Spanner Screws

If you're looking to give your construction project some added security, nothing beats spanner screws. Their two-holed design makes them difficult to remove without the proper tools. If you're focused on some of the finer details of your project, spanner screws offer a unique appearance that will look great and protect your final result.

In this guide, we'll discuss what spanner screws are, how you can use them and the different types available for use.

What Are Spanner Screws?

Spanner screws are a type of tamper-resistant fastener, meant to make it more difficult for a thief or vandal to remove them. Like most security screws, spanner screws have a unique shape that requires a special kind of driver to remove. A spanner screw has a head with two holes. Because of the distinct shape, spanner screws are often called "snake eye" or "pig nose" screws. They also have a few variations, including the three-hole spanner screw and the slotted spanner screw.

The screw can be installed and removed using a matching spanner drill bit. A spanner drill bit has two small pins protruding from it, both with square tips. A spanner drill bit is more delicate than other drill bits because of the small diameter of the pins. To avoid breaking a spanner drill bit, always insert a spanner screw head-on. Make sure the screw head sits flush against the surface — drilling in further can break the drill bit.

While spanner drill bits and drivers are less common than a Phillips or flathead screwdriver, they are still commercially available. So, while they are hard to come by in an everyday toolbox, you can usually get them from a specialty vendor. 

Spanner Screw Applications

The most common use for a spanner screw is to prevent unwanted removal. Two-holed spanner screws make a great deterrent for theft and vandalism. The tool is uncommon enough to secure public places. Some manufacturers find spanner screws' minimalist design more attractive than standard Phillips head or Flathead screws. 

So, many design-forward products use spanner screws on their exterior-facing surfaces. Spanner screws are commonly used in:

  • Schools: Universities and public schools can all benefit from spanner screws throughout their properties. Students are doubtful to have specialty screwdrivers lying around at home. Schools can use spanner screws in bathrooms, playgrounds and furniture across their campuses.
  • Public restrooms: A common concern for public toilets is vandalism. We've all seen graffiti and scratches on stall doors. Some vandals will go so far as to take off the door or hardware. With the specialized driver needed to remove spanner screws, you can decrease the likelihood of tampering.
  • Municipal property: Outdoor property, such as benches, playground equipment, utility hole covers and street signs, is a frequent target for tampering. Spanner screws are a popular solution. You can even find spanner screws holding up the famed signs for the London Underground.
  • License plates: The plates on your car can be a hot-ticket item for petty criminals. Spanner screws can keep your plates secure, while also adding a nice detail to an attractive sports car. 
  • Specialized equipment: With some digging, you can probably find spanner screws on a few of your household appliances or electronics. They're just as prevalent on industrial equipment that requires special maintenance. Often, these screws fit right into the minimalist product design of most gadgets. They also serve to prevent some DIY and third-party repairs. They protect a product's warranty and avoid the damage that can occur from inexperienced repairs.
  • Museum exhibit cases:The National Parks Service has recommended tamper-resistant screws in museum exhibits since 1995. With specialized spanner screws, museums can protect artifacts while still gaining access to cases for maintenance. These screws can fasten doors as well as control panels attached to displays.
  • Scaffolding: In construction, unauthorized tampering can cause scaffolding to become unstable. When keeping screws in place is a matter of safety on job sites, spanner screws can save lives.

Spanner Head Screws

"Spanner" refers to the unusual shape of the screw head used. Even among spanner screws, however, there are a few variations in shape:

  • Two-hole: The most popular form of spanner screw is a two-hole screw head. Their shape has garnered nicknames such as "snake eyes" and "pig nose" screws. They have two rounded pinholes on the head and use a drill bit insert with two protruding pins.
  • Three-hole: Another variety of the spanner screw has three holes rather than two. A three-hole screw head has three rounded pinholes arranged in the points of a triangle. They require a specialized drill bit with three prongs.
  • Slotted: You can also find spanner screws that feature two slots rather than rounded holes. These screws look like the standard Flathead screw with a bar through the middle.

At FMW Fasteners, we carry two kinds of spanner head screws. Both are the two-hole variety:

  • Flat head: A flat head screw is the most common form of a countersunk screw. After installation, it will sit flush against the surface. It's common for use in woodworking since the head won't protrude from the wood.
  • Pan head: A pan head screw is the most common form of round head screw. Pan head screws are popular in machinery.

Spanner Security Screws

Like all forms of tamper-resistant screws, spanner screws increase security. Since spanner screw drill bits and screwdrivers are commercially available, they aren't a catch-all for tamper and theft prevention. Still, their relative rarity keeps them out of the hands of casual vandals. If you want to make your spanner screws even more secure, several practices can help, including:

  • Using multiple types of security screws: By using another shaped screw head alongside your spanner screws, you can dramatically increase your security. First, it decreases the likelihood that a thief or vandal will have the proper tools. Second, it increases the time it takes to unscrew something. The longer it takes to remove the screws, the higher the chances of being caught, which deters tampering.
  • Ensuring screw heads are flush: With some difficulty, tamper-resistant spanner screws can be removed with a pair of pliers. To prevent this, make sure to install screws flush against their surface. If you can, use a recessed design to make it harder for someone to grip the screw head with pliers.

  • Securing specialized drill bits: After you install your spanner screws, treat the drill bit like you would any other key. Keep the drill bit somewhere it won't be easily discovered, and secure it if possible.
  • Using a screw with fine threads: Another way to increase security is to use tighter screw threads. While thicker threads can be worked through a piece of wood quickly, finer threads take more time. Anything that lengthens the removal process will deter tampering, thanks to the increased risk of being caught.

Shop Our Collection of Spanner Screws

No matter what kind of screw your project needs, FMW Fastener's collection of spanner screws will help you increase your security. Whether you need self-starting pointed screws or flat-bottomed machine screws, you'll find exactly what you need. We also have a collection of metric spanner screws to cover all your bases in any measurement.

We specialize in hard-to-find parts and let you order in any quantity. Whether you need spanner screws for a large manufacturing job or to bump up the security on one of your home projects, you'll find great prices and fast shipping. We also offer 100% hassle-free returns on any order and free shipping on any order over $100. Start shopping today!


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