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Drill bit sizes are written as irreducible fractions. So, instead of 78/64 inch, or 1 14/64 inch, the size is noted as 1 7/32 inch. Below is a chart providing the decimal-fraction equivalents that are most relevant to fractional-inch drill bit sizes (that is, 0 to 1 by 64ths).
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.
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.
Subdivisions of an inch are typically written using dyadic fractions with odd number numerators; for example, two and three-eighths of an inch would be written as 2 + 3 / 8 ″ and not as 2.375″ nor as 2 + 6 / 16 ″. However, for engineering purposes fractions are commonly given to three or four places of decimals and have been ...
Description Mm to 1 inch fraction ruler.svg. English: a ruler from 0 to 1 inch (in.) in 1/32 inch divisions below the line and 1/2 millimetre (mm) divisions above the line to give a visual representation of the approximations. Principally designed to help visually determine if a metric or imperial drill bit will suffice. Date.
Sizes are often expressed as a fraction of an inch, with a one in the numerator, and a decimal number in the denominator. For example, 1/2.5 converts to 2/5 as a simple fraction, or 0.4 as a decimal number. This "inch" system gives a result approximately 1.5 times the length of the diagonal of the sensor.
A less precise definition is one pica equals 0.166 inches (4.2 mm), and one point 0.01383 inches (0.351 mm). [ 27 ] [ 33 ] It was also noticed that 83 picas is nearly equal to 35 cm, so the Type Founders Association also suggested using a 35 cm metal rod for measurements, but this was not accepted by every foundry.
The thread form is defined by flats at the tip and root of the thread form. This flat length is defined as the pitch divided by eight. The thread depth, which is from flat to flat is 0.6495 times the pitch. [4] For 1⁄4 -inch (6.4 mm) screws and larger, the pitch is defined as: where P is the pitch and D is the diameter of the rough stock.