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How to use a micrometer to measure small parts

Micrometer - a very high precision instrument for measuring the size of parts. It is used where there is a need for scrupulous compliance with the dimensions 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 calipers. To imagine such quantities more clearly, it should be recalled that the thickness of a human hair is about 40 microns, and the erythrocyte diameter is 7 microns.

About how to use the micrometer became known in the XIX century, or rather - in 1848. It was then in France that a patent was issued for this measuring device to the inventor Jean-Louis Palmer, although the idea of using a screw pair based on the principle of the micrometer is known Since the XVI century. At first the screw pair was used in military affairs (shooting from guns), and then in topogeodesic instruments. Today, how to use the micrometer correctly is known, perhaps, only to a narrow circle of specialists (for example, turners, processing particularly precise surfaces). But knowing how to perform measurements with this tool will clearly not harm anyone, especially those dealing with technology.

The principle of the micrometer

The main part of the micrometer is the bracket. It is fixed, and all the other parts of the device are attached to it: the heel (which serves as a fixed stop for measurements), the stem, the micrometric screw, the ratchet drum and the stopper. The stem on which the scale is located is a tube fixed to the bracket. The scale consists of the risks applied along the stem and perpendicular strokes. Below, the risks of strokes are plotted at a distance of 1 mm, and over the risk - 0.5 mm. In our time, you can find an electronic micrometer, on which all values are displayed. The advantage of this device is that it can always be reset with just one click. To achieve greater accuracy, it is better to do this before using the micrometer.

The movable focus of the device is a micrometer screw. A stopper is used to clamp it in the desired position. A drum is placed on the stem, which is a conical surface, divided by strokes into 50 equal parts and put on the stem. One revolution of the micrometer screw, and consequently of the drum, leads to displacement along its axis by 0.5 mm. Thus, one turn of the drum per division is 1/50 of 0.5 mm or 0.01 mm. To avoid deformation of the part, a ratchet is used to limit the pressure on the micrometer screw.

How to use a micrometer when performing measurements

  1. A detail, the dimensions of which need to be measured, is placed between the heel and the micrometer screw. Rotating the drum, set the spindle as close to the part as possible.
  2. Carefully slide the spindle until it touches the part to be measured. Twisting should be done only by holding on to the thread placed on the end of the rotating drum. When the measuring face rests against the part, the scrolling part of the drum will sound (click) on the way. After the third click, the rotation should be stopped.
  3. Using a vernier measure the parts in millimeters, which is read by a horizontal index stroke located on the stem scale.
  4. Determine the overall dimensions of the measured part.
  5. Release the part by rotating the drum in the reverse direction.

At the conclusion of the article on how to use a micrometer, it should be noted that using this simple but reliable instrument is not difficult, and the ability to determine the exact dimensions of particularly small parts can sometimes be very useful.

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