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The design was first proposed by the British Association in 1884 [1] [2] with a thread angle and depth based on the Swiss Thury thread, [3] it was adopted by the Association in 1903. The Thury thread was different in that it went both positive and negative all the way up to a size of −20 which was 75.2 mm diameter by 8.23 mm pitch ( p ).
Class 3 threads are medium fit, still quite common and used for closer tolerances on high quality work. Class 4 threads previously designated a close fit for even tighter tolerances, but this classification is now obsolete. Class 5 fit is an interference thread, requiring the use of a wrench for turning. These can be seen in applications like ...
Pipe Thread Form ANSI B1.20.3-1976 (R2013) Dryseal Pipe Threads (Inch) Pipe Thread Form ASME B1.20.7-1991 (R2013) Hose Coupling Screw Threads - Inch: Pipe Thread Form ASME B1.21M-1997 (R2013) Metric Screw Threads - MJ Profile: V Thread Form BS 84: Tables of BS Whitworth, BS Fine and BS Pipe Threads: V Thread Form (55°) 1 ⁄ 4 ″-20 BSW ISO ...
The screw itself should be drilled a minimum of 1" into the concrete to hold effectively and a maximum of 1-3/4" or the threads will wear and will lose holding power. Ideally 1-1/4" to 1-1/2" of screw thread in the concrete. [1] So for example, if a 1/2" board is being screwed onto the concrete, a 1-3/4" to 2" concrete screw should be used ...
For a taper thread, it is the diameter at the "gauge length" (plus/minus one thread pitch) from the small end of the thread. The taper is 1:16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.
Confusion can arise because each Whitworth hexagon was originally one size larger than that of the corresponding BSF fastener. This leads to instances where for example, a spanner marked 7 ⁄ 16 BSF is the same size as one marked 3 ⁄ 8 W. In both cases the spanner jaw width of 0.710 in, the width across the hexagon flat, is the same.
Sizes that may interchange, depending on the precision needed, include 2 mm (close to 5 ⁄ 64 inch (1.98 mm)), 4 mm (close to 5 ⁄ 32 inch (3.97 mm)) and 8 mm (close to 5 ⁄ 16 inch (7.94 mm)). In reality, a wrench with a width across the flats of exactly 15 mm would fit too tightly to use on a bolt with a width across the flats of 15 mm.
The standard for Nominal Pipe Size (often abbreviated NPS, which should not be confused with the abbreviation NPS for the straight thread form standard) is loosely related to the inside diameter of Schedule 40 series of sizes. Because of the pipe wall thickness of Schedule pipe, the actual diameter of the NPT threads is larger than the Nominal ...