Screws have more holding power than nails, making them a crucial tool for many projects. They also come in a variety of types and sizes for different materials and loads, ensuring the right fit in any given hole. Choosing the wrong screw size can result in poor connections or even damage the material. Fortunately, understanding the basics of screw size and measurement will help ensure you choose the right one for any project.
Screw dimensions are determined by three essential measurements: diameter, length, and thread pitch. While measuring a screw with a basic ruler or tape measure is fairly straightforward, using calipers will provide more precision and accurate measurements. Accuracy is especially important when working with small screws, as the slightest error can cause a screw to break or fail.
Measuring screw threads requires a more complex approach, as the number of turns in a given distance will determine the size of a screw’s threads. When measuring screw threads, the smallest diameter is called the minor diameter and the largest diameter is the major diameter. The middle of these two dimensions is called the pitch diameter, and it is the width of a theoretical cylinder that lies halfway between the major and minor diameters.
Finally, the length of a screw measures the distance from the base of the head (assuming it’s flat) to the tip. While a screw’s length can be measured with a ruler or tape measure, calipers offer a more precise reading, particularly when it comes to wood screws. Screws typically list their gauge and length on their packaging, with the gauge coming first and then the length in inches or millimeters. If they also include a thread count, it will usually appear between the gauge and length numbers like 10 x 2″. pilot hole 5/16 lag screw