A Quick Guide to Double Action Out-the-Front Automatic Knives
A double action out-the-front knife, as its name indicates, is an automatic knife with a blade that comes out of the front of the handle, and a thumb stud that can be pushed or pulled to release or retract the knife respectively. A single action out the front knife basically operates the same way, but only in terms of the blade extending automatically; retraction is manual.
The knife blade is locked into place by a spring-operated restraining pin that goes into a groove in the blade. The two spring carriers fill the spaces on the slide and this settles on the side of the blade. The right spring carrier is held by a tab that fits over the end of the blade. The other spring carrier, thumb stud and slide are held to the right by tension on the main spring.
When the thumb stud is pushed forward, this frees the left spring carrier and the slide. Tension then increases on the main string with the blade and right spring carrier locked. Impinging on the lower pin is a ramp on the slide. As the pin escapes the notch, the blade and right spring carrier can now move. The right spring carrier can only advance a little before stopping in the slide. Momentum brings the blade further prior to flanges delaying its movement. There's another restraining pin that fits into a groove and locks the microtech troodon blade in the stretched out position.
Into another groove in the blade goes a tab on the left spring carrier which restrains it. This means tension in the main spring can be increased by a reverse force on the thumb stud, prior to the upper restraining pin releasing, and the blade and carrier returning to their closed position. Read about pocketknives here at http://en.wikipedia.org/wiki/Pocket_knife.
There is a tiny restraining pin which is the only thing that holds the blade open, and it is vulnerable to failure when abused. The entire slide assembly moves over a minimal distance which is exactly the distance covered by the thumb stud when it moves. The force which allows the blade to be extended or retracted is equivalent to the force that the user exerts when pushing on the thumb stud in order to stretch the main spring before release. Because of this, the microtech ultratech for sale blade's tip is not likely to even make a cut on skin, much less cause significant injury, when it is released. Any object on the blade's path as it is extended can be stopped before it can gets locked in place. There are two easy solutions to this: pull the blade so that it will lock, or push it back inside until it's locked, and then deploy it one more time.
