How to Choose The Right Kind of Screws

Guest Post by Scott Huntington

August 3, 2020

If you’re new to the DIY world, or simply new to your given project, you might be at a bit of a loss for what screws are best for your build of choice. There are so many to choose from, so it makes sense that you might be dealing with a bit of confusion. The choice used to be a bit more simple: slotted or Phillips. With the expansion of the market, there are more options than ever, which means that you have a whole aisle to stroll through.

Different screws will work differently for whatever project you have on hand, and while you can go a bit more basic, with a bit of research you can probably find something that perfectly fits your needs. Whether you’re working outdoors, using unconventional materials or simply going at a new DIY, the perfect tools exist for you.

The Material

The most important question to ask yourself when picking the materials for your screws is whether you are working indoors or outdoors. If you’re working indoors, you can use zinc galvanized screws, or other screws that are coated to match the aesthetic of your given project. These are generally less expensive, as they don’t have to withstand the elements. However, if you happen to be working on an outdoor project, you might need to pay a bit closer attention to the elemental situation.

For outdoor projects, you need to control for temperature and moisture fluctuation. For this, there are screws that have been put through an extra process of passivation which improves the resistance of the zinc coating. For extreme conditions solutions materials like silicon bronze or stainless steel usually work best.

Other coatings can be added to screws such as black japanning for appearances, or ceramics for friction-reducing.

Screws vs. Bolts

While both screws and bolts are fastener devices, there is a difference between the two. A screw is a fastener that is externally threaded. It has a head at one end, and at the other end it has a helical thread, designed to screw into a hole or directly into material. Screws can come with a pointed or even drill shaped end to help them pierce through surfaces.

This is different from a bolt, which is another externally threaded fastener with a head on one end as well. Bolts go through pre-drilled holes that are already made and have a nut to hold them in place. Bolts may offer more strength and sturdiness for larger projects, as they are relying on the strength of the bolt and nut rather than the pullout strength of the material.

In both cases a washer can be added to spread the load onto surface of the material.

The Head and Drive

The type of head you choose for your screw will depend on the type of project as well as the joint itself that you’re fastening. The head is chosen for is appearance, load spreading capability and drive.

Your tools may also play a role in the process, as a hand held screw driver often works best with Phillips head and straight screws, whereas drills can offer a bit more flexibility.

When it comes to tailoring your screws to your specific projects, materials and joints, there are many choices available to find what fits best.

• Straight screws, also known as slotted screws, are great for simple joints like electrical outlets. They work well with simple screwdrivers and are relatively easy to use.
• Phillips head screws are perfect for woodworking, drywall applications and even electrical appliances. They’re strong enough to hold moderate joints in a variety of materials and work well with simple screw drivers.
• Robertson screws are screws with square heads, great for drilling and higher intensity projects in need of a bit more strength.
• Quadrex screws are a combination of the Robertson and the Phillips head screws. They can pack a lot of power, and are perfect for driving intense projects like framing, deck building and other structural projects.
• Torx screws, also known as star drive heads, provide a minimum amount of wear to the surface, making it a great option for drilling materials you want to preserve as carefully as possible. They’re strong and sturdy, often used in heavy manufacturing and security. Torx screws are often used in the automobile industry as they are good for applying precise amounts of torque when fitted.

While there are even more types of screws to choose from, you can explore the basics and beyond to find what works for you and your project. You may very well mix and match screws within the same project if different structures and joints have different needs.

The Thread

A screw may have a full thread along its length or a partial thread with a straight shank. The straight shank performs two purposes. Firstly it helps with pulling the two pieces together, this is because it slides through the second piece. The second is that it reduced the amount of torque required to fit the screw so can reduce breakages. This is particularly important in harder materials or with long thin screws. These screws are common when woodworking. When fixing sheet metal or drywall a fully threaded screw can be used.

Another key difference in drywall screws is the size and shape of the thread. The drywall screw has a coarse and wider thread than a wood screw. This allows it to pass through the plaster based material without damaging it. Similar these wider threads are advantageous when used with chipboard.

Most screws have a single thread running around their shank. Multi-start or twin thread screws have a second thread intertwined with the first. These are used for hard materials such as hardwood or even concrete. The second thread means the screw has more holding power and uses less torque to be driven into the wood.

The Size

While there are many sizes and materials that can help determine what screw you want for your project, there are a few general rules of thumb to go by. If your project has any kind of instructions, it’s always best to follow them as closely as possible when it comes to choosing a screw size, however, this doesn’t help those building from scratch.

In general, screws should be at least three times the length of whatever material you’re adhering. For example, if you’re screwing a piece of metal into a surface and the metal is an inch thick, your screw should be at least three inches long so it can properly hold your project together. In terms of thickness — or gauge — screws come in sizes two through 16. While eight is the standard, higher gauges like 10 or above can work with heavier duty materials, while lower gauges can usually handle lighter projects.

Get Working

While there are a lot of options when it comes to screws, they all exist for a reason. The perfect screw for your project is out there, and with a little research and elbow grease, you can build the project of your dreams.

About the author

Scott Huntington is a writer who lives in Vermont and loves all things DIY. You can find him outside no matter how cold it gets. 

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  Posted in: Guest Tags: fasteners, screws