Wood Screw Sizes – How Are Screw Diameters Determined?

When it comes to wood screws, there’s a wide variety of sizes available. It’s important to understand how each screw size is determined before you make a purchase.

The diameter of a screw refers to the overall width of the threads. A screw with wider threads is more likely to penetrate into a thicker piece of lumber than one with narrower threads. Screws with narrower threads are usually used for smaller applications. The head of a screw is also important to consider. Screws with larger heads are better suited for heavy-duty projects, while smaller head screws have a more decorative appearance and can be used in craft work or light construction.

Most screw sizes are indicated by a number with an increasing number indicating a narrower screw. However, there are also a few other factors that come into play when determining the proper screw size for a particular application. Screws are often identified by their length and gauge, as well. A larger gauge number indicates a thicker shaft and is typically used for steel wood screws, while a smaller number is used for utility screws.

Screws are also designated by their tolerance class, which specifies how tightly the screw fits into holes and nuts. Tolerance classes range from class 1 to class 5, with higher numbers indicating tighter fits. Screws may also be specified as being left-handed, which is an indicator that they are threaded in reverse.

The surface of a screw must be free from burrs, sharp edges, or other defects and must be capable of a smooth finish prior to coating. Surface roughness is measured axially on the body and fillet surfaces, as well as circumferentially on the head bearing surface.

Screw length requirements vary depending on the construction details. In general, a screw should be long enough to penetrate the bottom board by 2/3 the thickness of that board. This will ensure that the screw is secure and can support the weight of the material being fastened.

The most commonly used wood screw size is the #8 screw. This screw is the best choice for most woodworking projects and can be found in many hardware stores. There are also a number of different types of wood screws, such as utility and deck screws, that have a variety of uses. #12 screw diameter