Assisted Opening Knives

Comparing an AO knife to a switchblade

Although you may think an assisted opening knife (often called an AO knife) is the same as a switchblade, they are in fact quite different. A switchblade is seen as an “automatic opening” knife and are considered illegal in the United States. A switchblade is opened via a spring that is released with a button on the handle. Regardless of the fact they were romanticized in the 1950s, they were outlawed by the 1958 US Switchblade Act. Even most police and military organizations have moved away from true “automatic” knives and towards the “assisted” opening knife.

Under the 1958 law, a switchblade is illegal to carry – but not an assisted opening knife. Beyond their legal differences, the way an assisted opening knife works is very different. Switchblades fall into one of two categories: out the front and out the side. The switchblade blade itself is usually double sided, whereas an AO knife is blunt on one side and only opens via the side.

Further, as previously mentioned, a switchblade has a trigger release button that opens the blade through an “always on” spring. This means the blade releases (fully) the moment the release button is pressed. An assisted opening knife only has a button that is designed to start the blade opening from the handle. The user is required to complete the motion of opening the knife. The blade itself is not under constant tension like a switchblade and is held in place by one or possibly two contortion bars. Therefore, an AO knife do not pop open like a switchblade. Instead, an AO blade opens about 45 degrees by the user before the internal mechanism finishes the opening process.

Portrayed in films of the time, switchblades became quite popular. They were soon associated with street crime and gangs and were quickly outlawed. Assisted opening knives on the other hand are legal to own and carry in the United States and Canada. They are particularly popular with outdoorsmen and “first responders” like police and fire fighters, although an assisted opening knife can also be used for self defense.

Considerations to keeping your Assisted Opening Knife rust-free

  1. Stainless steel does NOT mean “never rust”. Although your assisted opening knife may have a stainless steel blade, it still contains carbon which can rust.
  2. The best way to reduce the possibility of rust on the blade is to make sure you dry the blade whenever it gets wet. Moisture is the cause of rust on metal. This is especially important before you store your knife for extended periods between use.
  3. Lastly, the best long term insurance for a rust-proof and corrosion-proof knife is to keep alight coat of oil on the blade.

Remember, all other metal parts of your knife are also susceptible to rust – be sure to care for the entire knife – not just the obvious blade.