Speed square

diamond shape cutout at the 3 1/2 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. Swanson and other manufacturers make this tool in aluminum, steel, HDPE, and other composite materials.

Anatomy

The tool is shaped in an isosceles triangle and is marked with the word "Pivot" at the right angle point, Degrees on its hypotenuse, 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 3 1/2 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 complimentary.
*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 Speed 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 Speed Square 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.
#The Speed Square is held against the 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 Speed Square

The square consists of three parallel 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 @ 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.

External links

* [http://zo-d.com/stuff/how-do-i/how-to-use-the-swanson-speed-square-as-a-framing-square.html How to Use a Swanson Speed Square as a Framers Square]
* [http://www.iskills.com/apps/learningobjects/ViewFlash.jsp?fn=lo_raftersq.swf&sd=ace The Rafter-Angle Square]
* [http://www.homeconstructionimprovement.com/2008/08/how-to-use-swanson-speed-squares.html How To Use A Swanson Speed Square]