A Swanson Speed Square. A Speed Square, also generically called a rafter square, rafter angle square, and triangle square, is a multi-purpose

triangular A triangle is a polygon with three corners and three sides, one of the basic shapes in geometry. The corners, also called ''vertices'', are zero-dimensional points while the sides connecting them, also called ''edges'', are one-dimensional ...

carpenters' tool used for

marking out Marking out or layout means the process of transferring a design or pattern to a workpiece, as the first step in the manufacturing process. It is performed in many industries or hobbies although in the repetition industries the machine's initial set ...

. Its functions encompass many of those offered by combination squares, try squares, and framing squares. Carpenters use it to make basic measurements and mark lines on

dimensional lumber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...

, and as a saw guide for short 45 and 90 degree cuts. "Speed Square" is a registered trademark of the Swanson Tool Company.

History

Albert J. Swanson invented the "A" Speed Square in 1925 as a carpenter's layout tool. He later founded the Swanson Tool Company to mass produce his invention. Today, the Swanson Tool Company still manufactures and distributes the Speed Square and other carpentry tools from its headquarters in

Frankfort, Illinois Frankfort is a village in Will County and Cook County in the U.S. state of Illinois. It is a southern suburb of Chicago, and is approximately 28 miles (45 km) south of the city. As of the 2020 census, the population was 20,296. Frankfo ...

Design

The Speed Square is manufactured from a variety of materials such as

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

, and composites such as

HDPE High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or " polythene" when used for HDPE pipes. With a high strength-to-density ratio ...

. They are also made in several sizes such as , and 250 mm. Embedded degree gradations on the tool eliminate the need for

trigonometric Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The field ...

calculations and allow for lines to be more easily made. The Speed Square tool is an

isosceles In geometry, an isosceles triangle () is a triangle that has two sides of equal length and two angles of equal measure. Sometimes it is specified as having ''exactly'' two sides of equal length, and sometimes as having ''at least'' two sides ...

right triangle A right triangle or right-angled triangle, sometimes called an orthogonal triangle or rectangular triangle, is a triangle in which two sides are perpendicular, forming a right angle ( turn or 90 degrees). The side opposite to the right angle i ...

with a ruler on one equal side and a

fence A fence is a structure that encloses an area, typically outdoors, and is usually constructed from posts that are connected by boards, wire, rails or net (textile), netting. A fence differs from a wall in not having a solid foundation along its ...

on the other. It is marked with the word ''Pivot'' at the right angle point and displays ''Degrees'' on its

hypotenuse In geometry, a hypotenuse is the side of a right triangle opposite to the right angle. It is the longest side of any such triangle; the two other shorter sides of such a triangle are called '' catheti'' or ''legs''. Every rectangle can be divided ...

, ''Common'' and ''Hip/Val'' markings on its midsection. *''Degree'' indicates the angle in degrees from 0° to 90°. *''Common'' indicates the rise in inches over a 12 inch run for common rafters from 1 inch to 30 inch. *''Hip/Val'' indicates the rise in inches over a 17 inch run for hip or valley rafters from 1 inch to 30 inch. Some models have divots for fitting a writing utensil to mark lumber with. Speed squares made by the Swanson Tool Company also have a diamond shape cutout on the ruler side at 3½ inches.

Usage

Among its basic uses are marking common,

hip In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint on t ...

, valley and hip, or valley jack rafters, laying out stair stringers, determining and marking angles, and making square cuts on boards. Common lines made using a speed square include perpendicular cut marks and Angle
definition of an angle
for roofs, stairways, and decks. The tool uses a 0° reference. This means when a board is squared off the tool reads 0°. The angle derived is actually a

complementary angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight lines at a point. Formally, an angle is a figure lying in a plane formed by two rays, called the '' sides'' of the angle, sharing ...

, for example a 22.5° angle is actually 67.5°. The sum of the angles equals 90 degrees (22.5° +67.5°= 90°). It is also obvious from a visual check when using a

protractor A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry derives from two Greek words, γωνία (''gōnía'') 'angle' and μέτρον (''métron'') ' me ...

that where the instruments displays 22.5° is actually 67.5° on the protractor. Many newer slide miters and miter boxes display both angles. Some of the new calculators have a 0° and a 90° references. The only true angle is 45° on the triangular square. This can create confusion if the user does not understand this angular calibration when using trigonometric functions. The FIRST image below shows ⊾ P = 20° on the protractor and ⊾ T = 20° on the angle Square. The only similarity is that both of the angles are

acute angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight lines at a point. Formally, an angle is a figure lying in a plane formed by two rays, called the '' sides'' of the angle, sharing ...

and complimentary. When the image is enlarged the protractor is on the ⊾ 20° index and the body rests on the edged face of the 2X4. The square is pivoted on the (left side 2x4) and locked into the ⊾ 20° degree index at the red marked line. The SECOND image displays ⊾ X = 70° on the clear protractor that is graduated in 360°, ⊾ X = 20° on the Aluminum angle square. Both red lines ⊾ X are Parallel and thereby congruent. "Postulate 4.1 (P 64)" congruent angle * File:Aluminum Angle Square and Plastic Protractor 02.jpg, Differences of Angle Square and Protractor File:Clear Protractor 01.jpg, compare 20° on Protractor and Angle Square

References

External links

How to Use a Swanson Speed Square as a Framers SquareSPEED SQUARE MADE SIMPLE
(video)

News

Framing BasicsComplementary AngleDefinition of an angle

Books

Bibliography

* * {{DEFAULTSORT:Speed Square Woodworking measuring instruments Dimensional instruments American inventions Squares (tool)