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A compass, also commonly known as a pair of compasses, is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, it can also be used as a tool to mark out distances, in particular, on maps. Compasses can be used for mathematics, drafting, navigation and other purposes.




Prior to computerization, compasses and other tools for manual drafting were often packaged as a set with interchangeable parts. By the mid-twentieth century, circle templates supplemented the use of compasses.[citation needed] Today those 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.
Construction and parts
Compasses are usually made of metal or plastic, and consist of two "legs" connected by a hinge which can be adjusted to allow changing of the radius of the circle drawn. Typically one leg has a spike at its end for anchoring, and the other leg holds a drawing tool, such as a pencil, a short length of just pencil lead or sometimes a pen.
Handle
The handle, a small knurled rod above the hinge, is usually about half an inch long. Users can grip it between their pointer finger and thumb.
Legs
There are two types of leg in a pair of compasses: 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 through the hinge holds the two legs in position. The hinge can be adjusted, depending on desired stiffness; the tighter the hinge-screw, the more accurate the compass's performance. The better quality compass, made of plated metal, is able to be finely adjusted via a small, serrated wheel usually set between the legs (see the "using a compass" animation shown above) and it has a (dangerously powerful) spring encompassing the hinge. This sort of compass is often known as a "pair of Spring-Bow Compasses".
Needle point
The needle point is located on the steady leg, and serves as the center point of the circle that is about to be drawn.
Pencil lead
The pencil lead draws the circle on a particular paper or material. Alternatively, an ink nib or attachment with a technical pen may be used. The better quality compass, made of metal, has its piece of pencil lead specially sharpened to a "chisel edge" shape, rather than to a point.
Adjusting nut
This holds the pencil lead or pen in place.
Uses
Circles can be made by pushing 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 legs at the same angle. Some people who find this action difficult often hold the compasses still and move the paper round instead. The radius of the intended circle can be changed by adjusting the initial angle between the two legs.
Distances can be measured on a map using compasses with two spikes, also called a dividing compass (or just "dividers"). 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.
Compasses and straightedge
Compasses-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
A beam compass is an instrument, with a wooden or brass beam and sliding sockets, cursors or trammels, for drawing and dividing circles larger than those made by a regular pair of compasses.
Scribe-compasses is an instrument used by carpenters and other tradesmen. Some compasses can be used to draw 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. A wing nut on the hinge 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 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 with some accuracy.
A reduction compass or proportional dividers is used to reduce or enlarge patterns while conserving angles.
Ellipse drawing compasses are used to draw ellipse.
- Keuffel & Esser Arrow beam compass set for drafting.
- 18th-century ellipse-drawing compass (MHS Geneva)
- Simple reduction compass (MHS Geneva).
- Sliding-pivot reduction compass by Nairne on London, 18th century (MHS Geneva).
As a symbol
A pair of compasses 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 inch (15 cm) dividers made from forged steel.
- One type of sector.
- A compass on the former National Emblem of East Germany (former German Democratic Republic).
- The compass is a Masonic symbol that appears on jewellery such as this pendant.
See also
- Dividers
- Circle
- Geometrography
- Masonic Square and Compasses
- Technical drawing tools
References
- a current vendor's product
-
This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "Beam-Compasses". Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.
- Fine Woodworking, Build a Fireplace Mantel, Mario Rodriquez, pgs. 73, 75, The Taunton Press, No. 184, June 2006
- The Carpenter's Manifesto, Jeffrey Ehrlich & Marc Mannheimer, Holt, Rhinehart & Winston, pg. 64, 1977
- Fine Woodworking, Laying out dovetails, Chris Gochnour, pg. 31, The Taunton Press, No. 190, April 2007
External links
Compass (drafting) (category)
- Beam or trammel compass (variant form)
This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Compass drawing tool news newspapers books scholar JSTOR November 2023 Learn how and when to remove this message A compass also commonly known as a pair of compasses is a technical drawing instrument that can be used for inscribing circles or arcs As dividers it can also be used as a tool to mark out distances in particular on maps Compasses can be used for mathematics drafting navigation and other purposes A beam compass and a regular compassUsing a compassA compass with an extension accessory for larger circlesA bow compass capable of drawing the smallest possible circles Prior to computerization compasses and other tools for manual drafting were often packaged as a set with interchangeable parts By the mid twentieth century circle templates supplemented the use of compasses citation needed Today those 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 Construction and partsCompasses are usually made of metal or plastic and consist of two legs connected by a hinge which can be adjusted to allow changing of the radius of the circle drawn Typically one leg has a spike at its end for anchoring and the other leg holds a drawing tool such as a pencil a short length of just pencil lead or sometimes a pen Handle The handle a small knurled rod above the hinge is usually about half an inch long Users can grip it between their pointer finger and thumb Legs There are two types of leg in a pair of compasses 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 through the hinge holds the two legs in position The hinge can be adjusted depending on desired stiffness the tighter the hinge screw the more accurate the compass s performance The better quality compass made of plated metal is able to be finely adjusted via a small serrated wheel usually set between the legs see the using a compass animation shown above and it has a dangerously powerful spring encompassing the hinge This sort of compass is often known as a pair of Spring Bow Compasses Needle point The needle point is located on the steady leg and serves as the center point of the circle that is about to be drawn Pencil lead The pencil lead draws the circle on a particular paper or material Alternatively an ink nib or attachment with a technical pen may be used The better quality compass made of metal has its piece of pencil lead specially sharpened to a chisel edge shape rather than to a point Adjusting nut This holds the pencil lead or pen in place UsesCircles can be made by pushing 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 legs at the same angle Some people who find this action difficult often hold the compasses still and move the paper round instead The radius of the intended circle can be changed by adjusting the initial angle between the two legs Distances can be measured on a map using compasses with two spikes also called a dividing compass or just dividers 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 Compasses and straightedgeCompasses 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 VariantsA beam compass is an instrument with a wooden or brass beam and sliding sockets cursors or trammels for drawing and dividing circles larger than those made by a regular pair of compasses Scribe compasses is an instrument used by carpenters and other tradesmen Some compasses can be used to draw 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 A wing nut on the hinge 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 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 with some accuracy A reduction compass or proportional dividers is used to reduce or enlarge patterns while conserving angles Ellipse drawing compasses are used to draw ellipse Compass variantsKeuffel amp Esser Arrow beam compass set for drafting 18th century ellipse drawing compass MHS Geneva Simple reduction compass MHS Geneva Sliding pivot reduction compass by Nairne on London 18th century MHS Geneva As a symbolA computer drawn compass used to symbolize precise designing of applications A pair of compasses 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 inch 15 cm dividers made from forged steel One type of sector A compass on the former National Emblem of East Germany former German Democratic Republic The compass is a Masonic symbol that appears on jewellery such as this pendant See alsoMathematics portalDividers Circle Geometrography Masonic Square and Compasses Technical drawing toolsReferencesa current vendor s product This article incorporates text from a publication now in the public domain Chambers Ephraim ed 1728 Beam Compasses Cyclopaedia or an Universal Dictionary of Arts and Sciences 1st ed James and John Knapton et al Fine Woodworking Build a Fireplace Mantel Mario Rodriquez pgs 73 75 The Taunton Press No 184 June 2006 The Carpenter s Manifesto Jeffrey Ehrlich amp Marc Mannheimer Holt Rhinehart amp Winston pg 64 1977 Fine Woodworking Laying out dovetails Chris Gochnour pg 31 The Taunton Press No 190 April 2007External linksWikimedia Commons has media related to Compass drafting category Beam or trammel compass variant form