Choosing the right screw can feel challenging when you don’t know what the different heads, shanks and points can do. By understanding these aspects, you will be able to find the best self-tapping screw for your project without having to ask for assistance.
The screw head you use will affect the stress distribution and finish of your project. Common head types include:
The shank is the threaded shaft of the screw, and different sizes offer various qualities. You’ll see shank sizes listed as a number without a unit of measure. The larger the number, the larger the shaft diameter. Hex Washer Head sizes often have standard shaft sizes to accommodate typical applications. These standards are:
While these are industry standards, there are exceptions. For example, zip screws for the gutter industry use a high profile 1/4″ hex head with #10 shanks. In the 1980s, #8 shanks were standard for gutter applications, but with the change in wood quality, #10 shanks respond better to knots today. Our hex head gutter screws also have a filet for extra strength.
Threads are the spiral shape around a screw’s shank. The threads per inch (TPI) affect how effectively a screw works through a material. Generally, a lower TPI is better for softwoods, and a higher TPI is better for metal and hardwoods.
Threads per inch are a clear example of why choosing the right screw is essential for your project. Any screw can snap if it experiences too much force. The threads are finer (more threads per inch) when you go into harder woods or metal so that the screw penetrates slower, otherwise, the screw will snap. Most users think that they received ‘bad’ screws when they actually just have the wrong screw for their application. The right TPI can ensure smoother fastening and fewer wasted screws.
A screw’s point affects how it interacts with metal during initial material entry. The most common types of screw points are:
While these are the two general point categories, there are other specialty points for specific applications. For example, type 17 screws have a fluted point for capturing wood chips and preventing splits.
The plating will affect how your screw interacts with its environment. Zinc plating is standard for most interior screw applications, and it can last up to two years. Hot-dipped and mechanical galvanized screws can last up to five years. These two types are the traditional plating styles, but other types include:
Now that you know how to choose the right screw for your application, you need to know how to find it based on the label. Self-tapping screws will have a label that reads “8-18×1 HWH SDS Z/P.” In order, the label means: