What is a measuring tool? Measuring tool Tools for technical measurements

2.1.4. Mechanical and lubrication work Question 33. What are the requirements for removing parts, assemblies and assemblies from the vehicle and installing parts, assemblies and assemblies on it? Answer. Parts, assemblies and assemblies removed from the vehicle should be installed on special stable stands, and long parts - on racks.

8.3.5. CONTROL AND MEASURING INSTRUMENTS Initially, only an ammeter was used on cars (Ford-AA, GAZ-AA, ZIS-5). Then a fuel level meter appeared (GAZ-M-1, ZIS-101). The growth of measuring equipment began to be observed on domestic cars only in

Measuring tools Firstly, you will always need various measuring tools and devices to apply the necessary markings:? folding meter, ruler and tape measure;? scribers;? two types of surface planers;? a metal square having a right angle, and squares with

In production

Measuring tool - a tool designed to measure linear objects.

Simple measuring tools

Measuring Ruler

Measuring Ruler is the simplest geometric measuring instrument; the ruler has marked divisions that are multiples of the unit of measurement of length (centimeter, inch), which are used to measure distances.

Measuring tape

Vernier tool

Vernier tool - a tool for measuring and marking linear dimensions:

a) holes and shafts (vernier calipers);

b) depths and lengths (vernier height gauge, depth gauge);

c) gear teeth (vernier gauge).

The accuracy of its measurement is tenths of a millimeter.

Calipers

Vernier calipers are a universal tool designed for high-precision measurements of external and internal dimensions, as well as hole depths.

2) movable frame

3) rod scale

4) sponges for internal measurements

5) sponges for external measurements

6) depth gauge ruler

8)screw for clamping the frame

Vernier depth gauge

A vernier depth gauge is used to measure the depths of recesses, grooves, ledges, etc. It differs from a caliper in that it does not have movable jaws on the rod.

Height gauge

Meter. Designed to measure the depth of recesses and depressions.

Goniometer

Protractor - a goniometer device designed to measure geometric angles in various designs(external and internal corners of products.), in parts and between surfaces (mainly by contact method) and between distant objects (optical method). The measurement is made in degrees, based on a bar scale, a bar-circular scale (with a mechanical pointer or pointer), a vernier or electronically, depending on the type of device.

The design of goniometers allows marking work on a plane.

Micrometer instrument

Micrometer smooth

A smooth micrometer is a tool for measuring external linear dimensions.

The readings on the smooth micrometer scales are taken in the following order:

· on the stem scale, read the mark near the line closest to the end of the drum bevel;

· on the drum scale, read the mark near the stroke closest to the longitudinal stroke of the stem;

· add both values ​​and get the micrometer reading.

For convenience and to speed up readings, there is a smooth micrometer with digital display.

Thread micrometer

A thread micrometer is used to measure the average diameter of metric and inch threads and has the same device as a conventional micrometer, but differs from the latter only in the presence of a hole in the heel and spindle, into which special replaceable inserts of various shapes are inserted: prismatic, conical, flat, spherical.

a – general view,

b – inserts,

c – measurement techniques;

1 – heel,

2 – spindle,

3 and 5 – threaded inserts,

4 – measured part

Each micrometer is supplied with sets of such inserts, which are placed in a case in pairs and are intended for measuring threads in increments of 1 -1.75; 1.75-2.5, etc. The profile angle of the inserts must correspond to the profile angle of the thread being tested.

The average diameter of the thread of part 4 is checked with a prismatic insert 5 inserted into one of the threads; on the other hand, a conical insert 3 is inserted perpendicular to the thread axis into the thread cavity. The measurements are taken according to

micrometer scales.

Micrometric depth gauge

Designed to measure the depth of grooves, holes and the height of ledges.

Micrometric depth gauges have the same structure as micrometers, only instead of a bracket there is a base (90x12 mm) 1 with a measuring rod 2. The base and measuring rod are hardened. Each micrometric depth gauge is equipped with three replaceable rods with measurement limits of 0-25 mm; 25-50 mm; 50-75 mm; 75-100 mm.

1 - base, 2 – rod

Micrometric bore gauge

A micrometric bore gauge is a device with which more accurate measurements of holes are made using the absolute method; it also has replaceable extensions.

4)Tool with dial gauge:

Wall gauge (thickness gauge)

A wall gauge is an industrial device designed for monitoring and measuring external and internal dimensions, wall thickness of workpieces, and grooves. A wall gauge is convenient for measuring the wall thickness of pipes. The measuring range of the wall meter is from 25 to 50mm. The division value is 0.1mm to 1mm, the measurement depth is 160mm, the smallest hole diameter is 20mm. The permissible error limits are ±0.10. The indicator wall gauge is made of carbon or stainless steel. An indicator wall gauge is a measuring device used to measure linear dimensions using the contact method. The type of measurement is absolute.

The indicator wall gauge consists of a fixed upper frame (body) with a handle, a movable lower frame, which is pressed against the fixed one using a return spring. A dial indicator is attached to the upper frame, the measuring rod of which rests against the horizontal protrusion of the lower frame. When the lower frame is pressed, the protrusion of the lower frame moves the indicator rod. The movement of the measuring rod is converted by the gear mechanism of the dial-type measuring head into the movement of the arrow of the measuring head. The count is taken from the head scales: main and auxiliary.

Indicator bore gauge

An indicator bore gauge is a device for internal measurements. Indicators are intended for relative or comparative measurement and verification of deviations from the shape, dimensions, as well as the relative position of the surfaces of the part. These tools are used to check the horizontal and vertical position of the planes of individual parts (tables, machines, etc.), as well as the ovality, taper of shafts, cylinders, etc.

1-dial indicator

6-tee bore gauge head

8-dimension rod

9-lever

10-rod

11-coil spring

In addition, indicators are used to check the runout of gears, pulleys, spindles and other rotating parts. They also come in clock and lever types.

The most common are dial indicators, which in combination with other instruments (bore gauges, depth gauges, etc.) are used to measure internal and external dimensions, parallelism, flatness, etc.

Hour indicator

It consists of a housing 4, in which a measuring rod 7 (spindle) with a gear rack cut on its surface passes through the entire long sleeve 6.

5) Limit calibers

Measuring plugs

For checking hole diameters. The non-go side differs from the go side by the shorter length of the measuring part or the presence of a groove at the handle or insert

Measuring brackets

For checking shaft diameters and lengths.

6)Templates

Template - a plate (pattern, stencil) with cutouts along the contour of which drawings or products are made or a tool for measuring dimensions.

For measuring external and internal angles. Checking the deviation from the angle is carried out by observation “through the light”.

Pattern rulers

The ruler is designed to check straightness using the light slit method “through the light” and is used in patterning, plumbing and control operations.

Template rulers are made from tool carbon or alloy steel with high precision and have thin working edges, called ribs or blades, with a radius of curvature of 0.1-0.2 mm, thanks to which deviations from straightness can be very accurately determined.

Surface plate

Verification plate - a metal plate with standardized flatness and surface cleanliness: designed to control the flatness of parts and marking work; used as a mounting surface during assembly, measurements and verification.

Squares

Flat pattern squares are designed to check right angles (90°) and are used in metalworking, assembly and pattern work to control the mutual perpendicularity of parts.

Radius patterns

Radius templates are designed to estimate the radii of convex and concave surfaces. Three sets of radius templates are made. Each set contains plates for control of both outer and inner radii. The design of the set's clip allows for free replacement of the template, as well as regulation of the smoothness of their rotation on the axis.

Threaded templates

Thread templates are used to determine the pitch and angle of the thread profile. Threaded templates are steel plates with teeth located along the axial profile of the thread. Thread templates are available for measuring inch or metric threads.

To determine the pitch and profile angle of the thread, the thread template is combined with the thread of the part being tested so that the teeth of the template fit into the grooves of the thread. Next, based on the tightness of the fit of the edges of the threaded template to the thread, the correspondence of the pitch and angle of the thread profile to the pitch and angle of the profile of the threaded template is determined.

The choice of measuring instruments when checking the accuracy of parts is one of the most important stages in the development of technological control processes.

The basic principles for choosing measuring instruments are as follows: the accuracy of the measuring instrument should be quite high compared to the specified accuracy of the measured size, and the complexity of measurements and their cost should be as low as possible, ensuring the most high performance labor and economy.

Insufficient measurement accuracy leads to the fact that some suitable products are rejected (type I error); at the same time, for the same reason, another part of the actually unsuitable product is accepted as acceptable (error of the second type).

Excessive measurement accuracy, as a rule, is associated with an excessive increase in the labor intensity and cost of product quality control, and therefore leads to an increase in the cost of production.

When choosing measuring instruments and methods for monitoring products, take into account

• permissible error of the measuring instrument;
• scale division price;
• sensitivity threshold;
• measurement limits, weight, overall dimensions, workload, etc.

The determining factor is the permissible error of the measuring instrument, which follows from the standardized definition of the actual size as well as the size obtained as a result of measurement with a permissible error.

The simplest way to select measuring instruments is based on the fact that the accuracy of the measuring instrument must be several times higher than the manufacturing accuracy of the part being measured. When monitoring the accuracy of technological processes by measuring the dimensional accuracy of parts, it is recommended to use measuring instruments with a division value of no more than 1/6 of the manufacturing tolerance.

The value of the permissible measurement error depends on the tolerance, which is associated with the nominal size and with the quality of the size accuracy of the controlled product. The calculated values ​​of the permissible measurement error in microns are given in standard tables.

2. Instrumentation

Tools with a linear vernier include calipers, height gauges, and depth gauges. The basis of a vernier tool is a ruler - a rod with divisions marked on it; this is the main scale. A frame with a cutout moves along the rod, on the inclined edge of which there is a vernier (auxiliary) scale.

Calipers (Fig. 2) is intended for measuring linear dimensions (diameters, depths, widths, thicknesses, etc.). On a length of 9 mm of the frame (vernier), corresponding to 9 divisions of the bar, 10 equal divisions are applied. Thus, each vernier division is equal to 0.9 mm.

Rice. 2.

If you place the frame so that the sixth stroke of the vernier is opposite the sixth stroke of the rod, then the gap between the jaws will be equal to 0.6 mm (Fig. 3, A).

Rice. 3. A – for size 0.6 mm; B – for size 7 mm; B – for size 7.4 mm

If the zero stroke of the vernier coincides with any stroke on the rod, for example the seventh, then this division indicates the actual size in millimeters, i.e. 7 mm (Fig. 3, B).

If the zero line of the vernier does not coincide with any line on the rod, then the nearest line on the bar to the left of the zero line of the vernier shows an integer number of millimeters. Tenths of a millimeter are equal to the ordinal digit of the vernier stroke to the right, not counting the zero, which exactly coincided with the stroke of the rod - the main scale (for example, 7.4 mm in Fig. 3, B).

In addition to verniers with a reading value of 0.1 mm, verniers with a reading value of 0.05 and 0.02 mm are used.

are intended for precise marking and measuring heights from flat surfaces.

The height gauge (Fig. 4, a) consists of a base 8, in which a rod 1 with a scale is rigidly fixed; frames 2 with vernier 6 and locking screw 3; device for micrometric feed 4, including a slider, a screw, a nut and a locking screw; interchangeable legs for marking 7 with a point and for measuring heights 9 with two measuring surfaces, the bottom flat and the top in the form of a sharp edge no more than 0.2 mm wide (Fig. 4, b); clamp 5 for securing legs 7 and 9 and holder 10 on the protrusion of the frame (Fig. 4, c) for needles of various lengths.

Fig 4.

The scale and vernier are the same as those of other caliper tools.

Measuring or marking with a height gauge is carried out on a marking plate. Before measurement, the zero setting of the instrument is checked. To do this, the frame with the leg is lowered until it comes into contact with the slab or a special base surface (depending on the type of leg). In this position, the zero division of the vernier must coincide with the zero division of the rod scale.

After aligning the height gauge, you can begin measurements. When measuring the height of a part, the frame with the leg is lowered manually, slightly short of the part. Further movement of the leg until it comes into contact with the part is carried out using a micrometric feed nut. The degree of pressing of the leg to the part is determined by touch. In the installed position, the frame is secured.

When marking, the size is set according to the vernier and rod scales in advance. The mark on the part is drawn with the sharp end of the leg when moving the height gauge along the plate. When measuring with needles (Fig. 4, c), it is necessary to subtract the value m from the reading of the height gauge M, which corresponds to the position of frame 2 when the tip of the needle is in the same plane with the plane of the base.

Dial indicators . Due to the small measurement range, instruments of this group are intended mainly for relative (comparative) measurements by determining deviations from a given size. In combination with special devices, these devices can also be used for direct measurements. They are also used to control the correctness of the geometric shapes of machine parts and their relative position. The most widespread of the devices in this group are dial indicators (Fig. 5, a) with a division value of 0.01 mm; Indicators with a division value of 0.002 mm are also used.

When the measuring rod moves 1 mm, the indicator needle makes a full revolution. Indicators whose measurement limits are more than 3 mm have a revolution counter arrow.

Measurement practice. Dial indicators are used when measuring radial and axial runout, deviations from straightness, deviations in the position of one part relative to another, when checking the relative position of surfaces, etc.

Rice. 5. Dial type indicator (a) and installation of the indicator for measurement:b – on a universal tripod; c – various ways to mount the indicator head on a tripod

When taking measurements, use a universal tripod and other devices.

The indicator installed in a universal tripod (Fig. 5, b) can occupy a variety of positions in relation to the product being tested. Design universal tripods may be different, but circuit diagram them remains the same. The options are shown in Fig. 5, c.

For any measurement with an indicator (absolute or relative), it must be set to a certain initial position. To do this, the measuring tip is brought into contact with the surface of the setting measure (or table). The indicator is adjusted so that the arrow makes 1-2 turns. In this way, tension is given to the indicator rod so that during the measurement process the indicator can show both negative and positive deviations from the initial position or setting standard. In this case, the indicator arrow is set against any scale division. Further readings should be made from this arrow reading, as from the initial one. To make readings easier, the initial reading is usually set to zero. The indicator is set to zero by turning the dial using the grooved bezel.

When measuring indicator bore gauge it is pre-adjusted to the size being measured using a micrometer, a block of plane-parallel gauge blocks or a calibrated ring and then set to zero.

The adjusted bore gauge is carefully inserted into the hole being measured and with slight rocking (Fig. 6, a) the deviation of the needle from the zero position is determined. This will be the deviation of the measured size from the one for which it was configured. In cases where the measuring rod of the indicator head cannot touch the surface being measured, they resort to special lever devices connected to the indicator body. The structure of these devices is clear from the figure (Fig. 6, b).

Rice. 6. Indicator bore gauge (a) and lever devices for the indicator (b), used for measurements in hard-to-reach areas places

Micrometers for external measurements (Fig. 7), micrometer bore gauges and micrometer depth gauges are classified as micrometer instruments.

Rice. 7. 1 – heel; 2 – micrometric screw; 3 – lock nut; 4 – bushing; 5 – drum; 6 – ratchet; 7 – bracket

The reading device of micrometer instruments consists of a sleeve 1 (Fig. 8, a) and a drum 2. On the sleeve, on both sides of the longitudinal line, two scales are marked with divisions of 1 mm so that the upper scale is shifted relative to the lower one by 0.5 mm.

At the beveled end of the drum there is a circular scale with 50 divisions. When rotating, the drum moves along the bushing and covers a distance of 0.5 mm in one revolution. Therefore, the drum scale division price is 0.5:50 = 0.01 mm.

When measuring, a whole number of millimeters is counted on the lower scale, half a millimeter on the upper scale of the sleeve, and hundredths of a millimeter on the drum scale. The number of hundredths of a millimeter is counted according to the division of the drum scale, which coincides with the longitudinal mark on the sleeve.

Examples of readings on micrometer scales are shown in Fig. 8.

Rice. 8. a – 11.0 mm; b – 9.36 mm; c – 10.5 mm; g – 9.86 mm

In order to limit the tension force on the part being measured when measuring with a micrometer and ensure the constancy of this force, the micrometer is equipped with a ratchet.

Before reading the micrometer readings, the drum is secured using a special stopper.

In addition to conventional calipers and other instruments with a vernier scale and a dial scale, models of instruments with electronic digital indicators are also used, which display digital readings of the measurement values ​​on the screen.

When operating measuring instruments, it should be remembered that the measuring surfaces of the tips must be clean, and the measured surfaces of the parts must be clean and their temperature should not differ from the temperature of the measuring instruments. It is unacceptable to measure hot parts with precision measuring instruments. Measuring instruments should not be held in your hands for a long time, as this affects the accuracy of measurements. It is not allowed to measure moving parts, because this is dangerous, leads to rapid wear of the measuring surfaces of the instrument and a loss of accuracy of the measurement results.

For short-term and long-term storage The measuring instrument is wiped with a soft rag containing aviation gasoline and lubricated with a thin layer of technical petroleum jelly. The measuring surfaces of the tips are separated from each other, and the stoppers are loosened. For long-term storage, instruments are wrapped in oiled paper.

Before starting measurements, it is recommended to check the zero readings of the measuring instruments. To do this, first adjust the instrument scale readings to the size being measured using measuring tiles (plane-parallel gauge blocks) or using a calibrated ring or roller and thus determine the zero position during measurements.

Probes serve to determine the size of the gaps with an accuracy of 0.01 mm (Fig. 9).

Rice. 9.

Probes are manufactured of 1st and 2nd accuracy classes with plate thicknesses from 0.03 to 1 mm and with intervals of 0.01 mm or more, depending on the set number.

(Fig. 10) are the main means of checking the flatness of the surface of a part using the paint method. The plates are made of cast iron with dimensions ranging from 100x200 to 1000x1500 mm.

There should be no corrosion spots or pits on the surface of the slabs.

Surface plates serve more than just checking flatness. They are widely used as a basis for various control operations using universal measuring instruments (thicknessers, indicator stands, etc.)

Rice. 10.

Steel straight edges . Deviations from flatness and straightness (deviations in the shape of flat surfaces) are controlled using straight edges (Fig. 11). Straight edges are produced in patterns with a double-sided bevel (Fig. 11, a); triangular (Fig. 11, b) and tetrahedral (Fig. 11, c); with a wide working surface (rectangular section (Fig. 11, d) and I-section (Fig. 11, e), “cast iron bridges” (Fig. 11, f).

Rice. 11

Rulers are available in various sizes (LxHxB mm): a – up to 320x40x8; b – up to 320x30; c – up to 320x25; g – up to 1000x60x12; d – up to 4000x160x30.

Straight edges are made in length: pattern rulers – up to 500 mm, “cast iron bridges” – up to 2500 mm and more. Curve rulers are used to check the straightness of the surface of a part “through the light”, and straight edges “cast iron bridges” are used to check the straightness “for paint”, using a feeler gauge or tissue paper.

When checking for transmission (Fig. 12, a), the straight edge is laid with a sharp bevel on the surface to be checked, and the light source is placed behind the ruler and the part. The minimum slit width that can be detected by the eye is 3...5 µm. To control the lumen gap, probes are usually used.

Rice. 12. Scheme for monitoring deviations from flatness using a pattern ruler “in the light”:a – visually; b – with a sample of gaps

Measuring deviations from straightness with straight lines “in the light” requires skill from the performer. To develop the skill of assessing by eye the magnitude of the deviation from straightness by the size of the lumen, a sample of lumens is used (Fig. 12, b), which consists of a pattern ruler 1, a set of four end length measures with a gradation of 1 micron, two identical end length measures (2) and glass plate 3. When measuring between the end measures of length and the edge of the ruler, “gaps” are formed, colored in different colors due to diffraction of visible light and from the size of the gap between the ruler and the end measure of length.

(Level) - a device used to determine the horizontality of a surface.
A spirit level is a bar in which is fixed a transparent glass tube filled with liquid, usually alcohol, with a small gas bubble. The tube with liquid has an arcuate longitudinal section. If the tube with liquid is located horizontally, the gas bubble is located strictly in the middle of the tube.
Typically, a spirit level contains two tubes with liquid for checking horizontal and vertical surfaces.

A tool used to determine the external dimensions of parts. The readings are taken using a measuring ruler with an accuracy of about 0.5 mm.
The caliper consists of two curved, hinged legs.

A device used to measure tortuous curved segments, mainly on topographic maps.
When making measurements, the cogwheel of the curvimeter is rolled along a winding line on the map. The distance traveled is measured using the dial. Typically, a mechanical curvimeter is equipped with two dials, one of which is graduated in centimeters and the other in inches.
The measurement error of a mechanical curvimeter is 0.5%.

Measuring ruler- a tool with which linear dimensions are measured.
The readings of measuring instruments, such as calipers, bore gauges, etc., are taken using a measuring ruler.
The ruler scale has a division value of 1mm or 0.5mm. Every 5mm, the stroke on the ruler is slightly larger. Every 1 cm, an even more elongated stroke is provided with a number indicating the number of centimeters before the beginning of the scale.

Test ruler- a tool used to check the straightness of surfaces.

A tool used to transfer angle dimensions from a part to a goniometer tool or to a workpiece.
In the production of carpentry they use wooden spoon . She represents block with a slot and pen . The feather and the shoe are hinged together using a screw and a wing nut. In order to install the pen in the desired position, you need to loosen and then tighten the knob. In the non-working position, the feather is retracted into the slot of the block, while the small one does not take up much space.
In the production of metalwork marking works they use metal grinder .

A tool with which measurements are made with an accuracy of 0.01mm.
The micrometer contains bracket With heel , micrometer screw in increments of 0.5mm and stopper . The micrometer screw consists of stem , drum , And heads .
Longitudinal scale , applied to the stem, divided by a risk into main And auxiliary so that the distance between the marks of the two scales is 0.5 mm. The circumference of the drum is divided into 50 equal divisions. Rotating the drum by one division moves the micrometer screw by 0.01 mm.
Ratchet , which the head is equipped with, allows you to transmit a constant force to the micrometer screw.
In the case when the micrometer screw rests on the heel, the end of the drum should align with the zero division of the main longitudinal scale. In this case, the zero division of the circular scale on the drum must coincide with the longitudinal mark of the main scale.
In the figure shown, the end of the drum has moved 16 divisions from zero on the main scale and another division on the auxiliary scale. The 37th division of the circular scale of the drum was combined with the longitudinal mark of the main scale. Thus, the size plotted on the micrometer is: 16 + 0.5 + 0.37 = 16.87 mm.

A tool used to determine the internal dimensions of parts. The readings are taken using a measuring ruler with an accuracy of about 0.5 mm.
The bore gauge consists of two legs connected by a hinge. The lower ends of the legs are curved outward.

A device used to check the verticality of structures such as pillars, supports, brickwork etc.
A plumb line consists of a thin thread with a weight attached to its end. The weight is usually given the appearance of a cylinder, sharpened into a cone.

Basic marking device.
All dimensions are measured from the surface of the slab, which are marked by marks on the parts during spatial markings.
Marking plates are made by casting from fine-grained gray cast iron. At the bottom of the slab there are stiffening ribs that prevent it from bending under the weight of the parts being marked and under the weight of the slab itself.
The working plane of the slab is processed on precision planing machines and then scraped. To facilitate the installation of various devices on the stove, the working surface of the plates is sometimes divided into squares by grooves 2 - 3 mm deep and 1 - 2 mm wide.

Testing and marking prisms- devices used to check and mark shafts and cylindrical parts.
Prisms are manufactured in sets in pairs, which allows them to be used as supports when inspecting and marking long cylindrical parts.

A measuring tool consisting of a set of various threaded templates. The thread gauge is used to measure the pitch of a metric thread, or for an inch thread the number of turns per inch.
A thread template is a toothed plate with a specific tooth pitch. Each metric template indicates the thread pitch in millimeters, and each inch template indicates the number of turns per inch of thread.
A set of templates is placed in a frame of two overlays, fastened with screws. The metric thread gauge is marked: “M60°”, and the inch thread gauge is marked “D55°”.

A marking tool used to mark parts spatially.
On basis The thicknesser is secured in the required position using a nut. rack . The tilt of the stand at a slight angle is ensured by a set screw. is installed on the stand and secured in the desired position with a nut.
The thicknesser and the part are placed on the marking plate. Place the stand and scriber in the required position. Move the thicknesser around the part. Using a scriber, marks are made on the part at an equal distance from the surface of the marking plate.

Bench square- a tool used to check and mark right angles.
A square is also convenient for drawing straight parallel lines. A square is used to check the perpendicularity of parts during equipment assembly.
Distinguish flat squares, squares with "heel" , sold out squares.

A square used to find the center of a cylindrical part.
The center finder consists of rulers , fixed on square in such a way that one of the faces of the ruler is the bisector of the right angle of the square.
To determine the center of the circle, place a square on the end of the part so that both of its faces touch the side surfaces of the part. Using a ruler, apply a mark to the part using a ruler. Rotate the square to a certain angle and repeat the operation. The intersection of the two marks is the center of the circle.

A tool with which markings in the form of arcs or circles are applied to the materials being processed. Compasses are also used to transfer dimensions from the ruler to the part.
At a tightly compressed compass ends of legs should converge without gap. The sharply sharpened ends of the legs are hardened. The required distance between the legs of the compass is fixed using arcs And screw .
Before drawing a circle or arc onto the material, it is necessary to mark their center with a center punch.

A tool used to mark marks on the materials being processed.
The scriber is made from tool steel. The edge is hardened. For ease of operation, the middle thickened part of the scriber is rolled. Sometimes, to make marks in hard-to-reach places, one end of the scriber is bent at a right angle.

A tool used to make measurements, the error of which does not exceed 0.1 mm. A caliper allows you to measure external and internal dimensions, as well as depth.
Barbell with millimeter graduations ends on one side depth gauge , and on the other hand motionless lips . To the motionless sponges movable jaws are adjacent .
The movable jaws are equipped with an auxiliary scale called vernier . Using a vernier it is possible to make measurements with an accuracy of 0.1 mm. Movable jaws can move freely along the rod. In the desired position, the movable jaws are fixed using locking screw .
The vernier scale, 19 mm long, is divided into parts, 1.9 mm each. In the case when the zero line of the vernier aligns with one of the scale divisions on the rod, the remaining divisions of the vernier (except for the last tenth) will not coincide with the divisions of the main scale. The first line of the vernier and the second division of the millimeter scale differ by 0.1 mm. The second division of the vernier and the fourth division of the rod are 0.2 mm, the third and sixth are 0.3 mm, the fourth and eighth are 0.4 mm, the fifth is in the middle between the ninth and tenth.

When making measurements, whole millimeters are counted on the main scale on the rod opposite the zero division of the vernier. Tenths of a millimeter are counted according to the division of the vernier, which coincides with the division of the main scale on the rod. The illustration shows examples of sizes 0.1mm, 0.3mm and 88.4mm.
There are designs of calipers capable of making measurements, the error of which does not exceed 0.05mm and 0.02mm.