Dual Action OTF Automatic - Automatic Opening Systems
Dual Action OTF Automatic Info
Dual Action OTF's are often considered the darling of the Automatic knife industry. Usually the most expensive, and certainly the most cost prohibitive to produce, dual action OTFs (or D/A OTFs) are difficult to build to exacting standards demanded by the high end knife consumer. The mechanics of an dual action OTF can be a bit more finnicky than a single Action OTF, and while they do not fire quite as hard as the Single Action ones, they make up for it with the ability to close at the slide of a switch.
Sometimes Dual Action is used to describe side openers, which refers to the ability to open the knife manually as well as automatically. This can be confusing as with referring to OTF automatics, the D/A designation refers to its ability to open and close the knife using the automatic switch.
How it Works
I have personally handled two different types of D/A OTF Automatic. The first kind is the mechanism that Microtech and most others use, and it uses a spring to launch the blade into the locked position. While the blade is traveling forward, there is no constant pressure on the blade, so if you were to fire it into a peice of paper, the blade would stop and become slack, requiring you to manually pull the blade forward to lock it into place. The second kind I have handled is the type used by Jeff Harkins on his Triton Automatics. I believe this type does have constant spring tension so when you fire it, it will keep going through the peice of paper. Either that or it has a very powerful spring that a peice of paper will not stop. I have not handled the Sandshark D/A OTFs, so I cannot comment on those.
The blade usually has two pins in the tang, and they ride on guides, and the in and out action of the blade is controlled by two springs. When the knife is fired, one spring is released, while one is compressed, which is why there is a fair bit of resistance when you fire a D/A Automatic.