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The development of the 'Tessar' lens is discussed by Nasse, [11] and shows its transformation from an f /6.3 lens for plate cameras using the original three-group configuration through to an f /2.8 5.2 mm four-element optic with eight extremely aspheric surfaces, economically manufacturable because of its small size. Its performance is 'better ...
The Charrière is measured by the ''outer'' diameter, and is defined as 1 Fr = 1/3 mm, and thus 1 mm = 3 Fr; therefore the diameter of a round catheter in millimetres can be determined by dividing the French size by 3. [2] The French units roughly correspond to the outer circumference of the catheter (see table below).
The thread form is slightly modified to increase the minor diameter, and thus the strength of screws and taps. The major diameter still extends to within 1 / 8 H of the theoretical sharp V, but the total depth of the thread is reduced 4% from 5 / 8 H = 5 / 8 cos(30°) P ≈ 0.541P to 0.52P.
In addition, 10 mm (0.393 in), and letter X (0.397 in) will work well, although major minus pitch by itself does not tell you this; but the 90% ± 2 pp guideline supports it. For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use.
Engineering G size is 22 + 1 ⁄ 2 in (572 mm) high, but it is a roll format with a variable width up to 90 in (2.3 m) in increments of 8 + 1 ⁄ 2 in (216 mm). Engineering H through N sizes are also roll formats.
British Standard Whitworth. British Standard Whitworth ( BSW) is an imperial-unit -based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basis for many other standards, such as BSF, BSP, BSCon, and BSCopper .
So a 1 / 2 in (12.7 mm) diameter drill will be able to drill a hole 4 + 1 / 2 in (114.3 mm) deep, since it is 9 times the diameter in length. A 1 / 8 in (3.175 mm) diameter drill can drill a hole 1 + 5 / 8 in (41.275 mm) deep, since it is 13 times the diameter in flute length. [3]
The recent formula used by the Brannock device assumes a foot length of 2 barleycorns less than the length of the last; thus, men's size 1 is equivalent to a last's length of 8 + 1 ⁄ 3 in (21.17 cm) and foot's length of 7 + 2 ⁄ 3 in (19.47 cm), and children's size 1 is equivalent to 4 + 1 ⁄ 4 in (10.8 cm) last's length and 3 + 7 ⁄ 12 in ...