King’s foot

The caliber or vernier caliper is a measuring tool that is used to obtain very precise measurements, both from its internal and external sides. Usually, it is used for mechanical tasks to know the exact size of some parts such as screws, shafts or gears. Let’s see what a gauge is and what it can be used for.

Mechanics and craftsmen, who have to carry out precision work, will know well what a caliber or vernier caliper is. These tools allow very precise measurements to be obtained , since they have several millimeter rulers on the inside and also on the outside. 

In this sense, the vernier caliper, also called a vernier caliper, has two sets of tweezers, one on the inside and the other on the outside. Each one has a different use, for example, those on the back are used to measure interiors, while the front ones, somewhat larger, are used to measure external diameters. On the other hand, among the parts of the vernier caliper, a depth probe stands out, with which very precise measurements of blind holes, cavities or slots can be obtained.

It will be better to go in parts, let’s start at the beginning.

What is a vernier caliper?

The vernier caliper, vernier or caliper, is a very precise measuring tool, which has a pattern to compare with the object that needs to be measured. Usually, it is used to obtain the measurements of the diameters, both external and internal, of the parts, with greater precision than that of a common rule.

How accurate is a gauge?

The caliber or vernier caliper has a precision of one tenth of a millimeter , that is, it can divide a millimeter into ten parts. In this sense, it is almost 100 times more precise than a common tape measure. On the other hand, the digital vernier caliper can reach a precision of one twentieth of a millimeter, that is, it can divide a millimeter into 20 parts.

Where does the name of vernier caliper come from?

Before the advent of the metric system, measurements were taken in feet, hands, or cubits. This system had a problem and that is, how long is a foot? Well, as you can imagine, feet were not the same in England as in Spain, just as the feet of two different people are not the same. It was for this reason that the measure of the foot of the king of each country was used as a reference , that is: a royal foot.

On the other hand, if you need to go from foot to meter and you are wondering how much a foot actually is; the answer is that one foot would be about 0.3048 meters.

What is a gauge for?

As we have already mentioned, its most basic use is to measure diameters and depth , usually in mechanical parts and other types of objects that require great precision.

In this sense, it is important that the objects that are measured are rigid, since the measurements are taken with its two sets of pliers. If the object is soft or pliable, the measurements will not be accurate, as the object deforms . For this reason, some of the most common uses of a vernier caliper are to measure the diameter of a threaded bolt, find the inside diameter of a nut, or measure the depth of a cylinder for engines.

Although a ruler could be used to obtain the diameter or depth of these pieces, the gauge is a tool that offers much higher precision. This is very important, since an error of two tenths of a millimeter in these parts could cause serious problems during assembly or even serious accidents.

In short, it is a highly appreciated tool for machining work, both for the lathe and for the milling machine, as well as for car mechanics.

What are the parts of the vernier caliper?

The caliber or vernier caliper is made up of a fixed part and a mobile part that moves. It also has an internal clamp, with which the external diameters are measured, and another external one, with which the internal ones are measured. Finally, among the parts of the foot, we find that in the rear part it has a depth probe, with which the blind holes are measured.

Fixed part parts:

• Primary measurement scale, which can appear in millimeters, inches, or both.
• The fixed mouth of both sets of jaws.
• In the digital caliper there is also the LCD screen on which the measurements are displayed.

Moving part parts:

• The mobile mouths of the two sets of jaws.
• depth sounder
• Vernier or auxiliary scale.
• Brake to block the opening of the caliber.

How to use the gauge

If you want to find out how the caliper works, you should know that it is a very simple tool, as the calipers have two sets of pliers of different sizes, as well as a depth gauge. The larger set of calipers is used for outside measurements, while the smaller ones are for inside, and the probe for depth.

In this sense, to measure with the large calipers, the object must be positioned on the inside and not on the ends, which have a bevel. This is because the bevel can falsify the measurement. On the other hand, the interior measurements are taken with the small calipers, which must be placed between the two interior walls and opened until they rest on the interior of the object.

Also, the small calipers can be used to find step measurements. To do this, the vernier caliper must be placed on the upper part of the step and opened until the clamp is flush with the descending part.

Finally, to measure the depth, simply rest the bottom of the gauge on the hole and open the probe until it touches the bottom.

On some occasions, when making a measurement, you will find a certain gap between the main measurement and the one that appears in the vernier. If this happens, you will only have to add the difference between the two measurements to obtain a verification measurement. That is, if the main measure is 9 mm and the vernier measure is 0.8 mm, the precise result will be 9.8 mm.