Blade deployment systems

Folding knives on the market these days are far more creative than those of yesteryear. One of the greatest differences in modern day knives is in the system by which the knife blade is deployed. There are at least six broad categories by which a knife blade is deployed in todays knives. While there certanly are others, these are the six main systems.
The nail nick is by far the oldest form of folding knife deployment system. Here a small crevice of steel has been cut out from the knife blade, just large enough to fit a thumb nail into and pry outward. Traditional pocket knives have used this system for years. It is low tech, easily incorporated into the knife, inexpensive and effective. Although this is the functional equivalent of a car without power options, the end result is the same as the fancier tricked out knife. The blade will be open and ready for use.

Another long standing blade deployment system is that of the automatic knife. Known by most as a switchblade, the automatic knife will deploy the blade with force upon the triggering of some trip system, often a button but also taking the form of sliding or squeezing of the scales, pushing a slide button or depressing a finger button. These knives contain springs that are under tension while closed and release their energy when tripped, thus propeling the blade from the handle into an open state. Automatic knives have been demonized through Hollywood and labled nefarious thus resulting in their ban many years ago. This ban is more cosmetic than anything else as a plethora of knives exist on the market legally whose blades open just as fast if not faster. These knives come in two general varieties which would be switchblade style or out the front (OTF). The switchblade style is commonly recognized, however the OTF design hides the blade within the handle and deploys in a straight line outward until meeting a stop at which point the blade locks open.

Currently, one of the most popular blade deployment systems is the thumb stud. This again is a low tech but effective method in which a small post or even blade cutout is used as a grip point for the thumb and when pushed forward in a rotating manner, deployes the blade fully. Spyderco invented the thumb hole which follows this same process. Other knifemakers such as Gerber Knives and Emerson Knives often use the blade stud.

The cam system of opening a knife is less common, but is especially appreciated for its creativity and when well executed is an exciting addition to any knife. One of the well known knives in recent memory to use the cam system is the Camillus Cuda. By pushing forward on a circular thumb plate on the handle of the knife, the base of the blade is rotated in a semi-circle, thus opening the full blade length. A more creative and complicated system can be found on the Kershaw ET, which is too unique to describe however Blade Magazine awarded Kershaw Knives the 2005 Most Innovative American made design of the year for this knife.

Assisted opening folders were intrduced by Ken Onion in collaboration with Kershaw knives. Taking a cue from automatic knives, but limiting the function sufficiently to remain legal, the assisted opening knife blade is manually deployed with a thumb stud approximately 30% of the blade travel. After this point, an internal spring takes over and snaps the blade open under its own power. There are many such knives on the market today.

Finally, the genre of butterfly knives is a Philipino design in which the blade is deployed with a flourish of motion. The blade is maintained inside the split handles which are each hinged to the blade base by a rivet. Each handle half swings around to fully encapsulate the blade and similarly swings to expose the blade.

The various knife blade deployment systems to be had are limited only by imagination. More and more, unique ideas are croppng up to define the best and newest way of putting a cutting tool in your hand fast. Personally I look forward to the further refinements we will see in this area as the continuing evolution of the folding knife develops.

Buck Knives, Benchmade Knives
Kershaw Knives, Cold Steel Knives