From home repair tasks to intricate DIY projects, choosing the right screw can make a significant difference in the success of your work. You’ve already learned about the different parts of a screw, but how do you decide which screw to use?
This guide will explore the critical factors such as material compatibility, matching the screw bit to the drive, the implications of screw head shape, the importance of choosing the right length, diameter and thread length, and understanding different types of screws.
Screw Selection Guide
The first step in the selection process is the material to which the screw will be implanted. Although many screws can be used for different types of materials, there are some which are specialized for certain materials. The most common materials that screws are used for include but are not limited to the following.
- Plaster & More
Be certain that the screws you purchase are designed to be driven into the material you want to use. Keep in mind that there are screws designed to be driven into specific materials. Such screws are generally made from the following materials.
- Brass: Can corrode, so best used indoors for cabinets.
- Chrome-Plated: Similar to zinc-plated and resists corrosion
- Dichromate: Normally yellow coating that disappears over time
- Galvanized (Zinc-Coated Steel): Quite common with silver appearance. The zinc-coating prevents rust formation.
- Phosphate: Black in color and resists corrosion
- Stainless Steel: Resistant to rust, perfect for outdoor use.
For the most part, wood, chipboard, and lag screws are zinc-coated. While drywall screws are generally phosphate. Stainless steel screws can be for wood, metal, or any materials that is mostly outdoors or exposed to humidity.
Match the Screw Bit to the Screw Drive
One of the more overlooked aspects is not correctly matching the screw drive to the type of screwdriver bit that you are using. This not only includes matching the correct shape, but the size as well.
For example, a torx plus drive requires a screwdriver bit designed to drive it correctly. However, you will also need to consider the size of the screw bit so that it fits snugly into the screw drive. If it is too loose, it can damage the screw drive when turning.
There are different types of screw drives as well which include the following.
- Slotted: Simple, easy to use, but the bit tends to slip when driving the screw.
- Philips: The cross-shaped slot allows for a firmer grip which makes driving the screw go faster.
- Pozidriv: An improved version of the Philips drive.
- Square Drive: Also known as Robertson drive, these screws have square socket.
- Pentalobe: A 5-point star-shaped drive that is often found Apple’s electronic products.
- Torx: Similar to the pentalobe, but with 6-point contact. It has more areas of contact and can withstand higher torque without cam out (stripping).
- Hex: Hex drive or Allen screw have a socket with hexagonal drive slot.
Screw Head Shape
At first glance, the shape of the screw head may not seem all that important. But the shape does have one major function. Whether the screw head will either protrude or penetrate the material itself.
Another important factor of screw head shapes is how tight they will hold when in place. When assembling products or items, the right screw head can make all the difference in how secure the final item will be. Some of the different screw head shapes include the following.
- Button: Similar to countersunk screws, but often used with a washer for extra security.
- Countersunk: Most often used with plaster or wood as they sink to the same level as the material.
- Cylindrical: A flat underside creates better contact with the surface of the material.
- Hexagonal: Hex bolts have hexagonal shaped head which you can loosen or tighten with a 6-point or 12-point wrench and even with an adjustable wrench. Most screw heads of this type use an Allen key or hex screw driver bit.
- Round: The most common shape
- Square: Square shaped heads are easier to drive with one hand.
Length & Diameter
Next, you will need to choose the right length of the screw so that it penetrates the material to the desired depth.
Keep in mind that not all screws need to fully penetrate the material itself. So, you will need to select the right length that you want to use, which means knowing the depth of the material that is part of your project.
Selecting the right diameter is next as you want the screw to be large enough to be fully secured in the materials, but not so large that it either damages the material or does not leave enough room for other applications to take place.
Another overlooked aspect is whether the length of the thread goes all the way to the tip. Some screw shafts have either the area near the screw head or the area near the screw tip as flat. These are specialized screws for use in specific jobs.
Different Screw Types
Screws are designed with specific jobs in mind, and understanding the differences can help you choose the right one for your project. Here’s a brief overview of common types:
- Wood: Wood screws are normally made from stainless steel or zinc, have a slotted head, partial threads, and a relatively small diameter.
- Chipboard: Chipboard screws can also be used for wood. They are quite similar to wood screws except they are fully threaded and often use the Pozidriv or Torx screw drive.
- Concrete: Although concrete screws have several different variations, they are most noted for their large threads. They are normally fitted into pre-drilled holes.
- Drywall: Drywall screws are distinguished by their countersunk Philips head, long, thin shaft, and sharp point.
- Lag: This type of screw is noted for its hexagonal head, pointed tip, and partial thread. They are normally made from stainless steel or zinc.
The advantage of using lag screws is that once in place, they are quite resistant to being removed. The pointed tip allows them to sink quickly and securely into the material.
- Metal: Metal screws are distinguishable by their flat tips as they are driven through pre-tapped holes.
- PVC: Made from stainless steel and with a countersunk head, they are similar to other types of screws save for the use of the Torx screw drive. The thin thread allows them to be driven without a plug.
- Self-Drilling Screws: As the name suggests, this type of screw can be used to drive through plastic, soft metals, and even this sheet metal. They have a countersink head which is often hexagonal in shape. Although some may have a button-shaped head.
There are different screw drives with this type of screw. And they are often used in automotive or construction industries.
- Sheet Metal: Are designed to fashion together sheet metal and may have pointed or flat tips. They look quite similar to wood and chipboard screws but are quite different in application.
And that represents the basic parts, types, and materials of screws that are commonly used.
Choosing the right screw for your project can make the difference between a successful, durable result and a shaky, insecure one. By considering the material you’re working with, the screw drive and bit, the head shape, length, diameter, thread length, and the type of screw that’s best for your project, you can ensure a successful outcome.
Additionally, understanding the unique attributes and applications of different screw types is essential. From wood and chipboard screws to more specialized screws such as lag, concrete, and self-drilling screws, each has its unique features that make them ideal for specific applications.
Keep this guide handy as you plan and execute your projects, and don’t be afraid to try different screws until you find the one that’s perfect for your needs.