Rulers, also known as rulers and scales, are tools for drawing line segments (especially straight lines) and measuring length. There are usually scales on the ruler to measure the length. Some rulers have holes with special shapes, such as letters or circles, which are convenient for users to draw. They are usually used to measure and calculate the length, and are generally divided into tape measure, vernier caliper, ruler and ruler.

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A ruler, also called a middle ruler, has a precise straight edge and is used for measuring length and drawing. Widely used in mathematics, measurement, engineering and other disciplines. Rulers are widely used in mathematics, measurement, engineering and other disciplines. A ruler with a precise ruler. Rulers are used to measure straightness and flatness by light gap method, and can also be used to check length and size together with measuring blocks.

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Different materials, such as iron, wood, plastic, etc. A ruler has a certain hardness, otherwise it is a soft ruler. The minimum scale is generally1mm. The scale unit is usually centimeters. Length, common is 1 meter ruler and15cm short ruler, but there is no practical limit, so the length ranges from one centimeter to four or five meters.

There are two kinds of scale lines: top (the scale is at the beginning) and non-top (there is a blank in front of the scale line, about 1 cm). The maximum error is usually less than 0.2 mm. The maximum error is 0. 1mm within 30cm, 0. 15mm from 30cm to 50cm, and 0.2 mm from 50cm to 1mm.. ..

Rulers are widely used in mathematics, measurement, engineering and other disciplines. A ruler with a precise ruler. The straightedge is used to measure straightness and flatness by the light gap method, and can also be used together with the measuring block to check that the length dimension of the light gap method is the height of the boss of the workpiece. Before measurement, the dose block consists of two groups of sizes.

One group is equal to the maximum limit dimension of the tolerance of the boss height dimension, and the other group is equal to the minimum limit dimension. If the former is used to test, the contact between the ruler edge and the boss surface is transparent; In the latter inspection, the contact between the edge of the ruler and the measuring surface of the gauge block is transparent, indicating that the height and size of the boss are qualified. Rulers are usually made of rolling bearing steel.