The caliper belongs to the class of universal measuring instruments of high accuracy. This device is designed to determine the external and internal dimensions of small parts, hole depths and other parameters. Knowing how to measure with a caliper, you can easily establish the linear values of any objects, including threaded joints on hardware.
Features of using caliper
Convenience and ease of use of this tool determine its widespread use not only in the manufacturing sector, but also at home. There are three types of calipers: vernier, dial and digital, differing in their design. The first option is most popular. Such a tool has a mechanical structure, so there is nothing to break. With careful handling (it is necessary to protect the device from deformation and rust), its service life is practically unlimited.
The Vernier scale allows measuring with a caliper as a micrometer, that is, up to tenths of a millimeter. The tool design provides for the possibility of fixing the measured object from both the outside and the inside, so that the probability of error is reduced to zero.
Structural elements of devices
To understand how to measure with a caliper, you need to understand its design. The instrument got its name in honor of the bar, on which the main scale is located. An additional scale is the nonius, designed to determine tenths or hundredths of a millimeter if necessary to obtain the most accurate results.
The design of a mechanical vernier caliper consists of:
- rods with a main scale;
- movable frame with Nonius scale;
- jaws for measuring internal surfaces;
- jaws for measuring external surfaces;
- depth gauge rulers;
- screws for fixing the frame.
Some models have a dual scale that allows you to measure with a caliper in both millimeters and inches. The remaining structural elements, as a rule, have no differences.
How to measure the outer surfaces with a caliper
To obtain accurate data on the external dimensional parameters of the object, it must be fixed using the lower jaws of the tool. This operation is carried out by preliminary spreading the jaws a little more than the size of the measured part, and then moving them all the way to the surface of the product. After the lower lips of the caliper are firmly fixed on the outer surfaces, the control point on the movable scale will occupy a certain position on the main scale and will indicate the size of the part.
How to measure the inside diameter of a part with a caliper
Before performing this operation, the elements of the device are shifted to the stop, after which the jaws are placed in the hole to determine the distance between the internal surfaces. Then they are bred to the stop in the wall and fixed in this position. Knowing how to measure the diameter with a caliper, you can measure the internal planes of any other shape.
Depth determination
This operation is performed using a depth gauge. The face of the caliper rest against the top of the part, and the depth gauge is led into the hole until it stops. The depth of the measured product will be displayed on the main scale.
Measurement of threaded connections
Determining the dimensions of the internal and external surfaces of parts is a simple operation and familiar to many from school labor lessons. But not everyone knows how to measure thread with a caliper.
This procedure may be required in different cases, for example, if the bolt is non-standard or it is necessary to measure the fastener without removing the threaded connection. The following are examples of how to use a caliper to measure bolts and nuts in various situations.
- Determining the length of the bolt screwed into the part. This operation is performed using a depth gauge. The height of the bolt head, the thickness of the washer (if any), the thickness of the intermediate part and the height of the part of the bolt shaft protruding from the back of the part are successively measured. The obtained values are summarized, after which the size of the fastener is determined using special tables of correspondence of the lengths of the bolts and the dimensions of their turnkey heads.
- Determination of thread diameter. This parameter is measured by protrusions, not by thread grooves. A bolt is placed between the caliper lips in an upright position and measurements are taken. If the obtained indicator does not correspond to the standard sizes indicated in the table, the depth of the thread is measured using a depth gauge. After that, the double value of the second is subtracted from the first result and thus it is determined whether a part of the thread profile has been cut. Damaged hardware must be replaced.
- Measurement of the thread diameter of a bolt completely "recessed" in the part, without dismantling the connection. For this, an external caliper scale is used, by means of which the dimensions of the head and the diameter of the circumference of the protrusions are established. Further, the part is identified using tables.
- Thread pitch measurement. Using a caliper, determine the height of the bolt rod and its outer diameter, and then count the number of threaded turns on it. The ratio between these indicators will be the tangent of the angle of inclination of the thread.
- Measuring the diameter of the thread of nuts. This operation is carried out using the internal jaws of the caliper. When using some models of tools, the thickness of the sponges, which is indicated on the bar, must also be added to the obtained value.
Reading
First of all, it should be noted that the accuracy of the readings depends on the cleanliness of the surfaces of the part, therefore, before measuring with a caliper, it is necessary to remove dirt and grease from the products.
Having fixed the jaws of the tool on the part, on the main scale find a control stroke located on the left in the immediate vicinity of the zero vernier stroke. This will be the size of the measured surface in millimeters.
Further readings are read in fractions of a millimeter. This operation is performed by finding the division closest to the zero stroke and coinciding with the stroke on the bar scale. As a result of adding up its serial number and the division price of the nonius, the required indicator is calculated. For the most popular caliper models, the division price is 0.1 mm.
The total value of the instrument readings is obtained by summing the results in whole millimeters and in fractions of a millimeter.
Caliper Operating Rules
In order for the measuring tool to serve faithfully for many years, it is necessary to observe simple rules for its operation and storage. First of all, mechanical damage that may occur as a result of a fall or force impact should be avoided. In addition, during the measurement of parts, it is impossible to prevent the misalignment of the lips of the caliper. To prevent this from happening, they must be fixed in a certain position on the measured part using the locking screw.
The device should only be stored in a soft case or hard case. The second option is preferable, as it can provide protection against accidental deformations. The place for storing the caliper must be selected so that sawdust from various materials, dust, water, chemical mixtures, etc. do not fall there. In addition, the risk of heavy objects falling on the tool must be excluded.
After each use, the caliper must be thoroughly wiped with a clean, soft cloth.
Naturally, one should not forget about observing the safety rules when operating this device. At first glance, it does not pose any threat to health, but this is not entirely true. The fact is that the ends of the jaws for measuring the internal dimensions are quite sharp, so you can easily hurt yourself with careless handling. The rest of the tool is completely safe.