SHIPPMENT : SHIPP worldwide via
registered airmail is $ 25 . Will be sent inside a protective rigid packaging
. Handling around 5-10 days after payment.
A rolling ruler is a ruler that contains a cylinder much like a rolling pin inside, thereby enabling it to "roll" along a sheet of paper or other surface where it is being used. A rolling ruler can draw straight, parallel lines, and also has other instruments included, enabling it to do the jobs of a protractor and compass.[1][2] A protractor is a measuring instrument, typically made of transparent plastic or glass, for measuring angles. Most protractors measure angles in degrees (°). Radian-scale protractors measure angles in radians. Most protractors are divided into 180 equal parts. They are used for a variety of mechanical and engineering-related applications, but perhaps the most common use is in geometry lessons in schools. Some protractors are simple half-discs. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle. Contents 1 Bevel protractor2 Gallery3 See also4 References5 External links Bevel protractor Technical drawing tools are the tools used for technical drawing, including, and not limited to: pens, rulers, compasses, protractors, and drawing utilities. Drawing tools may be used for measurement and layout of drawings, or to improve the consistency and speed of creation of standard drawing elements. The tools used for manual technical drawing have been displaced in use by the advent of the personal computer and its common utilization as the main tool in computer-aided drawing, draughting and design, CADD. Technical drawing tools are the tools used for technical drawing, including, and not limited to: pens, rulers, compasses, protractors, and drawing utilities. Drawing tools may be used for measurement and layout of drawings, or to improve the consistency and speed of creation of standard drawing elements. The tools used for manual technical drawing have been displaced in use by the advent of the personal computer and its common utilization as the main tool in computer-aided drawing, draughting and design, CADD. A bevel protractor is a graduated circular protractor with one pivoted arm; used for measuring or marking off angles. Sometimes Vernier scales are attached to give more precise readings. It has wide application in architectural and mechanical drawing, although its use is decreasing with the availability of modern drawing software or CAD. Universal bevel protractors are also used by toolmakers; as they measure angles by mechanical contact they are classed as mechanical protractors.[1][2] The bevel protractor is used to establish and test angles to very close tolerances. It reads to 5 minutes or 1/12°[clarification needed] and can measure any angle from 0° to 360°. The bevel protractor consists of a beam, a graduated dial and a blade which is connected to a swivel plate (with Vernier scale) by thumb nut and clamp. When the edges of the beam and blade are parallel, a small mark on the swivel plate coincides with the zero line on the graduated dial. To measure an angle between the beam and the blade of 90° or less, the reading may be obtained direct from the graduation number on the dial indicated by the mark on the swivel plate. To measure an angle of over 90°, subtract the number of degrees as indicated on the dial from 180°, as the dial is graduated from opposite zero marks to 90° each way. Since the spaces, both on the main scale and the Vernier scale, are numbered both to the right and to the left from zero, any angle can be measured. The readings can be taken either to the right or to the left, according to the direction in which the zero on the main scale is moved. The above picture illustrates a variety of uses of the bevel protractor. Reading the Vernier scale: The bevel protractor Vernier scale may have graduations of 5′ (minutes) or 1/12°. Each space on the Vernier scale is 5′ less than two spaces on the main scale[clarification needed]. Twenty four spaces on the Vernier scale equal in extreme length twenty three double degrees[clarification needed]. Thus the difference between the space occupied by 2° on a main scale and the space of the Vernier scale is equal to one twenty-fourth of 2°, or 5′. Read off directly from the main scale the number of whole degrees between 0 on this scale and the 0 of the Vernier scale. Then count, in the same direction, the number of spaces from the zero on the Vernier scale to a line that coincides with a line on the main scale; multiply this number by 5 and the product will be the number of minutes to be added to the whole number of degrees. For example: Zero on the vernier scale has moved 28 whole degrees to the right of the 0 on the main scale and the 3rd line on the vernier scale coincides with a line upon the main scale as indicated. Multiplying 3 by 5, the product, 15, is the number of minutes to be added to the whole number of degrees, thus indicating a setting of 28 degrees and 15 minutes. Gallery A half circle protractor marked in degrees (180°). A 360° protractor marked in degrees. Another 360° protractor marked in degrees. A 400 gon protractor marked in gradians. A "Cras Navigation Plotter" double-protractor, in foreground. A half circle protractor marked in degrees (180°). A set square with integrated protractor (180°). See also Compass (drawing tool) for drawing circles or arcsFrench curveGoniometerInclinometerBirkhoff's axiomsTechnical drawing tools References 1. · Hearst Magazines (December 1993). Popular Mechanics. Hearst Magazines. pp. 76–. ISSN 0032-4558. Retrieved 7 July 2011. 2. · Farago, Francis T; Curtis (1994). Handbook of Dimensional Measurement. Industrial Press Inc. p. 580. ISBN 0-8311-3053-9. External links Wikimedia Commons has media related to Protractors. Printable protractor for download PDF (38.8 KiB)More printable protractorsHow to measure angles with a protractor An interactive animationHow to draw angles with a protractor An interactive animationAngle definition pages with interactive applets that are also useful in a classroom setting. Math Open Reference[1] Picture of bevel protractor.[2] Different bevel protractors.Inspection Methods - Angular MeasurementKha's protractor A compass (or pair of compasses) is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, they can also be used as tools to measure distances, in particular on maps. Compasses can be used for mathematics, drafting, navigation, and other purposes. Compasses are usually made of metal or plastic, and consist of two parts connected by a hinge which can be adjusted to allow the changing of the radius of the circle drawn. Typically one part has a spike at its end, and the other part a pencil, or sometimes a pen. Prior to computerization, compasses and other tools for manual drafting were often packaged as a "bow set"[1] with interchangeable parts. Today these facilities are more often provided by computer-aided design programs, so the physical tools serve mainly a didactic purpose in teaching geometry, technical drawing, etc. Contents 1 Construction and parts 1.1 Handle1.2 Legs1.3 Hinge1.4 Needle point1.5 Pencil lead1.6 Adjusting nut2 Uses3 Compass and straightedge4 Variants5 As a symbol6 See also7 References8 External links Construction and parts Compasses are usually made of metal or plastic, and consist of two parts connected by a hinge which can be adjusted to allow the changing of the radius of the circle drawn. Typically one part has a spike at its end, and the other part a pencil, or sometimes a pen. Handle The handle is usually about half an inch long. Users can grip it between their pointer finger and thumb. Legs There are two types of legs in a compass: the straight or the steady leg and the adjustable one. Each has a separate purpose; the steady leg serves as the basis or support for the needle point, while the adjustable leg can be altered in order to draw different sizes of circles. Hinge The screw on your hinge holds the two legs in its position; the hinge can be adjusted depending on desired stiffness. The tighter the screw the better the compass’ performance. Needle point The needle point is located on the steady leg, and serves as the center point of circles that are drawn. Pencil lead The pencil lead draws the circle on a particular paper or material. Adjusting nut This holds the pencil lead or pen in place. Uses Circles can be made by fastening one leg of the compasses into the paper with the spike, putting the pencil on the paper, and moving the pencil around while keeping the hinge on the same angle. The radius of the circle can be adjusted by changing the angle of the hinge. Distances can be measured on a map using compasses with two spikes, also called a dividing compass. The hinge is set in such a way that the distance between the spikes on the map represents a certain distance in reality, and by measuring how many times the compasses fit between two points on the map the distance between those points can be calculated. To use a compass, place the points on a ruler and open it to the measurement of ½ of the measurement of the circle that you want to draw. For instance, if you desire to draw a 3’’ circle, open the compass to 1 ½ ’’. Next, place the point (needle) on the spot that you wish the center of your circle to be, and then rotate the section that has the pencil lead around the point, using the handle. Compass and straightedge Compass and straightedge constructions are used to illustrate principles of plane geometry. Although a real pair of compasses is used to draft visible illustrations, the ideal compass used in proofs is an abstract creator of perfect circles. The most rigorous definition of this abstract tool is the "collapsing compass"; having drawn a circle from a given point with a given radius, it disappears; it cannot simply be moved to another point and used to draw another circle of equal radius (unlike a real pair of compasses). Euclid showed in his second proposition (Book I of the Elements) that such a collapsing compass could be used to transfer a distance, proving that a collapsing compass could do anything a real compass can do. Variants Beam compass is an instrument with a wooden or brass beam and sliding sockets, or cursors, for drawing and dividing circles larger than those made by a regular pair of compasses.[2] Scribe-compass [3] is an instrument used by carpenters and other tradesmen. Some compasses can be used to scribe circles, bisect angles and in this case to trace a line. It is the compass in the most simple form. Both branches are crimped metal. One branch has a pencil sleeve while the other branch is crimped with a fine point protruding from the end. The wing nut serves two purposes, first it tightens the pencil and secondly it locks in the desired distance when the wing nut is turned clockwise. Loose leg wing dividers [4] are made of all forged steel. The pencil holder, thumb screws, brass pivot and branches are all well built. They are used for scribing circles and stepping off repetitive measurements [5] with some accuracy. Proportional compass, also known as a military compass or sector, was an instrument used for calculation from the end of the sixteenth century until the nineteenth century. It consists of two rulers of equal length joined by a hinge. Different types of scales are inscribed on the rulers that allow for mathematical calculation. As a symbol A computer drawn compass, used to symbolize precise designing of applications. A compass is often used as a symbol of precision and discernment. As such it finds a place in logos and symbols such as the Freemasons' Square and Compasses and in various computer icons. English poet, John Donne used the compass as a conceit in "A Valediction: Forbidding Mourning" (1611). Compass for tracing a line. Flat branch, pivot wing nut, pencil sleeve branch of the scribe-compass. 6” Dividers made from forged steel. One type of sector. A compass on the Coat of Arms of East Germany (German Democratic Republic). The compass is a Masonic symbol that appears on jewellery such as this pendant. See also Masonic Square and CompassesDividersCircleGeometrographyTechnical drawing tools A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing, engineering and building to measure distances or to rule straight lines. The ruler is a straightedge which may also contain calibrated lines to measure distances.[1] Contents 1 Types2 Ruler applications in geometry3 History4 Curved and flexible rulers5 Philosophy6 Sticking to the ruler's marks7 See also8 References9 Bibliography10 External links Types Gilded Bronze Ruler - 1 chi = 23.1 cm. Western Han (206 BCE - CE 8). Hanzhong City, China Bronze ruler. Han dynasty, 206 BCE to CE 220. Excavated in Zichang County, China A flexible ruler unstretched. A flexible ruler stretched. Rulers have long been made of different materials and in a wide range of sizes. Some are wooden. Plastics have also been used since they were invented; they can be molded 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.[2] Longer rulers, e.g., 18 inches (45 cm) are necessary in some cases. Rigid wooden or plastic yardsticks, 1 yard long and meter sticks, 1 meter long, are also used. Classically, long measuring rods were used for larger projects, now superseded by tape measure or laser rangefinders. 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 line gauge is a type of ruler used in the printing industry. 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. A flexible length measuring instrument which is not necessarily straight in use is the tailor's fabric tape measure, a length of tape calibrated in inches and centimeters. 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.[3] A ruler software program can be used to measure pixels on a computer screen or mobile phone. These programs are also known as screen rulers. Ruler applications in geometry Main article: Compass and straightedge In geometry, a ruler without any marks on it (a straightedge) may be used only for drawing straight lines between points. A straightedge is also used to help draw accurate graphs and tables. 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 two marks be allowed on the ruler, the problem becomes solvable. History A wooden carpenter's rule and other tools found on board the 16th century carrack Mary Rose In the history of measurement many distance units have been used which were based on human body parts such as the cubit, hand and foot and these units varied in length by era and location.[4] In the late 18th century the metric system came into use and has been adopted to varying degrees in almost all countries in the world. Rulers made of Ivory were in use by the Indus Valley Civilization period prior to 1500 BC.[5] Excavations at Lothal (2400 BC) have yielded one such ruler calibrated to about 1⁄16 inch (1.6 millimetres).[5] Ian Whitelaw holds that the Mohenjo-Daro ruler is divided into units corresponding to 1.32 inches (33.5 millimetres) and these are marked out in decimal subdivisions with amazing accuracy, to within 0.005 inches (0.13 millimetres). Ancient bricks found throughout the region have dimensions that correspond to these units.[6] Anton Ullrich invented the folding ruler in 1851. Curved and flexible rulers The equivalent of a ruler for drawing or reproducing a smooth curve, where it takes the form of a rigid template, is known as a French curve. A flexible device which can be bent to the desired shape is known as a flat spline, or (in its more modern incarnation) a flexible curve. Historically, a flexible lead rule used by masons that could be bent to the curves of a molding was known as a lesbian rule.[7] Philosophy Ludwig Wittgenstein famously used rulers as an example in his discussion of language games in the Philosophical Investigations. He pointed out that the standard meter bar in Paris was the criterion against which all other rulers were determined to be one meter long, but that there was no analytical way to demonstrate that the standard meter bar itself was one meter long. It could only be asserted as one meter as part of a language game. Sticking to the ruler's marks When using a ruler use the smallest mark as the first estimated digit. For example, if a ruler's smallest mark is cm, and 4.5 cm is read, it is 4.5 (±0.1) or range 4.4 to 4.6 cm. The overall length of a ruler may not be accurate within the degree of the smallest mark and the marks may be imperfectly spaced within each unit. With both of these errors in mind, reading between the marks (to 4.55) does not increase one's confidence in the overall reading and may make it worse. See also science portal Accuracy and precisionDividing engineGolomb rulerMeasuring rod ebay1332