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ASpeed Square, also generically called arafter square,rafter angle square, andtriangle square, is a multi-purposetriangular carpenters' tool used formarking out. Its functions encompass many of those offered bycombination squares,try squares, andframing squares. Carpenters use it to make basic measurements and mark lines ondimensional lumber, and as a saw guide for short 45 and 90 degree cuts.
"Speed Square" is a registered trademark of the Swanson Tool Company.[1][2]
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.[3] Today, the Swanson Tool Company still manufactures and distributes the Speed Square and other carpentry tools from its headquarters inFrankfort, Illinois.
The Speed Square is manufactured from a variety of materials such asaluminum,steel, and composites such asHDPE. They are also made in several sizes such as 4, 6, 7, 8 and 12 in (100, 150, 180, 200 and 300 mm), and 250 mm.
Embedded degree gradations on the tool eliminate the need fortrigonometric calculations and allow for lines to be more easily made.
The Speed Square tool is anisoscelesright triangle with a ruler on one equal side and afence on the other. It is marked with the wordPivot at the right angle point and displaysDegrees on itshypotenuse,Common andHip/Val markings on its midsection.
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.
Among its basic uses are marking common,hip,valley and hip, orvalley jack rafters, laying out stairstringers, determining and marking angles, and making square cuts on boards.
Common lines made using a speed square include perpendicular cut marks and Anglesdefinition 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 acomplementary angle, 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 aprotractor that where the instruments displays 22.5° is actually 67.5° on the protractor. Many newer slidemiters andmiter 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 areacute angle 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 *ISBN 978-0-7641-3918-5
Mark: SPEED SQUARE [...] Goods and Services [...] For: Hand tools, namely, squares [...] Owner name: Swanson Tool Company, Inc.
Mark: SPEED [...] Goods and Services [...] For: HAND TOOLS, NAMELY; SQUARES [...] Owner name: SWANSON TOOL CO., INC.