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The common V-thread standards (ISO 261 and Unified Thread Standard) include a coarse pitch and a fine pitch for each major diameter. For example, 1 ⁄ 2-13 belongs to the UNC series (Unified National Coarse) and 1 ⁄ 2-20 belongs to the UNF series (Unified National Fine). Similarly, M10 (10 mm nominal outer diameter) as per ISO 261 has a ...
This number pair is optionally followed by the letters UNC, UNF or UNEF (Unified) if the diameter-pitch combination is from the coarse, fine, or extra fine series, and may also be followed by a tolerance class. Example: #6-32 UNC 2B (major diameter: 0.1380 inch, pitch: 32 tpi)
The terms coarse and fine have (in this context) no relation to the manufacturing quality of the thread. In addition to coarse and fine threads, there is another division of extra fine, or superfine threads, with a very fine pitch thread. Superfine pitch metric threads are occasionally used in automotive components, such as suspension struts ...
United States Standard thread (USS thread), also known as Sellers Standard thread, [1] Franklin Institute thread [1] and American Standard thread, [2] is a standard for inch based threaded fasteners and washers. [3] The USS standard is no longer supported. It, together with the SAE fastener standard, was incorporated into the Unified Thread ...
Thus, if the thread pitch is p, the height of the fundamental triangle is H = p/(2tanΘ) = 0.96049106p. However, the top and bottom 1 ⁄ 6 of each of these triangles is cut off, so the actual depth of thread (the difference between major and minor diameters) is 2 ⁄ 3 of that value, or h = p/(3tanΘ) = 0.64032738p.
It specifically applies to fasteners that have an ISO metric screw thread as defined in ISO 68-1. The properties are defined for M1.6-39 with coarse threads and M8-39 with fine threads. The diameter and pitch combinations must adhere to ISO 261 and ISO 262 and the thread tolerances must adhere to ISO 965 parts 1, 2, and 4. [2]
The most commonly used pitch value for each diameter is the coarse pitch. For some diameters, one or two additional fine pitch variants are also specified, for special applications such as threads in thin-walled pipes. ISO metric screw threads are designated by the letter M followed by the major diameter of the thread in millimetres (e.g. M8).
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread.