tool for measuring angles

Figure di goniometri

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Technical drawing tools

Published on

29 June 2023

The protractor is a tool for measuring angles.
In the simplest type it consists of a circle (or a semicircle) with the circumference graduated and with a pointer in the center. By centering the pointer on the origin of the angle, and making the zero of the gradation coincide on one side, the value of the angle can be detected by reading the position of the other side along the graduated circumference.
The goniometers for office and for technical drawing are made of transparent plastic, in order to facilitate the reading of the position of the sides through the instrument itself. These, although not very precise, are also cheap.
Workshop protractors are made of a more robust material, typically stainless steel, to prevent rust from making reading difficult or erasing the scale. Often the surface is matted to avoid glare when reading.

How can you determine an angle on a sheet of paper with the protractor?

1 – draw a line representing one side of the corner with the square.

2 – place the center of the protractor on the end of the line chosen as the vertex of the angle and the other part of the line passing through the zero point of the protractor

3 – on the graduated scale of the protractor a point is marked on the desired angle.

4 – join the point of the vertex with the point found on the staircase with the bracket.

The two lines will have the desired angle.

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