Choosing a Screw

When choosing a screw, it’s important to consider the gauge and threads per inch (TPI). Some screws have both a gauge number and a TPI on their packaging. A screw that is labeled 6-32 x 1 1/2″ means that it is a size 6 wood screw with 32 TPI.

Wood screws gain strength from friction between the screw threads and the wood fibers that grip them. In order to increase this friction and prevent the screw from splitting, it’s a good idea to drill a pilot hole before driving a wood screw. This is particularly true with hardwoods like oak or walnut, but also in softwoods like pine or cedar.

Screw length is another consideration when choosing a screw. The longer the screw, the more it can be used to support heavy loads. However, too long of a screw can cause the head to break off.

For most construction jobs, a 1 1/4-inch or 1 5/8-inch drywall screw is suitable for use. These screws are inexpensive and easy to find in stores. For some specialized jobs, it may be necessary to use a thicker drywall screw, such as one used for increased soundproofing or that meets certain fire codes in commercial buildings.

The first number on a screw is the gauge, or diameter. Screws are typically labeled in sizes ranging from #0 to #14. The gauge number is then followed by a fraction of an inch and a decimal equivalent, such as.013″. Engineering Toolbox provides a handy chart that converts imperial screw sizes to decimal size, and vice versa.

In addition to the gauge and TPI, there are often other measurements on a screw’s packaging. You may see a tolerance class, the symbol LH if the screw is left-handed, and the screw length on the package.

The tolerance class is the number that indicates how tightly the screw fits into its intended hole or nut. Screws in a class 1 fit more loosely than those in a class 5. Screws in a class 2 fit tighter, while those in a class 3 fit the tightest. The tolerance class is indicated right after the screw’s gauge and TPI numbers on the packaging. Some manufacturers put the metric system measurements, in millimeters, on their packaging as well. This allows customers to easily compare the sizes of screws between different brands. This is a great way to avoid accidentally ordering the wrong size screws. In fact, many manufacturers will put both the imperial and metric system measurements on their packaging to ensure that contractors can work with either system. This is very useful when working on construction projects in multiple countries. In some cases, the metric system is even required by law in certain jurisdictions. If this is the case, it’s a good idea to have a metric screw size conversion table on hand. This will help you quickly match the metric screw size to your imperial screw gauge. This will save you time, effort and money. 1/4 screw diameter