Frequently used in mechanics and plumbing, the vernier caliper displays the exact measurement of a part. Depending on the model, its accuracy varies from 1 / 10th to 1 / 50th mm. Provided you control its use.
Practical advice
The caliper is a precision instrument. It must be taken very carefully and put back in its box after use. Wipe ruler and slider with an oily cloth, soaked in tallow, or spray without excess with silicone grease.
To enter and exit a room between the beaks, do not force under penalty of damaging or wear the beaks prematurely. Closed, we must not see the light at their junction.
Measure the thickness or depth of an object
The vernier caliper is an instrument used to measure the thickness or depth of small objects as well as the inside and outside diameters of tubes. While the precision of a tape measure is of the order of a millimeter and that of a ruler of half a millimeter, the accuracy of the caliper is, depending on the model, 1 / 10th, 1 / 20th, or 1 / 50th of a millimeter.
● A vernier caliper consists of two graduated parts: a fixed part (ruler) and a moving part (slide) that can be locked on the ruler using a clamping wheel.
● The ruler, graduated in millimeters, is equipped with a two-part head, consisting of a fixed spout and a movable spout. Depending on how they are used these nozzles measure the inside or outside of a room (see diagram).
● The slider is the exact symmetry of the ruler’s head. It is equipped on its front face with a graduated ruler, the vernier *, and on its rear face a depth gauge. The set can be moved on the ruler.
Caliper, user manual
When the vernier caliper is closed, the heads are in contact. The zero graduations of the ruler and the vernier are incomplete coincidence.
Note that only the number of graduations of the vernier differs according to the caliper scale. On the other hand, whatever the scale (1 / 10th, 1 / 20th or 1 / 50th) the measurement principle remains the same. Simply open the spouts by sliding the slide, place the piece against the fixed spout, and gently bring the movable spout back into contact with the room.
Reading the dimension in three steps
The distance between the graduations of the vernier is smaller than that of the rule. On the latter, the graduation is at scale 1, while the graduation on the vernier is a function of the scale of the instrument. In our example of calipers at 1 / 50th, the graduations are two in two. The reading of the dimension is then done in three stages:
- The first digit to remember is on the ruler, before the 0 marks of the vernier (A). In our case, between 23 and 24 mm. We retain 23 mm.
- We then look at the vernier for the exact coincidence between graduation of the vernier and one of the rules. In our case, it is the third graduation (rep B) between 9 and 0. We, therefore, retain the 6 (or 0.06 mm).
- On the vernier, note the graduation (C) located before the value retained above. The nine is then retained (i.e., 0.9 mm). The result is the sum of the three marks (A, C, B), ie 23 + 0.9 + 0.06 = 23.96 mm
* Device invented by the Portuguese mathematician Pedro Nuñes (1492-1577) and distributed by the French geometer Pierre Vernier (1580-1637).
Caliper: the choice of precision
Depending on the desired accuracy, use a vernier caliper at 1 / 10th or 1 / 20th or 1 / 50th (from left to right). The quality of the production is related to the precision of the tool.
Outdoor measurement
Depending on the desired accuracy, use a vernier caliper at 1 / 10th or 1 / 20th or 1 / 50th (from left to right). The quality of the production is related to the precision of the tool.
Internal measurement
In-depth measurement
Measuring a cylinder
The inside measurement of this cylinder requires a 1 / 50th instrument. The tip of the beaks measures exactly 10 mm. Add this value to the measured dimension.
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