knife, based mostly on anecdotal evidence. Virtually all switchblades incorporate a locking blade, where the blade is locked against accidental closure when the blade is in the open position. A switchblade (also known as switch knife, automatic knife, pushbutton knife, ejector knife, flick knife, Stiletto, flick blade, or spring knife ( Sprenger, Springer )) 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.
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