The major diameter of a screw or bolt is the widest portion of the shank and is used to identify the size of the fastener. It plays a key role in screw identification systems, and can be measured using a micrometer. Suppliers provide charts to help identify screw measurements, including major and minor diameter and pitch. Knowing the major diameter helps workers choose the right screw for a project. Two main systems for identifying screws are the Unified Thread Standard (UPS) and the International Organization for Standards (ISO).
Major diameter is a measurement used to identify the size of a screw or bolt. The major diameter of these fasteners represents the distance around the outside portion of the threads, which is the widest portion of the shank. This measurement should be taken around the male threads and cannot be taken using the female portion of the threads or the head of the fastener. Major diameter plays a key role in most common screw identification systems, including metric and non-metric systems.
By using different measurements on a particular screw, users can identify the type of screw and how it can be used. Suppliers and manufacturers provide charts that allow users to find different screw measurements using known figures or characteristics. These measurements may include the major diameter or the minor diameter, which represents the size of the female threads along the shank. These graphs may also include pitch, which represents the number of threads per inch or centimeter measured along the length of the shank. By combining two or more of these measurements, users can identify a loose screw.
The major diameter of a screw or bolt can be measured using a hand tool known as a micrometer. Depending on the region, users may require a metric or non-metric micrometer tool. To get an accurate measurement with this tool, it’s critical to measure only around the widest portion of the threads on a screw. In some cases, excessive wear may have reduced the size of the threads, resulting in inaccurate measurements. Burrs or voids along the edges of the threads can also affect the accuracy of the reading.
Using the major diameter and other measurements, workers can identify the type of screw used on a particular project. This is useful for matching existing screws to create a secure, cohesive connection. With so many shapes and sizes of screws available, knowing the major diameter and another size makes it much easier to choose the right screw in the shop or workshop.
While people around the world use many different systems to identify types of screws, two main systems serve as the most widely used methods of identifying screws. These include the Unified Thread Standard (UPS) and the International Organization for Standards (ISO). According to UPS identification standards, screws are identified by a number which can be used to identify the size and pitch of the screw. To find the major diameter of a UPS screw, multiply the ID number by 0.13, then add 0.60, which gives you the diameter in inches. According to ISO identification standards, the major diameter is indicated as the first number in a sequence of numbers used to identify each screw.
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