A split 16:9 graphic comparing the legality of plastic knuckles in different countries. The left green side shows a black plastic knuckle labeled ‘Canada – Legal,’ while the right red side shows a gold metal-style knuckle labeled ‘USA, Australia, UK – Illegal.’

Thinking of 3D Printing Brass Knuckles? Read This Before You Do!

December 09, 2025•3 min read

3D printing brass knuckles might feel like a cool weekend project — but legally, it’s a minefield. In the USA, several states fully ban them; others restrict carrying or manufacturing. Canada allows plastic knuckles (even 3D-printed ones) but bans metal versions and still punishes misuse. Australia and the UK ban brass knuckles entirely, no exceptions. Penalties range from fines to jail, and “because it’s plastic” doesn’t save you. If you’re considering printing a pair, read the laws first — the consequences aren’t worth the print time.

Introduction

3D printers have unlocked a wild world of DIY creativity — from phone stands to drone parts to fully functional tools. But sometimes people push the limits and think, “Hey, what if I just print brass knuckles?” On paper, it sounds harmless. It’s just plastic, right? But in the eyes of the law, you might as well be holding the real thing.

Before you download that STL file, here’s what you need to know based on actual legal summaries and weapon regulations from Canada, the USA, Australia, and the UK.

The Legal Reality (And Why 3D Printing Doesn’t Make It Safer)

In almost every country, brass knuckles are treated purely for what they are: weapons designed to injure, not tools. That means the material doesn’t matter. Whether you machine them out of steel or print them in ABS, the classification is often the same. And yes, the law considers 3D printing as “manufacturing” — which is exactly where many people accidentally step into criminal territory.

USA: A Patchwork of Laws

The United States is tricky because every state has its own rules. Some states — like California, New York, and Texas— completely ban owning, selling, or even printing brass knuckles. Other states might allow possession but ban concealed carry. And then there’s federal law, which can still punish weapon manufacturing if it falls under restricted categories.

So in the USA, printing them is often a gamble unless you’ve checked your exact state laws.

Canada: Surprisingly Specific

Canada draws a hard line between metal and non-metal knuckles.

Metal = illegal, no exceptions.
Plastic = legal to own.

The Canada Border Services Agency even lists plastic knuckles (ABS, carbon fiber, etc.) as allowed items. But here’s the catch: if you carry them, display them as a weapon, or use them to intimidate someone, you can still get charged under other criminal laws. So yes, you can print them — but you definitely shouldn’t walk around with them.

Australia: Zero Tolerance

In Australia, brass knuckles are universally classified as prohibited offensive weapons. That includes 3D-printed versions, metal versions, display versions — everything. You need explicit police authorization to have them, and printing them without permission is treated the same as buying or importing them.

In short: printing them in Australia is a guaranteed legal problem.

United Kingdom: Completely Illegal

The UK doesn’t play around with offensive weapons. Brass knuckles are banned across the board — owning, selling, buying, or manufacturing, including 3D printing. Even having them in your home can be enough to trigger penalties if authorities consider intent. Possession in public? Expect arrest.

The UK is the strictest of all four regions.

So… Does “It’s Just Plastic” Save You?

Not really. Most countries judge knuckles by their purpose, not their strength. Even in Canada, where plastic versions are technically allowed, carrying them for self-defense can still land you in trouble .

If your goal is personal safety, there are much safer and legal alternatives: tactical flashlights, alarms, pepper spray (legal in some regions), or simply proper self-defense training.

Final Thoughts

3D printing brass knuckles isn’t just a “fun print.” Depending on where you live, it can be an actual criminal offense. The laws are strict because these items are designed for harm, and 3D printing doesn’t create a loophole. Before you fire up your printer, make sure you understand the legal consequences — one small print can lead to a very big problem.

Citations

[1] Monkey Knuckles Canada – Brass Knuckles Legal Guide
[2] U.S. State Weapon Regulation Summaries
[3] Australian Offensive Weapons Laws
[4] UK Offensive Weapons Act Guidance
[11] Canadian CBSA Material-Based Weapon Classification Guidelines

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