Micrometer - a device with a very high accuracy for measuring the size of parts. It is used where scrupulous adherence to dimensions is necessary in the manufacture of products. The accuracy of its measurements is one thousandth of a millimeter (micrometer or micron), and the error is only 2 to 50 microns. This is much more accurate than that of the same vernier caliper. To imagine such values more clearly, it should be remembered that the thickness of a human hair is about 40 microns, and the diameter of an erythrocyte is 7 microns.
It became known how to use a micrometer in the 19th century, or rather, in 1848. It was then that a patent was issued in France for this measuring device to the inventor Jean-Louis Palmer, although the idea of using a screw pair, on the basis of which the operation of the micrometer is based, is known since the 16th century. First, a screw pair was used in military affairs (cannon shooting), and then in topographic and geodetic instruments. These days, how to use the micrometer correctly, is known, perhaps, only to a narrow circle of specialists (for example, turners who process extremely precise surfaces). But knowing how to take measurements with this tool will clearly not hurt any person, especially those dealing with technology.
The principle of operation of the micrometer
The main part of the micrometer is the bracket. It is made stationary, and all other parts of the device are attached to it: the heel (which serves as a fixed stop during measurements), stem, micrometer screw, ratchet drum and stopper. The stem on which the scale is located is a tube fixedly connected to the bracket. The scale consists of risks applied along the stem and strokes perpendicular to it. Below risks, strokes are applied at a distance of 1 mm, and above the risk - 0.5 mm. Nowadays, you can find an electronic micrometer on which all values are displayed. The advantage of such a device is that it can always be reset to zero with just the touch of a button. To achieve greater accuracy, it is better to do this before using the micrometer.
The movable stop of the device is a micrometer screw. A stopper is used to clamp it in position. A drum is worn on the stem, which is a conical surface divided by strokes into 50 equal parts and worn on the stem. One revolution of the micrometer screw, and therefore the drum, leads to a 0.5 mm movement along its axis. Thus, one rotation of the drum per division is 1/50 of 0.5 mm or 0.01 mm. To prevent deformation of the part, a ratchet is used to limit the pressure on it of the micrometer screw.
How to use a micrometer when taking measurements
- The part, the dimensions of which must be measured, is placed between the heel and the micrometer screw. Rotate the drum to position the spindle as close to the part as possible.
- Carefully slide the spindle into contact with the measured part. Twisting should be done only by holding on to the thread located at the end of the rotating drum. When the measuring end rests against the part, the scrollable part of the drum along the way will emit a sound (click). After the third click, the rotation must be stopped.
- Using Vernier, measure the part in millimeters, which is read by the horizontal index bar located on the scale of the stem.
- Determine the total dimensions of the measured part.
- Release the part by rotating the drum in the opposite direction.
In conclusion of the article on how to use a micrometer, it should be noted that using this simple but reliable device is not difficult, and the ability to determine the exact dimensions of especially small parts can sometimes be very useful.