Steel ruler

The steel ruler is the simplest length measuring tool. It has four kinds of length: 150,300,500 and 1000mm. Below is a commonly used 150mm steel ruler.

The steel ruler is used to measure the length and size of the parts, but its measurement result is not very accurate. This is because the line spacing of the steel ruler is 1mm, and the width of the line itself is 0.1 ~ 0.2mm, so the reading error is relatively large when measuring, can only read the number of millimeters, that is, its minimum reading value is 1mm, smaller than 1mm, can only be estimated.

If the steel ruler is used to directly measure the diameter of the parts (axle diameter or aperture), the measurement accuracy is worse. The reason is: in addition to the large reading error of the steel ruler itself, the steel ruler can not be placed in the correct position of the diameter of the part. Therefore, the measurement of the diameter of the parts can also be carried out by using the steel ruler and the inner and outer calipers.

two

The internal and external calipers

Below are two common internal and external calipers. The inner and outer calipers are the simplest measure for comparison. The outer caliper is used to measure the outer diameter and plane, and the inner caliper is used to measure the inner diameter and groove. They do not directly read the measurement results, but the measured length size (diameter also belongs to the length size) is read on the steel ruler, or on the steel ruler to remove the required size, and then to check the diameter of the part is consistent.

1. The shape of the caliper opening should be checked first. The shape of the caliper has a great influence on the measurement accuracy, so attention should be paid to trimming the shape of the caliper often

Good versus bad jaws shape.

When adjusting the opening of the caliper, the two sides of the caliper foot should be gently tapped. Use both hands to adjust the caliper to the opening close to the size of the workpiece, then tap the outside of the caliper to reduce the opening, tap the inside of the caliper to increase the opening. This is shown in Figure 1 below. However, you cannot directly tap the jaws, as shown in Figure 2 below. This will cause measurement errors due to the damage of the caliper's jaws on the measuring surface. Do not hit the caliper on the guide rail of the machine tool. This is shown in Figure 3 below.

2, the use of the outer caliper outside the caliper on the steel ruler to remove the size, as shown below, a clamp foot measurement surface on the end face of the steel ruler, the other clamp foot measurement face of the required size of the middle of the line, and the two measuring surface should be parallel to the steel ruler, the person's line of sight should be perpendicular to the steel ruler.

With the third take good measure outside calipers on the steel ruler to measure the outside diameter, to make the two measuring the wire into the axis of the vertical components, rely on outside calipers weight slip when cylindrical parts we should hand feeling is outside calipers with cylindrical parts is point contact, outside calipers at this time the distance between the two measuring surface, is the outside diameter measured parts. Therefore, using the outer caliper to measure the outer diameter is to compare the tightness of the outer caliper and the outer circle of the parts. As shown below, the caliper's weight can just slide down as appropriate. Such as when the caliper slip through the outer circle, our hands do not touch the feeling, that the outer caliper than parts diameter size, such as the weight of the outer caliper can not slide through the outer circle parts, that the outer caliper than parts diameter size is small. Must not put the caliper on the workpiece askew measurement, so there is error. As shown in the figure below. Because the caliper is elastic, it is wrong to press the outer caliper across the outer circle, let alone clamp the caliper horizontally, as shown below. For the large-sized outer caliper, the measuring pressure of sliding through the outer circle of the part by its own weight is too large. At this time, the caliper should be held for measurement, as shown below.

3, the use of the inner caliper caliper measurement of the inner diameter, should make the two pliers foot measurement surface of the line just perpendicular intersecting the axis of the inner hole, that is, the two measuring surface of the pliers foot should be the two ends of the diameter of the inner hole. Therefore, the measuring surface of the following clamp foot should be stopped on the hole wall as a fulcrum.

The pliers foot from the hole opening slightly to the inside of some gradually outward testing, and swing along the circumference of the hole wall, when the distance along the circumference of the hole wall can swing for the minimum, it means that the two measuring surface of the inner caliper foot has been at the two ends of the diameter of the inner hole. Then move the caliper slowly from outside to inside to check the roundness tolerance of the hole.

Measure the inner diameter with the inner caliper that has been measured on the steel ruler or on the outer caliper.

It is to compare the tightness of the inner caliper in the holes of the parts. If the caliper in the hole there is a larger free swing, it indicates that the caliper size is smaller than the aperture; If the inner caliper can not be put into, or put into the hole after the tight can not swing freely, it means that the size of the inner caliper is larger than the aperture, if the inner caliper is put into the hole, according to the above measurement method can have a free swing distance of 1 ~ 2mm, then the aperture and the size of the inner caliper are exactly equal. Do not hold the caliper with your hand when measuring.

In this way, the feel is gone, it is difficult to compare the tightness of the inner caliper in the part hole, and the caliper deformation and measurement error.

4 calipers scope of caliper is a kind of simple measuring tool, because it has simple structure, easy fabrication, low cost, maintenance, and convenient use, etc, are widely used in the request is not high size measurement and inspection of parts, especially for malleable cast a blank dimensions measurement and test, caliper is the most suitable measuring tool. Calipers are simple measuring tools, as long as

If we master it well, we can also obtain high measurement accuracy. For example, comparing two with external calipers

When the diameter of the root shaft is large, the axle diameter difference is only 0.01mm, experienced master

You can tell the difference. If the inner caliper and the outside diameter percentage ruler are used to measure the inner hole size, the experienced master is completely sure to measure the inner hole with this method of high accuracy. This method of inner diameter measurement, known as the "inner clamp percentage gauge", uses inner calipers to read the exact dimensions on the outside diameter percentage gauge.

To measure the inner diameter of the parts; Or the card in the hole to adjust the tightness of the contact with the hole, and then read out the specific size on the outside diameter dial ruler. This measurement method is not only a good way to measure the inner diameter when there is no precise inner diameter measuring tool, but also for the inner diameter of a part, as shown in Figure 1-9, it is difficult to use the precise inner diameter measuring tool because there is a shaft in the hole, so the problem can be solved by using the inner caliper with outside diameter percentage ruler.