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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 ).
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.
Example (inch, coarse): For size 7 ⁄ 16 (this is the diameter of the intended screw in fraction form)-14 (this is the number of threads per inch; 14 is considered coarse), 0.437 in × 0.85 = 0.371 in. Therefore, a size 7 ⁄ 16 screw (7 ⁄ 16 ≈ 0.437) with 14 threads per inch (coarse) needs a tap drill with a diameter of about 0.371 inches.
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 ...
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 ...
A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (the maximum thread diameter) and the pitch P, both expressed in millimetres and separated by a dash or sometimes the multiplication sign, × (e.g. M8-1.25 or M8×1.25).
Alternatively it is a short length of pipe with two female National pipe threads (NPT) (in North American terms, a coupler is a double female while a nipple is double male) or two male or female British standard pipe threads. If the two ends of a coupling are of different standards or joining methods, the coupling is called an adapter. Examples ...
375 ml (3 ⁄ 8 L) 500 ml (1 ⁄ 2 L) 750 ml (3 ⁄ 4 L) 1 L; 1.5 L; 2 L; 3 L; 5 L; In the United States, the alcohol industry switched to metric bottle sizes on October 1, 1976, abandoning the existing 38 sizes of bottles and instead adopting the following 6 sizes: [2] 50 mL (miniature) 200 mL (replaced the half-pint) (≈237 mL is a U.S. half ...