Speed square
Encyclopedia
A speed square or rafter angle square is a triangular
-shaped measuring tool used to draw straight lines on lumber
to be cut, or to lay out angle
s for roofs, stairways, decks and other general construction
. The tool is marked with degree gradations for fast layout and cutting of lumber without performing complex trigonometry
calculations. It was invented in 1925 by Albert J. Swanson. He called it the "Speed Square," since it provides a short cut for measurements and calculations of angles.
Speed Square is a registered trademark of the Swanson Tool Co., Inc., which continues to sell it under that name, though the name itself has become a genericized trademark
for all rafter angle squares. Modern Swanson squares can be differentiated from other manufacturer's rafter angle squares by their SPEED trademark and their trademark
ed diamond shape cutout at the 3½ inch mark, which assists in making birdsmouth
cuts.
Generally, the tool comes in two sizes - the compact 7 inch version for portable use and the larger less portable 12 inch version for stationary work. They may be made of aluminum, steel
, HDPE, and other composite materials.
A version of the 7 inch square is made by Stanley tools
under their name "Pocket Square".
, Common and Hip/Val markings on its mid-section parallel
to the hypothenuse, a ruler on one of the equal sides, and a fence on the other equal side. Some may have divots for fitting a writing utensil to mark lumber with. Genuine Swanson Speed Squares will also have a diamond shape cutout on the ruler side at 3½ in.
from 1 in. to 30 in.
The tool is used to cut Common, Hip, Valley and Hip or Valley Jack rafters, layout stringer
in stair fabrication, mark angles, determine angles, and to square off boards. It serves as a convenient straightedge and guide for circular saws (professionals recommend that the square be clamped when cutting splayed angles for safety).
Although there are slight differences in preparation, the usage of this tool is the same for measuring Degrees, Common, and Hip/Val.
lines to its hypotenuse
with markings on them. There is a degree line with increments of 1°, There are a common, and a hip-valley lines in increments of a one pitch to a 30 pitch.
The intersection of the pivot point (located at the tip of the 90° angle on the square) and where the readings coincide on the edge of the board determines the pitch or angle. The 12 inch square can be used to lay out stairs.
This tool uses a 0 degree reference. This means when a board is squared off the tool reads 0°. The angle derived is actually a complementary angle. For example a 22.5° angle is actually 67.5°. The sum of the angles equals 90° (22.5° +67.5° = 90°). It is obvious from a visual check that where the instruments displays 22.5° is not 22.5°. Many of the new slide miters and miter boxes display both angles. Some of the new calculators have a 0° and a 90° references to do angular calculations. This can create much confusion if it is not clearly understood.
Triangle
A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....
-shaped measuring tool used to draw straight lines on lumber
Lumber
Lumber or timber is wood in any of its stages from felling through readiness for use as structural material for construction, or wood pulp for paper production....
to be cut, or to lay out angle
Angle
In geometry, an angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle.Angles are usually presumed to be in a Euclidean plane with the circle taken for standard with regard to direction. In fact, an angle is frequently viewed as a measure of an circular arc...
s for roofs, stairways, decks and other general construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
. The tool is marked with degree gradations for fast layout and cutting of lumber without performing complex trigonometry
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...
calculations. It was invented in 1925 by Albert J. Swanson. He called it the "Speed Square," since it provides a short cut for measurements and calculations of angles.
Speed Square is a registered trademark of the Swanson Tool Co., Inc., which continues to sell it under that name, though the name itself has become a genericized trademark
Genericized trademark
A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
for all rafter angle squares. Modern Swanson squares can be differentiated from other manufacturer's rafter angle squares by their SPEED trademark and their trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
ed diamond shape cutout at the 3½ inch mark, which assists in making birdsmouth
Birdsmouth joint
In light frame construction, a birdsmouth joint is a woodworking joint that is generally used to connect a roof rafter to the top plate of a supporting wall...
cuts.
Generally, the tool comes in two sizes - the compact 7 inch version for portable use and the larger less portable 12 inch version for stationary work. They may be made of aluminum, steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, HDPE, and other composite materials.
A version of the 7 inch square is made by Stanley tools
Stanley Works
Stanley Black & Decker , formerly known as The Stanley Works, is a manufacturer of tools and hardware and provider of security products and locks headquartered in New Britain, Connecticut...
under their name "Pocket Square".
Anatomy
The tool is shaped in an isosceles triangle and is marked with the word "Pivot" at the right angle point, Degrees on its hypotenuseHypotenuse
In geometry, a hypotenuse is the longest side of a right-angled triangle, the side opposite the right angle. The length of the hypotenuse of a right triangle can be found using the Pythagorean theorem, which states that the square of the length of the hypotenuse equals the sum of the squares of the...
, Common and Hip/Val markings on its mid-section parallel
Parallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...
to the hypothenuse, a ruler on one of the equal sides, and a fence on the other equal side. Some may have divots for fitting a writing utensil to mark lumber with. Genuine Swanson Speed Squares will also have a diamond shape cutout on the ruler side at 3½ in.
- Degree markings indicate the angle in geometric degrees from 0° to 90°. Depending on which side is marked, the angle may be actual or complementary.
- Common markings indicate the rise in inches over a 12 inch run for common rafters
from 1 in. to 30 in.
- Hip/Val markings indicate the rise in inches over a 12 inch run for Hip or Valley rafters from 1 in. to 30 in.
- The fence, amongst other non-mathematical uses, is used to hold the square true against the lumber when using as a saw guide.
Usage
Swanson Co. advertises that the Speed Square can be used as a, "Try Square, Miter Square, Protractor, Line Scriber, & Saw Guide". The original Swanson Speed Square is famous for its "Little Blue Book" that accompanies the tool. The pocket sized reference book describes uses and methods for maximizing the utility of the tool, but more importantly, includes charts listing rafter lengths for the width of the building (from 3 to 40 ft). Generic versions of the tool do not come with any instructions.The tool is used to cut Common, Hip, Valley and Hip or Valley Jack rafters, layout stringer
Stringer
Stringer may refer to:* Stringer , a type of freelance journalism* Stringer * Stringer , or longeron, a strip of wood or metal to which the skin of an aircraft is fastened...
in stair fabrication, mark angles, determine angles, and to square off boards. It serves as a convenient straightedge and guide for circular saws (professionals recommend that the square be clamped when cutting splayed angles for safety).
Although there are slight differences in preparation, the usage of this tool is the same for measuring Degrees, Common, and Hip/Val.
- The square is held against the lumber with its fence flush to the material's length with the ruler facing the ridge end of the lumber.
- The tool is slid laterally to adjusted the Pivot point to the desired top cut position.
- The tool is turned away from the lumber anchored at the Pivot point until the desired Degree marking is met on the same side of the lumber as the pivot point.
- A line is scribed on the side with the ruler markings.
Marking angles using the square
The square consists of three parallelParallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...
lines to its hypotenuse
Hypotenuse
In geometry, a hypotenuse is the longest side of a right-angled triangle, the side opposite the right angle. The length of the hypotenuse of a right triangle can be found using the Pythagorean theorem, which states that the square of the length of the hypotenuse equals the sum of the squares of the...
with markings on them. There is a degree line with increments of 1°, There are a common, and a hip-valley lines in increments of a one pitch to a 30 pitch.
The intersection of the pivot point (located at the tip of the 90° angle on the square) and where the readings coincide on the edge of the board determines the pitch or angle. The 12 inch square can be used to lay out stairs.
This tool uses a 0 degree reference. This means when a board is squared off the tool reads 0°. The angle derived is actually a complementary angle. For example a 22.5° angle is actually 67.5°. The sum of the angles equals 90° (22.5° +67.5° = 90°). It is obvious from a visual check that where the instruments displays 22.5° is not 22.5°. Many of the new slide miters and miter boxes display both angles. Some of the new calculators have a 0° and a 90° references to do angular calculations. This can create much confusion if it is not clearly understood.