Everything You Need to Know About Gravity Knives

Gravity Knife” – the term invokes a sense of danger, shrouded in a mist of legal ambiguity. Are gravity knives really dangerous? What even is a gravity knife? Are they as illegal as most people think? The answers might just surprise you.

What is a gravity knife?

For the purposes of this article, a gravity knife is a knife that opens by the force of gravity. Usually, the blade is held closed by some mechanism in the handle that must be disengaged, and once it is, the blade swings free.

If you ask federal law what a gravity knife is, it will say any knife that opens “by operation of inertia, gravity, or both.” Legally, gravity knives are classified as switchblades. As a knife nerd and not a lawyer, I differentiate. In my mind, “switchblade” implies a spring-loaded opening mechanism, and gravity knives don’t have springs.

History of Gravity Knives

In WWII, Luftwaffe pilots wanted a knife that was compact to carry, had a good-sized blade, and could be opened with one hand. Such a knife would be useful in cutting a pilot out of a parachute. Up to that point, knives were either fixed blades (one-hand operable, good size) or slip joint or friction folders (compact carry, good size). The locking mechanisms we know and love were still decades out and ball bearings hadn’t made their way into knives yet.

The solution was the gravity knife. The user would actuate a lever with his or her thumb, aim the blade downward, and gravity would pull it out. Once the user released the lever, the knife was locked open. Do the entire process in reverse, and the knife is closed! As an added perk, the user’s fingers never crossed the path of the blade, so they were among the safest knives of their time.

With strong military roots, gravity knives became synonymous with war, which was already synonymous with weapons. Later, as with virtually every other instrument of war, Uncle Sam had something to say about it, and as with every other time Uncle Sam had something to say, people started looking for loopholes. It is via those loopholes gravity knives MIGHT be legal for you. More on that later.

How Do Gravity Knives Work?

Gravity knives come in all shapes, sizes, and mechanisms, but they all have one thing in common: you don’t have to touch any part of the blade to open one. The Paragon Warlock gravity knife is the most popular gravity knife we sell. To open it, you pinch the pivot together, separating the two clam-shell style handle scales. From there, the blade can swing free. To lock open, just release the handles.

Paragon Warlock Gravity Knife

The Reate EXO is another popular gravity knife. It operates by gripping the handle scales and letting the frame drop out. From there, the blade slides out with gravity.

Reate EXO Gravity Knife
Video Credit – Logan Smith @SoakedInSunlight

In both of these cases, and with any knife, they are no more dangerous than their user wants them to be.

Are Gravity Knives Legal?

Oh boy. I knew this one was coming. Buckle up, it’s a wild ride.

The legal definition of “gravity knife” (discussed earlier) is exactly seven words long. And not seven authoritative and definitive words, seven vague words. It is described as any knife that opens automatically

“by operation of inertia, gravity, or both.”

This painfully nonspecific definition uses two words right out of physics class. That sounds like a job for Science Maya!

“Gravity,” she said, “is a universal force which attracts two objects of mass together. In a knife, that means Earth’s gravity is doing all the work, not you.

“Inertia, on the other hand, is the nature of an object to remain in its current state of motion unless acted on by an outside force. In a knife, this translates to flicking your wrist, and the momentum of the blade carries it open.”

So, long story short, a knife that you can drop or wrist flick open can be called a gravity knife, but if there’s a mechanism like a clamshell to open, it’s not? I think?

According to the legal definition, the Paragon Warlock isn’t a gravity knife. The Luftwaffe Gravity Knife isn’t even a gravity knife! But I can wrist flick the Benchmade Freek in my pocket. Do I have a Benchmade gravity knife? No? Maybe?

Opening a Benchmade Freek using only gravity and inertia. Is it a gravity knife???

The broad and non-specific definition of “gravity knife” has led to inconsistent enforcement of the law. Some self-proclaimed gravity knives are not gravity knives, and some you’d never suspect might be. This has caused many headaches for our customer service department.

And all this comes on top of the legal ambiguity surrounding other “switchblades”! Check out our Switchblade Legality Article to learn more on that.

Long story short, gravity knife legality is a gray area. Before you buy a knife that could potentially be a gravity knife, consult a real lawyer, not some knife retailer on the internet.

Conclusion

From their storied past and bizarre present mixed with their unique mechanisms and relative rarity, gravity knives have become some of the most interesting blades out there. Are they inherently dangerous? No more than any other knife. Is owning one a legally complicated subject? Absolutely! But are they cool nonetheless? We sure think so!