What’s An Automatic Knife? Are They Illegal?

You’ve probably seen the Italian Stiletto switchblade being wielded by a bad guy in a Hollywood film. The Stiletto is an Automatic Knife, a type of spring-loaded pocket knife that was criminalized by newspapers in the 1950s. Congress even sought to restrict their manufacture and sale with the Federal Switchblade act in 1958.

This guide is not legal advice. Purchase and possess an automatic knife at your own risk.

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How an Automatic Knife Works

The blade in an automatic knife is under constant spring tension, with a lock keeping the blade held inside the handle. When the blade’s button is pushed, the lock disengages and the blade opens in the blink of an eye. Automatic knives either open from the side of the handle, or out the front of the handle (“OTF”).

How a Side-Opener Works

In a side-opening auto knife, one side of the blade rests against a spring. The spring is compressed when the blade is closed. The spring’s tension is always pushing against the side of the blade, ready to force it out of the handle into the open position. The blade and spring are held in place by a plunger. When the knife’s button is pressed, the plunger disengages, allowing the blade to to be pushed open by the spring, releasing its tension. Closing the blade recompresses the spring, making it ready for the next release.

How an OTF Knife Works

OTF knives are single-action or double-action. Like a side-opener, the single-action OTF blade is held inside the handle by a plunger, with a compressed spring resting against the bottom of the blade. When the blade’s button is pressed, the plunger releases the blade, and the spring’s tension forces the blade out the front of the handle.

Double-action OTF knives can be opened and closed automatically, without the user having to manually close the blade to recompress its spring. Instead, the blade slides on a rail, with a spring that is tensioned by the user pressing on two-way push mechanism. When the user presses the mechanism forward, tension builds in the spring by stretching it, until the mechanism releases a plunger.

Once the plunger is disengaged, the stretched spring snaps forward and releases its tension, pulling the blade and launching it out of the handle. To close the knife automatically, the same mechanism works in reverse, creating spring tension until the plunger disengages and snaps the blade back into the handle.

Are Switchblades and Automatic Knives the Same?

Sometimes. All automatic knives are switchblades, but not all switchblades are automatic. For any knife to be considered automatic, its blade must open with spring force when the user pushes a button or releases a lock of some kind.

Gravity knives and butterfly knives open when a lock, button, or lever is released, but there is no spring forcing the blade open. Gravity either causes the blade to fall out of the handle, or the user must physically manipulate the blade. Knives like these are considered switchblades, but they aren’t automatic.

Not All Spring-Assisted Blades are Automatic

Some spring-assisted folding knives are incorrectly called switchblades or auto knives. If a spring-assisted knife requires the user to physically open the blade (either by pressing on the spine, or by flicking the blade open via a thumb stud) then it is neither a switchblade nor an automatic knife.

SOG Flare Folder

The SOG Flare Folding Knife is a great example of this not-a-switchblade. A small piece of curved spring steel in the handle keeps the blade pressed inside, preventing accidental release. The user must press on the thumb stud to overcome the spring tension. Once the tension is overcome by the user, the spring steel will reverse the direction of its curve, applying tension against the blade in the open position.

Are Automatic Knives Illegal?

Under federal law, auto knives and switchblades are legal in the U.S. The Federal Switchblade Act only outlaws the possession of switchblades and automatic knives on Native American reservations and territories including Puerto Rico, Guam, the U.S. Virgin Islands, the American Samoa, the Northern Marianas, and on Navy vessels and government aircraft.

How The Law Defines Switchblades

The official text of the Switchblade Act (U.S.C. Title 15, Chapter 29) defines a switchblade as any knife with, “A blade that opens automatically, either by pressure on a button or other device, or operation of inertia, gravity, or both.”

Exceptions to the definition include, “A knife that contains a spring, detent, or other mechanism designed to create a bias toward closure of the blade and that requires exertion applied to the blade by hand, wrist, or arm to overcome the bias toward closure to assist in opening the knife.”

Basically, that last part means spring-assisted knives like the SOG Flare are legally not considered switchblades under federal law.

Some States Have Banned Auto Knives

This list can change at any time. Always check your local and state laws before possessing an automatic knife or switchblade.

The following states have total bans on automatic knives:

  • Delaware
  • Minnesota
  • New Jersey
  • New Mexico
  • *Pennsylvania (HB 1929 passed; ban expires January 2, 2023)

The following states have placed restrictions on automatic knives:

  • California: Blade must be less than 2″ in length.
  • Colorado: Concealed blades cannot measure more than 3.5″ in length.
  • Connecticut: Blade cannot measure more than 1.5″ in length.
  • Illinois: Can only be possessed with a valid Firearms Owner’s ID Card.
  • Maryland: Legal, but concealed carry is prohibited.
  • Massachusetts: Blade cannot measure more than 1.5″ in length.
  • New York: Can only be possessed by law enforcement or while hunting, trapping, or fishing with a valid license.
  • North Carolina: Legal, but concealed carry is prohibited.
  • North Dakota: Blade cannot measure more than 5″ in length.
  • Vermont: Blade must be less than 3″ in length.
  • Washington: Can only be possessed by law enforcement and emergency personnel.
  • West Virginia: Must be 21 years of age to possess.

The American Knife & Tool Institute has a great resource for keeping up on automatic knife state laws. Click here to view it.