wood screw

Self-Tapping Sheet Metal Screw, Wood Screw or Lag Screw?

When you’re choosing your screws for a project, it’s important to know what you need for the job. That decision isn’t always straightforward, though — you might be surprised which options work with your applications. From stainless self-tapping sheet metal screws to wood screws to lag screws, you have a lot of options. You want to make sure you pick the best tool for the material you’re working with on each specific job. To help you choose, you’ll want to consider how you’ll be using the screws in the project and what they’ll need to do.

At All Points Fasteners, we’re here to help you find the best solutions for your work, so we want to help you source the perfect fastener. Read on for some tips on the differences between screws and how to choose the one that works best with your materials.

Self-Tapping Sheet Metal Screws

Sheet metal screws are fully threaded and do not have a smooth shank under the head.  Even though they are sheet metal screws, many also use them in wood so they incorrectly call them wood screws or lag screws, both of which have smooth shanks under the head.

Wood Screws

wood screw

Wood screws are specifically designed for non-structural, wood-to-wood fastening. This screw type features threads designed for gripping into wood grains.  They have coarse threads to accommodate wooden textures. What sets wood screws apart is the smooth shank near the head. This space ensures that the screw can pull two wood pieces tightly together.

Lag Screws





Lag screws work best with heavy-duty materials or components that must withstand large loads. They have coarse threads and a tapered point. This screw type also features a square or hex head, so they require a wrench or ratchet to install.

What’s the Difference Between the Screw Types?

Even pros are confused at times about which fastener they are using on a job. They often wonder, what’s the difference between a wood screw vs. a metal screw and which do I need. When you are putting screws into wood, then they have to be wood screws right? Well, possibly…….One good clue to spot the difference between a wood screw vs. sheet metal screw is to check underneath the head of the screws.

If the screw is fully threaded with a sharp point, you most likely have a sheet metal screw.

If the screw only is about 2/3 threaded with a smooth shank underneath the head, you are looking at a wood screw. Typically in the past, wood screws were not case-hardened like sheet metal screws and, unlike sheet metal screws, were plain steel and not plated.

But these days, there are many more options available. Some companies carry case-hardened wood screws and many are now zinc plated which gives them more protection from corrosion. The purpose of the smooth shank underneath the head was so that the two pieces of wood being fastened would draw together once the threads pass through the first piece of wood.

Wood screws offer several benefits like their ability to act as clamps. These screws create torque between pieces of wood to pull them together. With glue, this clamp can be permanent. These screws are generally inexpensive, and there are many styles of wood screws available to suit wood hardness levels and length requirements. Compared to nails, wood screws can withstand more stress.

Then there is the lag screw which is also used in wood. Frequently a customer will ask for a lag screw when, in fact, he is wanting a #14×3 self-tapping Hex Washer Head Sheet Metal Type A screw that is often used in wood.  A true lag screw will not have an attached washer (lip) and will only be about ⅔ threaded with a long smooth shank under the head. Lag screws are self-tapping and can withstand significant stress.

The biggest benefit of self-tapping screws is how easy they are to use. Without the need to create threads in your material or use a nut as you would with a machine screw, you can apply self-tapping screws in seconds. Since these screws form their own mating threads, they also create a durable hold with the material you apply them to.

How to Decide Whether You Need Self-Tapping Sheet Metal Screws, Wood Screws or Lag Screws

When you’re making the decision, how do you decide which option works best for your project?

A quick way to figure out which one you want is to ask:

1. Does it have a smooth shank underneath the head? and …

2. Does it have an attached washer on the hex head.

As you can tell from the pictures above, lag screws and sheet metal screws look quite different. If you pay attention to these two key features, you can probably figure out which option goes with which type of screw pretty quickly.

While these subtle differences can help you identify each type of screw, they can also help you determine the best applications based on their features.

Other considerations for choosing your screw type depend on the material you’re using and the load strength you need. If you need screws for wood, for example, any of the above options will work, but wood screws are specifically designed to work well with wooden textures, and they may be the best option.

Using lag screws for wood is the better option when you’re working on heavy-duty construction projects. Since wood lag screws are designed to withstand heavy loads, they’re trustworthy for building doorways, railroads, and other large wooden structures.

Self-tapping sheet metal screws are ideal for many materials, including wood and metal.

Work With All Points Fasteners to Get the Right Screws for Your Project

Do you need additional information to make sure you’re using the right tools and supplies for the job? At All Points Fasteners, we’re here to help contractors with HVAC, roofing, and gutter applications across industries. Partner with us for trusted services to help you move forward. Whether you need specialized screws or other supplies for your work, we have you covered with a broad inventory of products. Have questions or concerns? Our helpful, knowledgeable team offers superior customer support to handle all your requirements.

Reach out to us for online chat support addressing product selection and use assistance or any other needs you may have. When you work with us, you can be confident you’ll get trusted resources to help you know exactly what you need for your project. We’re committed to providing live-person assistance and expertise to help you handle your next job. To get more information about our products, feel free to get in touch with us and request a product quote today.

Head Screw Lady Since 1986! Specializing in breaking down the language barrier between suppliers and end users. During her 35 years working in the fastener industry, MaryLouise has worked directly with end users, contractor’s, OEM’S and DIY, as well working within the import industry, working with fastener manufacturers and distributors. This has given her the unique perspective of having the technical knowledge needed to perform in the fastener world but also be familiar with the needs of end users who don’t necessarily know the fastener jargon or applications to know exactly what they need for their jobs.