Straightedge

Short description: Tool used for drawing straight lines, or checking their straightness or flatness

File:Straight edge MET 187601.jpgAn ornate 18th century iron straightedge

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]

## Contents

* 1 Compass-and-straightedge construction
* 2 See also
* 3 References
* 4 External links

## Compass-and-straightedge construction

An idealized straightedge is used in compass-and-straightedge constructions in plane geometry.

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 compass so as to transfer the length of one segment to another.

It is possible to do all compass and straightedge constructions without the straightedge. That is, it is possible, using only a compass, to find the intersection of two lines given two points on each, and to find the tangent points to circles. It is not, however, possible to do all constructions using only a straightedge. It is possible to do them with straightedge alone given a circle and its center.

## See also

* Chalk line
* Geometrography

## References

1. ↑ "What is a straight edge tool?". https://www.maunindustries.com/blog/what-is-a-straight-edge-tool/.
2. ↑ Moore, Wayne R. (1970). Foundations of Mechanical Accuracy (1st, 3rd printing ed.). The Moore Special Tool Company. https://archive.org/details/FoundationsOfMechanicalAccuracy/page/n3/mode/2up.

## External links

* Making Accurate Straight-Edges from Scratch

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Metalworking

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Tools

Cutting machines|

* Bandsaw
* Cold saw
* Laser
* Miter saw
* Plasma
* Water jet cutter

Cutting tools|

* Broach
* Burr
* Chisel
* Counterbore
* Countersink
* End mill
* File
* Hand scraper
* Milling cutter
* Nibbler
* Reamer
* Shears
* Tipped tool
* Tool bit

Forming tools|

* Brake
* Die
* English wheel
* Hydraulic press
* Machine press
* Punch press
* Screw press
* Stamping press

Hand tools|

* Clamp
* Combination square
* Drift pin
* Hacksaw
* Hammer
* Hand scraper
* Machinist square
* Needlegun scaler
* Piercing saw
* Pliers
* Punch
* Scriber
* Tap and die
* Tongs
* Vise
* Workbench
* Wrench

Machine tooling|

* Angle plate
* Chuck
* Collet
* Fixture
* Indexing head
* Jig
* Lathe center
* Machine taper
* Magnetic base
* Mandrel
* Rotary table
* Wiggler

Measuring instruments|

* Bore gauge
* Caliper
* Center gauge
* Dial indicator
* Engineer's blue
* Engineer's spirit level
* Feeler gauge
* Gauge
* Gauge block
* Go/no go gauge
* Height gauge
* Machinist square
* Marking blue
* Marking gauge
* Marking out
* Micrometer
* Optical comparator
* Radius gauge
* Ruler
* Sine bar
* Straightedge
* Surface plate
* Tape measure
* Thread pitch gauge
* Vernier scale

Smithing tools|

* Anvil
* Forge
* Fuller
* Hardy tools
* Pritchel
* Steam hammer
* Swage block
* Trip hammer

* Casting
* Fabrication
* Forming
* Jewellery
* Machining
* Metallurgy
* Smithing
* Tools and terminology
* Welding

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Measuring and alignment tools

* Architect's scale
* Beam compass
* Calipers
* Chalk box
* Combination square
* Compass
* Coordinate-measuring machine
* Diagonal scale
* Drafting machine
* Engineer's scale
* Flat spline
* French curve
* Gunter's chain
* Jig
* Laser level
* Laser line level
* Laser measuring tool
* Lesbian rule
* Measuring rod
* Meterstick
* Micrometer
* Plumb-bob
* Protractor
* Radius gauge
* Ruler
* Set square
* Skirret
* Sliding T bevel
* Speed square
* Spirit level
* Steel square
* Stencil
* Straightedge
* T-square
* Tape measure
* Theodolite
* Thread pitch gauge
* Try square
* Vernier scale
* Vise
* Weighing scale
* Winding sticks

Types of tools
Cleaning
Cutting and abrasive
Forestry
Garden
Hand
Kitchen
Machine and metalworking
Masonry
Measuring and alignment
Mining
Power
Textile
Woodworking

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