Ruler: Difference between revisions
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==Types== |
==Types== |
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Rulers have long been made of wood in a wide range of sizes. [[Plastics]] have been used since they were invented; they can be moulded with length markings instead of being [[wikt:scribe|scribed]]. Metal is used for more durable rulers for use in the workshop; sometimes a metal edge is embedded into a wooden desk ruler to preserve the edge when used for straight-line cutting. 12 [[inches]] or 30 [[centimeter|cm]] in length is useful for a ruler to be kept on a desk to help in drawing. Shorter rulers are convenient for keeping in a pocket. Longer rulers, e.g., 18 inches (45 cm) are necessary in some cases. Rigid wooden or plastic [[yardstick]]s, 1 yard long and metre sticks, 1 metre long, are also used. |
Rulers have long been made of wood and measer dicks in a wide range of sizes. [[Plastics]] have been used since they were invented; they can be moulded with length markings instead of being [[wikt:scribe|scribed]]. Metal is used for more durable rulers for use in the workshop; sometimes a metal edge is embedded into a wooden desk ruler to preserve the edge when used for straight-line cutting. 12 [[inches]] or 30 [[centimeter|cm]] in length is useful for a ruler to be kept on a desk to help in drawing. Shorter rulers are convenient for keeping in a pocket. Longer rulers, e.g., 18 inches (45 cm) are necessary in some cases. Rigid wooden or plastic [[yardstick]]s, 1 yard long and metre sticks, 1 metre long, are also used. |
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Desk rulers are used for three main purposes: to measure, to aid in drawing straight lines and as a straight guide for cutting and scoring with a blade. Practical rulers have distance markings along their edges. |
Desk rulers are used for three main purposes: to measure, to aid in drawing straight lines and as a straight guide for cutting and scoring with a blade. Practical rulers have distance markings along their edges. |
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Measuring instruments similar in function to rulers are made portable by folding (carpenter's folding rule) or retracting into a coil (metal [[tape measure]]) when not in use. When extended for use they are straight, like a ruler. The illustrations on this page show a 2-[[meter]] carpenter's rule which folds down to a length of 24 cm to easily fit in a pocket, and a 5-meter-long tape which retracts into a small housing. |
Measuring instruments similar in function to rulers are made portable by folding (carpenter's folding rule) or retracting into a coil (metal [[tape measure]]) when not in use. When extended for use they are straight, like a ruler. The illustrations on this page show a 2-[[meter]] carpenter's rule which folds down to a length of 24 cm to easily fit in a pocket, and a 5-meter-long tape which retracts into a small housing. |
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is the tailor's fabric [[tape measure]], a length of tape calibrated in inches and centimetres. It is used to measure around a solid body, e.g., a person's [[waist]] measurement, as well as linear measurement, e.g., inside leg. It is rolled up when not in use, taking up little space. |
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A ''contraction rule'' is made having larger divisions than standard measures to allow for shrinkage of a metal casting. They may also be known as a 'shrinkage'' or ''shrink'' rule.<ref>http://www.answers.com/topic/contraction-rule</ref> |
A ''contraction rule'' is made having larger divisions than standard measures to allow for shrinkage of a metal casting. They may also be known as a 'shrinkage'' or ''shrink'' rule.<ref>http://www.answers.com/topic/contraction-rule</ref> |
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Revision as of 23:51, 28 September 2010
A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing and engineering/building to measure distances and/or to rule straight lines. Strictly speaking, the ruler is essentially a straightedge used to rule lines[citation needed], but typically the ruler also contains calibrated lines to measure distances.[1]
Types
Rulers have long been made of wood and measer dicks in a wide range of sizes. Plastics have been used since they were invented; they can be moulded with length markings instead of being scribed. Metal is used for more durable rulers for use in the workshop; sometimes a metal edge is embedded into a wooden desk ruler to preserve the edge when used for straight-line cutting. 12 inches or 30 cm in length is useful for a ruler to be kept on a desk to help in drawing. Shorter rulers are convenient for keeping in a pocket. Longer rulers, e.g., 18 inches (45 cm) are necessary in some cases. Rigid wooden or plastic yardsticks, 1 yard long and metre sticks, 1 metre long, are also used.
Desk rulers are used for three main purposes: to measure, to aid in drawing straight lines and as a straight guide for cutting and scoring with a blade. Practical rulers have distance markings along their edges.
A type of ruler used in the printing industry is called a line gauge. These may be made from a variety of materials, typically metal or clear plastic. Units of measurement on a basic line gauge usually include inches, agate, picas, and points. More detailed line gauges may contain sample widths of lines, samples of common type in several point sizes, etc.
Measuring instruments similar in function to rulers are made portable by folding (carpenter's folding rule) or retracting into a coil (metal tape measure) when not in use. When extended for use they are straight, like a ruler. The illustrations on this page show a 2-meter carpenter's rule which folds down to a length of 24 cm to easily fit in a pocket, and a 5-meter-long tape which retracts into a small housing.
is the tailor's fabric tape measure, a length of tape calibrated in inches and centimetres. It is used to measure around a solid body, e.g., a person's waist measurement, as well as linear measurement, e.g., inside leg. It is rolled up when not in use, taking up little space.
A contraction rule is made having larger divisions than standard measures to allow for shrinkage of a metal casting. They may also be known as a 'shrinkage or shrink rule.[2]
Ruler applications in geometry
In geometry, a ruler without any marks on it (a straightedge) may be used only for drawing straight lines between points, not measuring.
A ruler and compass construction refers to constructions using an unmarked ruler and a compass. It is possible to bisect an angle into two equal parts with ruler and compass. It can be proved, though, that it is impossible to divide an angle into three equal parts using only a compass and straightedge — the problem of angle trisection. However, should a single mark be allowed on the ruler, the problem becomes solvable.
History
Rulers made of Ivory were in use by the Indus Valley Civilization period prior to 1500 BC.[3] Excavations at Lothal (2400 BC) have yielded one such ruler calibrated to about 1⁄16 in (1.6 mm).[3] Ian Whitelaw holds that the Mohenjo-Daro ruler is divided into units corresponding to 1.32 in (33.5 mm) and these are marked out in decimal subdivisions with amazing accuracy, to within 0.005 in (0.13 mm). Ancient bricks found throughout the region have dimensions that correspond to these units.[4]
Anton Ullrich invented the folding ruler in 1851.
See also
- Dividing engine
- Geometry template
- Golomb ruler
- Measuring rod
- Rolling ruler
- Scale rulers: architect's scale and engineer's scale
References
Notes
- ^ Dictionary.com definition
- ^ http://www.answers.com/topic/contraction-rule
- ^ a b Whitelaw, p. 14.
- ^ Whitelaw, p. 15.
Bibliography
- Whitelaw, Ian (2007). A Measure of All Things: The Story of Man and Measurement. Macmillan. ISBN 0312370261.
External links
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