Straightedge
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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 machining industry to check the flatness of machined mating surfaces. They are also used in the decorating industry for cutting and hanging wallpaper.[1]
True straightness can in some cases be checked by using a laser line level as an optical straightedge: it can illuminate an accurately straight line on a flat surface such as the edge of a plank or shelf.
A pair of straightedges called winding sticks are used in woodworking to make warping easier to perceive in pieces of wood.
Three straight edges can be used to test and calibrate themselves to a certain extent, however this procedure does not control twist. For accurate calibration of a straight edge, a surface plate must be used.[2]
Compass-and-straightedge construction
An idealized straightedge is used in
It may be used:
- Given two points, to draw the line connecting them
- Given a point and a circle, to draw either tangent
- Given two circles, to draw any of their common tangents
- Or any of the other numerous geometric constructions
The idealized straightedge is:
- Infinitely long
- Infinitesimally thin (i.e. point width)
- Always assumed to be without graduations or marks, or the ability to mark
- Able to be aligned to two points with infinite precision to draw a line through them
It may not be marked or used together with the
It is possible to
See also
References
- ^ "What is a straight edge tool?". Maun Industries. Retrieved April 24, 2023.
- ^ Moore, Wayne R. (1970). Foundations of Mechanical Accuracy (1st, 3rd printing ed.). The Moore Special Tool Company.