Twentieth caliber: what is meant and how is it used?
The caliper is a length measuring instrument formed by a fixed graduated part (millimeters and / or inches) and by a movable vernier that includes the vernier, another additional graduated scale with 20 millimeter notches : for this reason it is usually called a caliper twentieth .
The caliber was created in 1631 by the French mathematician inventor
Pierre Vernier , who perfected the original idea of the
vernier , that is the part that reads the smallest measures (conceived by Pedro Nunes - 1542). This is why the vernier caliber is also called
the Vernier caliber .
In this guide we will see together what a
vernier caliper is and how it should be read. I'll show you a system that is valid for both the twentieth and fiftieth caliber.
What is a gauge?
The caliber is an instrument made of mechanically worked stainless steel and consisting of a (fixed) ruler where a (mobile) cursor called vernier slides.
With the gauge you can measure:
- external dimensions (width, length, thickness, distance between 2 surfaces, external diameter);
- internal dimensions (internal diameter, internal distance between 2 surfaces);
- distances between two levels of an object (such as the depth of a cavity or hole).
What is a vernier caliper for?
The
vernier caliper can measure the distances between 2 points parallel to the axis of the instrument: in this way it is possible to calculate the lengths, depths, distances between plane faces and diameters.
The gauge has a
resolution of the following:
- decimal caliber,
- twentieth caliber,
- fiftieth caliber,
- centesimal caliber.
The decimal caliber reads up to tenths of a millimeter, the twentieth caliber reads up to 1/20 of a millimeter (i.e. 0.05 mm), the fiftieth caliber reads up to 0.02 mm and the centesimal, up to 1/100 mm ( 0.01 mm).
How is the vernier caliper made?
The vernier caliper is made up of two graduated rulers that slide in an axial direction one over the other. These rules are equipped with appendages (beaks) which act as references or stops.
The main graduation, i.e. the measuring range, is called the fixed part or body. The mobile part that houses the vernier is called the slider.
The vernier has a graduated line used to evaluate the fractions of the unit of measurement.
Types of vernier calipers
How many types of caliber are there? It depends on the size you want to measure:
- gauges for outdoors;
- gauges for interiors;
- depth gauges;
- universal calibers.
How is the vernier caliper used?
When the jaws are far away and touch the surfaces to be measured, the cursor slides on the fixed part.
Sliding is carried out by means of a roller or a spring-operated lever, which locks the position at the measured value.
Before measuring, it is necessary to evaluate the
range of the instrument , i.e. the maximum measurable size. You must know the resolution with which you want to take the measurement.
The most common universal caliber is the twentieth one, with a minimum resolution of 5 hundredths of a millimeter.
The second step is to identify what size you want to measure:
- if the dimension is external, the main jaws must be used (they have flat surfaces facing inwards);
- if the dimension is internal, the jaws of the upper part must be used (they have flat surfaces facing outwards);
- if the measurement is of a depth, then the outgoing rod (lower part of the gauge) must be used.
How to measure external dimensions with a caliper?
The first operation to do to measure a piece is to open the jaws of the instrument by sliding the cursor on the fixed body in order to have enough space to "embrace" the area under investigation.
Then squeeze the beaks until the surfaces of the beaks and the object to be measured are parallel; in reality with the caliber objects of circular, ellipsoidal or other shape are also measured, but we will see in detail how to do it in a few lines.
How to measure external dimensions with a caliper?
The measurement of internal dimensions with the caliper is done with the upper jaws, which show the parallel surfaces facing outwards.
The jaws must be inserted inside the hole or between the two parallel surfaces to be measured.
How to measure depth with a caliper?
Depth measurements are made with the rod hooked to the caliper slider, moved outwards, it makes the rod come out of the fixed body.
The depth measurement is carried out by placing the lower part on a surface that acts as a reference; then the slide is pushed down until the end of the rod reaches the second surface.
How do you read the vernier caliper?
Caliber reading in the international system (metric mm)
The reading of the measured length is carried out in two stages:
- read the length in millimeters at the 0 of the vernier;
- read on the vernier the value corresponding to the coincidence of the two vertical segments.
Caliber reading in the Anglo-Saxon system (inches)
You must have a caliber with metric and Anglo-Saxon units of measure. The inch scale is engraved on the top of the instrument and the vernier you will need to use is the one at the top.
How to use the digital caliper?
Digital calipers , increasingly popular, show the measurement on a display that usually has a resolution of 0.01 mm.
In a digital caliper there are keys that allow you to turn on and off, reset, set the zero and save the measurements.
What is the difference between micrometer or caliper?
The
micrometer is a contact measuring instrument like the caliper, but is capable of having a higher accuracy.
The reduction of measurement errors (uncertainty) is guaranteed by
the Abbe condition .
