Choosing the right screw size is an important part of any fastener assembly. Knowing how to measure screw diameter and thread pitch is also essential. These measurements can be made using a variety of tools but precise results can be achieved with a Vernier Caliper.
The first number on a screw size chart refers to the major diameter of the screw threads, measured along the crests (or peaks) of the threads, and is also known as the thread pitch. The second number is the unified thread standard designation, usually referring to coarse or fine, and sometimes to a specific coarse or fine thread series within that overall category.
When measuring a screw’s diameter, it is important to know whether the screw is countersunk or round-headed. For non-countersunk screws with a rounded head, you should begin your measurement where the oval top of the screw would rest on the material’s surface, and for countersunk screws, where the hole in the rounded head would be.
Screws are rated by their major diameter and thread pitch, which determine how far they can be driven into the material and how much force is required to resist tensile stress. Different screw sizes are used in different materials and applications, so selecting the correct one is crucial for the success of any project.
Studies have shown that larger diameter screws improve fixation of osteoporotic vertebrae, but only if the screw is placed at the correct depth. Inconsistent screw lengths can lead to problems in the long-term and may require the use of an extension. #6 screw diameter