measuring tool

Instrument used to measure dimensions. In constructing an item, measurements are taken before cutting the material in order to mark accurately the positions for cutting. Measurements can be taken in one direction to measure length, two directions to measure area, or in three different directions to measure depth of cut. Measurements may be taken in a straight line (linear), at an angle, or along a curve (arc or circle).

To measure length a ruler or a pair of dividers is usually used. To measure angles a compass, try square (90°), mitre try square (45° or 135°), or sliding bevel is used. To measure curves or full circles a pair of compasses is used. Callipers can be used to measure the internal or external diameter of pipes and tubing. All these tools are accurate to within one millimetre. For more accurate measurements vernier callipers (accurate to within 0.1 mm) or micrometer screw gauges (accurate to within 0.01 mm) can be used. Coordinate measuring machines (CMM) are used in industry to measure and check the accuracy of parts. They can take simple measurements and are also able to work to within a few microns.