A set square or triangle (
American English
American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lan ...
) is an object used in engineering and
technical drawing, with the aim of providing a
straightedge
A straightedge or straight edge is a tool used for drawing straight lines, or checking their straightness. If it has equally spaced markings along its length, it is usually called a ruler.
Straightedges are used in the automotive service and ma ...
at a
right angle
In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the ad ...
or other particular planar angle to a
baseline.
The simplest form of set square is a triangular piece of transparent
plastic (or formerly of polished wood) with the centre removed. More commonly the set square bears the markings of a
ruler and a half circle
protractor. The outer edges are typically
bevel
A bevelled edge (UK) or beveled edge (US) is an edge of a structure that is not perpendicular to the faces of the piece. The words bevel and chamfer overlap in usage; in general usage they are often interchanged, while in technical usage they ...
led. These set squares come in two usual forms, both
right triangles: one with 90-45-45 degree angles, the other with 30-60-90 degree angles. Combining the two forms by placing the
hypotenuses together will also yield 15° and 75° angles. They are often purchased in packs with
protractors and
compasses.
Less commonly found is the adjustable set square. Here, the body of the object is cut in half and rejoined with a
hinge
A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation: all other ...
marked with angles. Adjustment to the marked angle will produce any desired angle up to a maximum of 180°.
In some European countries a common form of set square combines a 90-45-45 triangle, a ruler and a protractor into a single tool made of stiff or slightly flexible transparent plastic.
Being a mandatory tool used by pupils in
middle school and higher in German-speaking and neighbouring countries, this specific design is named "" (short form of "", meaning "geometry triangle") or similar.
It was originally developed in 1964 by the German-Austrian manufacturer (after several refirmations now ''Geotec Schul- und Bürowaren GmbH'').
Relatively uncommon in English-speaking countries, this is sometimes called a "protractor triangle", a term, however, also used for other similar designs. The original design has a hypotenuse length of 15.8 cm and features a 2×7 cm symmetry scale in
millimeter and
degree raster.
Variants in larger sizes, with fixed or detachable handles, with or without bevelled edges (facets), and with or without ink nodules or embossed labels exist as well. Some variants have extra markings at angles of 7° and 42° (138° and 173°) in addition to the normal 45° and 90° markings to ease
dimetric axonometry per ISO 5456-3,
others feature angle scales in
gons instead of degrees. Several other somewhat similar designs named "" ("TZ triangle") exist for (larger) technical drawings (TZ from German: ). The scale reaches from 10 to 10 cm, or even 11 to 11 cm.
Navigation protractor triangles
Similar to the , a number of other protractor triangle types exist for
navigation purposes. Various designs are named navigation (protractor) triangle, nautical navigational triangle, nautical set square, Portland (navigational) triangle or Portland protractor triangle, Kent-type triangle, Inoue-type A/B nautical triangle or plotting triangle, course triangle, yachtsmen triangle, and supporting triangle.
However, some widely used navigational protractors, such as the
Cras protractor, are not triangles.
See also
*
Technical drawing tools
References
See also
*
Speed square A Swanson Speed Square.
A speed square, also called a rafter square, rafter angle square, and triangle square, is a multi-purpose triangular carpenters' tool use for marking out. Its functions include many of those of a combination square, try squ ...
*
Technical drawing tool
{{Authority control
Technical drawing tools
Hand tools
Squares (tool)