A Caliper is a tool to compare measurements accurately, in almost all work activities at some point it is necessary to compare and take a measurement, depending on the measurement, this will have to be more or less accurate, in a case where there is no the need for precision a measuring tape or even a ruler can solve the problem, but when this precision is needed a caliper is an excellent tool option.

In the activities of an electrician, for example, the caliper can be used to measure a screw, to find out the diameter of a drill, to measure the depth of a motor brush cavity (to choose the correct brush), among many other uses.

A pachymeter is capable of carrying out four types of measurement on a given piece, because of these four measurements it is also known as a four-dimensional caliper. The four measures are:

- External measurement;
- Internal measurement;
- Depth measurement;
- Bounce measurement.

To know how to use it correctly, it is necessary to understand the parts that make up a caliper.

The caliper basically consists of two parts:

- Fixed part has a millimeter scale and one in inches, used to compare measurements

- Moving part, also called a vernier, has another scale that is used to compare and obtain the measurement and its precision.

And we still have two other important parts on the caliper:

- The lock, so as not to lose the measurements taken.
- Finger rest, used to slide the sliding scale more easily.

Very important information on the caliper is its precision, this information is recorded at the end of the vernier scale. Generally, a caliper is accurate to within one-hundredth of a millimeter.

In this example, a Starrett caliper was used with an accuracy of 0.05mm, that is, 5 hundredths of millimeters, which gives two places of precision after the comma.

## How to measure:

- The first step is to know exactly which of the four types of measurements will be performed and then position the caliper on the piece using the correct part of the caliper

- After placing the piece in the correct part of the caliper, observe where the 0 (zero) of the moving part (nonius) is and with which a number of the fixed part it is coinciding, this will indicate the first measurement number.

- In this case, the 0 (zero) of the vernier is between 4mm and 5mm of the fixed millimeter scale, this indicates that the first measurement number is 4mm.
- Then we see which marking coincides on both scales, fixed and mobile and we observe the number of the moving scale that coincided, this will be the second number, representing the tenths of millimeters.

- In the example coincided with the number 1, this will be the tenths of the 0.1mm measurement.

For this first example, the final piece size would be 4.1mm.

## Accuracy of hundredths:

This represented caliper has an accuracy of 0.05mm, that is, 5 hundredths of millimeters.

When, in the measure, the coincidence of the markings occurs between two whole numbers of the sliding scale, we will have a third number that are the hundredths of the measure, in the case of this caliper always multiple of 5.

### Example of measurement with hundredths of a millimeter:

- In this example, we see in the first drawing that the 0 (zero) of the sliding scale is between 4mm and 5mm (then representing 4mm), and in the second drawing that the coincident alignment on the sliding scale occurred between the number 1 and 2 in the 0 mark. , 05 (representing 0.15)