Screw sizing can be confusing to the uninitiated. There are many different kinds of screws and many sizes to choose from. Some are used in wood, others are made of metal, and still others have specialized uses such as in masonry. It is important to understand the intricacies of screw sizing so that you can determine which ones are suitable for your project. In order to do so, you must be familiar with a few basic facts.
Screws are typically sized by gauge and length. The gauge refers to the diameter of the thread, while the length indicates how far into the material the screw goes. In the case of wood screws, this is usually measured from under the head of the screw. Some heads are plain while others are knurled. In addition, some have a raised head while others have a recessed one.
When determining which screw is appropriate for a specific job, the first thing to consider is its size, or gauge. Screws are available in a wide range of sizes from #0 through #15. The higher the number, the larger the screw. Screws that do not need to match up with a mating part are typically denominated using industry Numeric Sizes preceded by a number.
Once you know the screw’s diameter, you can determine its pitch. This is the distance from the beginning of one thread to the beginning of the next. There are a variety of methods for measuring pitch, but the most common is to use a screw pitch gage.
In the case of a #12 screw, the major diameter is 7/32 inch and the pitch is 32 threads per inch (TPI). This makes the screw suitable for light construction tasks such as attaching hinges to wood or to wood studs.
When selecting a screw for a concrete or brick application, it is a good idea to use masonry screws instead of wood ones. These are specially designed for use in these types of applications and have longer threading that is coarser than the standard wood screws.
The screw’s type is also a factor to consider. Some types are designed for heavy-duty use, such as the #10 wood screw which is 7/32 inch in diameter and available in lengths up to 6 inches. Other types are designed for lighter use, such as finish screws which have smaller heads than wood screws and are used for attaching trim and molding.
Other screw types are used for metal, ceramics, glass and drywall. There are even screws that have been designed for use in electrical applications. These are often referred to as self-tapping screws and have specially tapered ends that allow them to penetrate into the material without requiring a pilot hole. #12 screw diameter