Straightedge


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straightedge

[′strād‚ej]
(design engineering)
A strip of wood, plastic, or metal with one or more long edges made straight with a desired degree of accuracy.

Straightedge

 

in machine building, a rule for testing the flatness and parallelism of a surface. Straightedges measure the maximum distance between points on the surface’s profile and a contiguous straight line—the edge of the rule.

Two types of straightedges are distinguished: toolmakers’ straightedges (master straightedges) and straightedges with a broad working surface. The master straightedges may have two edges, three faces, or four faces. Other straightedges have a broad working surface with a right angular or bow shape or I-beam cross section. Master straightedges are used to test the flatness and parallelism of a surface by means of the gap between the surface and the edge of the straightedge applied to it. It is thus possible to detect gaps of 1–5 microns (μ). Straightedges with broad working surfaces determine flatness and parallelism by measuring linear deviations of the surface being inspected in comparison with the surface of the straightedge, which is held on supports. Checking for flatness may also be done by painting the surface to be inspected and moving the straightedge across it; the paint will then be scraped off the raised portions of the surface. Angled straightedges are used only with this method.

Master straightedges are made in various lengths from 80 to 500 mm. Straightedges with broad working surfaces have lengths of 200 to 4,000 mm, and angled straightedges have lengths of 630 to 1,000 mm, with angles of 45°, 55°, and 60°. The working surfaces of master straightedges deviate from linearity by 0.6 to 4 μ, depending on the length and the degree of accuracy. The variation of flatness in straightedges with broad working surfaces depart from flatness by 2.5 to 100 μ.

N. N. MARKOV

straightedge, rod

1. A rigid, straight piece of wood or metal used to strike off a concrete, mortared, or plastered surface; a screed, 2.
2. A long piece of seasoned, planed wood having straight, parallel edges; used in construction to lay out straight lines and to align framing.
References in periodicals archive ?
The present paper shall present the construction of tangents to a given circle without indication of the location of its center, using a straightedge only.
Gauss proved that an n-sided regular polygon can be constructed by compass and straightedge if and only if n is equal to a power of 2, and, possibly, multiplied by distinct Fermat primes.
The Ames guide also has straightedge sides, which allow it to be used in actual creation of lettering as well.
It states: "While defininitely not a body modification term, many people involved in body modification consider themselves to be straightedge. The most basic form of straight-edge is a drug free lifestyle...." (32) Some tattoos have the added advantage for their aficionados of requiring specialized knowledge.
Use the straightedge to help you cut along a straight line.
These indices include the area of the rut below a straight line connecting the end points of the transverse profile, the total area below the straight lines connecting the maximum surface elevations, the maximum depth for each wheelpath between a 1.8-m straightedge placed across the wheelpath and the surface of the pavement, and the width of the rut based on a 1.8-m straightedge.
"It is wonderfully satisfying to make these pictures by hand, patiently, with pencil and paper, compass and straightedge," Goodman-Strauss adds.
In 1796, however, a young German mathematician, Carl Friedrich Gauss (1777-1855), worked out a method for constructing a heptadecagon (a polygon built up of seventeen sides of equal lengths and sometimes called a seventeengon in consequence), using a compass and straightedge only.
Straightedge (or strikeoff board); To remove excess concrete and bring the surface to grade (the desired level) after the concrete has been placed in the forms.
The Russian Constructivist Aleksandr Rodchenko, for example, programmatically empoyed geometric forms generated by such instruments as compass and straightedge specifically to obliterate personality.
"Fugazi was straightedge -- they probably didn't drink," he says.