When we talk about reading a micrometer, we are talking about mechanical micrometers, since with digital a computer is responsible for making the calculations and display them on the screen. To better explain how a micrometer is read, let’s see an example.
How to Read a Micrometer
Suppose we have the following measurement
To determine the value of this measurement, we must first observe the fixed drum, in this case, the left part of the image. We see number 15. From number 15 to the next hairline that is at the top there is one millimeter. From 15 to the hairline that is in the bottom half a millimeter.
We see that the mobile drum (right part) cuts the fixed drum a little after the 16th and after the hairline that marks the 0.5. So we are talking about a measurement of 16.5 mm. To continue with the precision, we go to see the mobile drum.
We see that in the scale, the first hairline coincides with the average line of the fixed drum. This means that we are talking about 0.01 mm more. Therefore the measurement of this micrometer gave us 16.51 mm.
1. Reading and interpretation of micrometer in hundredths of a millimeter
The micrometer is a portable measuring instrument is not very versatile, but it is of good precision when used correctly.
This instrument is not very versatile, because its measuring range is limited to one inch. Additionally, there is a relatively large loss of time in the tasks of configuration and approximation of the measurement to be taken.
Before use: adjust the micrometer
I am trying to “zero the micrometer” the operation to adjust the instrument that is to test it with a known measure, for example, the zero or another measure, with the help of a pattern, and helped by a suitable key, to align the ‘cylinder reference line’ with the zero marks (0) of the drum. Of course, you have to use the “ratchet” to close. Also, the same number of revolutions of the ratchet must be repeated in each measurement. See the process of measuring the page: use of the micrometer.
The operation of the micrometer
Drum in partial section to show the divisions of a millimeter and half a millimeter
A pair of the male / female thread has the pitch and calibrated settings. In solidarity with the spindle is the drum and equidistant lines mark its circumference. A complete revolution of the drum (and the spindle) produces an advance equal to the thread pitch. This spindle usually has a useful thread length slightly greater than 25 millimeters.
In the cylinder, there is a graduation that controls the advance of the drum/spindle. In general, these marks are 1 millimeter from the neighbors. There are also marks to control the advance of half a millimeter (0.5 mm – in this example, below the reference line), since, as we have seen, a full turn of the drum produces the advance of 0.5 mm.
The micrometer resolution
By definition: “resolution” is the “smallest difference between the indications of a visualization device that can be perceived significantly,” is the smallest measure that can be referenced by a measurement instrument, for example.
In the centesimal micrometer, the resolution is obtained by dividing the thread pitch of the micrometer spindle by the number of divisions of the drum (Resolution = thread pitch of the micrometer spindle/number of divisions of the drum) or Resolution = 0.5 mm / 50 = 0.01 mm.
The centesimal resolution
The configuration most commonly found in metalworking workshops is the micrometer screw with a pitch of 0.5 mm and the drum with 50 divisions. In this way, by rotating the micrometer spindle each mark of the drum passes through the “reference line” will indicate that the measurement tips move away (or approach) 0.01 mm (one-hundredth of a millimeter).
2. Reading and interpretation in thousandths of a millimeter resolution
This text will exclusively address the interpretation of the micrometer part of the micrometer. If you are not yet instructed in the use, reading and interpretation of the centesimal part of the micrometer, interact with these pages before proceeding.
This text supposes that you are familiar with the terminology of the components of the Micrometer <- if necessary, do a review by clicking here and with the reading of the graduated rule or scale, in millimeters <- review by clicking here.
The operation of the micrometer of a thousandth of a millimeter
Drum in partial section to show the vernier that divides the hundredth of the inch into ten.
The main difference of this configuration is that it has ten lines parallel to the ‘reference line’ marked on the cylinder. Another difference is in the position of the marks of half a millimeter.
The resolution of the micrometer millesimal, the reading of the nónio
In the centesimal micrometer, the resolution was obtained by dividing the pitch of the micrometer spindle by the number of divisions of the drum (resolution = pitch of the micrometric screw thread/number of divisions of the drum) or resolution = 0.5mm / 50 = 0.01mm
In the micrometer, the smallest difference between the indications is divided by ten by a marked vernier in the cylinder. In this way, the resolution becomes: Resolution = 0.01mm / 10 = 0.001mm.
3. Reading and interpretation of the micrometer in ten-thousandths of an inch: reading the vernier
Drum in partial section showing the vernier dividing the thousandth of the inch by ten.
The main difference of this configuration is that it has ten lines parallel to the “reference line” engraved on the cylinder.
The resolution of the micrometer ten-thousandth, the vernier reading
In the thousandths of an inch micrometer, the resolution was obtained by dividing the thread pitch of the micrometer spindle by the number of drum divisions (Resolution = thread pitch of the micrometer spindle/number of drum divisions) or Resolution = 0.025in / 25 = 0.001 in.
In the micrometer of ten-thousandths of an inch, the smallest difference between the marks is divided by ten by a vernier engraved in the cylinder. In this way, the resolution becomes: Resolution = 0.001inm / 10 = 0.0001in.
The operation of the micrometer in thousandths of an inch
Drum in partial section to show cylinder marks
A complete revolution of the drum (and the spindle) produce an advance equal to the pitch of the thread. The thread of this spindle usually has the useful length of one inch, and the step 25 thousandths of an inch.
In the cylinder, there is a graduation that controls the advance of the drum/spindle. The inch (or 10 tenths) is divided into nine main lines, the distance between them is one-tenth of an inch, these lines have numbers to help reading, the tenths of an inch are divided into three marks that control the advance of twenty-five thousandths inch (0.1 / 4 = 0.025 in). This means that each time the drum shows a new mark, the spindle moved the equivalent to twenty-five thousandths of an inch (0.025in).
The resolution of the micrometer in thousandths of inches
The configuration most commonly found in the metalworking workshops is the micrometer screw with the step of 0.025 in and the drum 25 divisions. In this way, by rotating the micrometer spindle, each mark of the drum that passes through the “reference line” will indicate that the mobile stop moves away (or approaches) 0.001 in (one-thousandth of an inch).
4. Reading and interpretation of the caliber in millimeters – vernier or vernier 0.05 mm
The caliber with vernier, also known as gauge or caliper, is a measuring instrument equipped with a scale and a cursor that slides in it. The cursor has recorded a second scale called vernier, also known as a vernier.
At one end of the scale, there is a gag with a face perpendicular to it. In the cursor there is also a jaw with faces perpendicular to the scale, when these faces are in contact, the zero marks (0) recorded on the cursor is aligned with the zero marks (0) recorded on the scale.
O Caliber or King’s Foot was conceived to take external linear dimensions by contact. With less accuracy, it can also measure internal dimensions, depths and highlights.
To take external measurements, position the object to be measured in contact with the lateral face of the fixed jaw, the closest possible to the scale, without touching it, and gently slide the cursor, with the thumb, until the face of the jaw mobile touch the object, without hitting and without exerting excessive pressure. The reading of the whole value in millimeters is taken by comparing it with the position of the zero marks (0) of the vernier, the cursor, with the marks engraved on the fixed scale, the decimal part is observed when the vernier is aligned with a mark of the fixed scale. See the Noni Simulator page to understand this method better.
This virtual caliber is a replica of the metrology instrument used in the metal-mechanic industry.