Micrometer

A micrometer, often also called a micrometer screw gauge, is an instrument used to measure various types of objects with remarkable accuracy reaching up to 0.01 mm. The principle of operation is based on a vernier and the use of a micrometer screw.

The micrometer screws are very precisely manufactured and connected to the micrometer thimble around which there is a special scale called a vernier. A ratchet is also connected to the thimble, ensuring an adequate, even pressure of the jaws. The micrometer jaws themselves consist of fixed jaws and a spindle, i.e. a movable jaw which is most often an extension of the micrometer screw.

The basic scale consists of a line separating two divisions. One of them is placed above the line and the other below, but it is shifted by 0.5 mm in relation to the upper scale. Around the thimble is the aforementioned vernier scale. When the jaws are adjacent to each other, the edge of the thimble is aligned with the scale mark, and the zero mark of the vernier line is aligned with the dividing line of the scale, then the reading is 0.0 mm. If we want to measure an object, we have to place it between the jaws and slightly tighten the thimble.

After this action, we have to tighten it using the knob until we hear the click of the pawl of the ratchet. The place of the required reading is shown by the edge of the thimble, and the point on the vernier scale, which at this point is aligned with the line, on the horizontal (basic) scale gives us an additional reading. Based on the sum of these two readings, we obtain a complete very accurate main reading.