6.1. Methods and means for measuring holes. Bore gauges. Calipers. Hose depth gauge. Plug gauges.

When working on drilling machines The driller must often use a measuring tool to control the diameters and depths of holes, as well as other dimensions.

The dimensions of the holes are measured and checked using various control and measuring instruments, which are selected depending on the required accuracy of the measured size and the nature of production.

Often a driller has to use the following measuring tools: a measuring ruler, bore gauge, squares, calipers, smooth and threaded gauges, and a depth gauge.

The measuring ruler is a rigid steel tape with a length of 150 to 1000 mm or more with divisions marked on it every 1 mm and is used for approximate measurements overall dimensions workpieces being processed, distances between hole centers, hole diameters, etc. Possible measurement accuracy with a ruler is up to 0.5 mm.

Rice. 6.1. Bore gauges:

a - indicator, b - micrometric

Indicator bore gauge(Fig. 6.1, a) are used to measure precise holes with a diameter of 6 mm or more. The error of the bore gauge readings is from ±0.15 to 0.025 mm. The division value is 0.01 mm. The set of bore gauges includes a set of replaceable inserts, with the help of which the required measurement limits are set.

The indicator is set to zero using a certified ring or gauge block. When measuring the diameter of a hole, the bore gauge, having previously tilted it, is carefully inserted into the hole without hitting the tips on the walls of the workpiece.

The bore gauge is installed perpendicular to the axis of the hole by gently rocking it, after which the deviation of the arrow from zero is noted. If, during measurement, the indicator arrow deviates to the right, the measured size is less than the configured one, if it deviates to the left, it is larger than the configured one.

For example, when measuring a hole with a diameter of 25 mm, the indicator arrow deviated to the right by 15 divisions, therefore, the actual size of the hole will be equal to 25 - 0.15 = 24.85 mm. If the arrow deviates by the same number of divisions to the left, the measured size will be 25 + 0.15 = 25.15 mm.

To check precise holes, micrometric bore gauges are used, which have a division value of 0.01 mm and an indication error of no less than ±0.006 mm.

Micrometric bore gauge(Fig. 6.1, b) has the following main parts: stem 3 with a spherical measuring tip 1 pressed into it, micrometric screw 5, drum 6 rigidly connected to the micrometric screw, cap 7 securing the drum to the micrometric screw, measuring tip 8, safety cap 2 and stopper 4.

Bore gauges They are produced in the form of a micrometer head and several extensions, which can be screwed together to obtain different measurement limits.

Calipers have a special scale - vernier, which allows you to take readings with an accuracy of 0.1 and 0.05 mm.

Rice. 6.2. Calipers:

a - with reading on the vernier, b - readings on the vernier, c - with reading on the indicator

In Fig. 6.2, and shown calipers with a vernier reading accuracy of 0.05 mm. It is intended for external and internal measurements, as well as for marking work. The caliper consists of a rod 6 with millimeter divisions, at one end of which there are two jaws 1 and 2. A frame 9 with jaws 11 and 3 moves along the rod 6. A vernier ruler 10 is mounted on the frame.

To facilitate accurate measurements in individual designs Vernier calipers have a micrometric device for feeding the frame 9, consisting of a screw 8, a nut 7 and a clamping screw 5. The locking screw 4 serves to secure the frame 9 to the rod 6.

Vernier 10 is used to count fractional parts of the bar scale division 6. Its length is 39 mm and it is divided into 20 parts. The numbers indicate the number of hundredths of a millimeter every five divisions. Therefore, against the fifth line of the vernier there is the number 25, against the tenth - 50, etc. The length of each division of the vernier is 39:20 = 1.95 mm, i.e. the reading can be made with an accuracy of 0.05 mm.

When measuring with a caliper to the number of whole millimeters passed by the zero strokes of the vernier, one must add as many hundredths of a millimeter as the vernier stroke will show, coinciding with the strokes of the measuring rod. For example, along the caliper rod (Fig. 6.2, b), the zero stroke of the vernier passed 24 mm, and its eighth stroke coincided with one of the strokes of the measuring rod. In this case, the stroke corresponds to a size of 0.40 mm (0.05X8), and the measured size is 24.40 mm, i.e. 24 + 0.40= 24.40 mm.

Calipers are manufactured with measurement limits from 0 to 125, 160, 250, 400, 630, 1000 mm and more.

When measuring the diameter of the hole, jaws 1 and 11 of the caliper are inserted into the hole and their position is fixed with screw 4. Then, according to the readings of the vernier, the diameter size is determined. In this case, the actual thickness of jaws 1 and 11 for internal measurements is added to the calculated size.

Calipers with reading according to the indicator (Fig. 6.2, c) are used for external and internal measurements, as well as for marking work. An indicator with a division value on the dial of 0.02 mm is mounted on the movable frame of the caliper. One turn of the arrow is equal to 2 mm. Maximum measurement error with large measuring jaws is ±30 µm. When measuring with a caliper, a combined reading of the measured values ​​occurs: a rough indication of the position of the slider on a linear scale, as well as a precise indication of the effective measured value by the position of the arrow on the dial. Measuring range 0-150 mm.

Rice. 6.3 . Methods for measuring hole depth: a - a depth gauge, b - a micrometric depth gauge, c - an indicator depth gauge, d - a limit template-depth gauge

Hose depth gauge(Fig. 6.3, a) are used to measure the depth of holes, recesses, grooves and the size of protrusions. Its design is similar to that of a caliper.

Rod 4, having millimeter divisions, moves freely in frame 8 with vernier 1 and base 9 and is secured in the desired position with locking screw 2. Frame 8 is connected to a micrometer feed mechanism consisting of slider 5, screw 7, nut 6 and locking screw 3.

To measure the depth drilled hole using a depth gauge, you need to press the base 9 to the surface of the part with your left hand, and right hand, rotating nut 6, bring rod 4 into contact with the bottom of the drilled hole.

The vernier reading is carried out in the same way as when measuring with a vernier caliper. Vernier depth gauges are manufactured with upper measurement limits of up to 150, 200, 300 and 500 mm and with an accuracy of 0.1 to 0.02 mm.

Micrometric depth gauge(Fig. 6.3, b) allows you to measure holes with a depth of 0-25; 25—50; 50-75; 75-100 mm with an accuracy of 0.01 mm. With its base 1 it is installed on the machined surface of the part 7 and pressed tightly against it. Then, by rotating the ratchet 3, the measuring rod 6 of the micrometric screw 5 moves until it comes into contact with the bottom of the hole. The distance between the measuring planes of the base and the rod of the micrometer screw determines the depth of the hole, groove, etc. The dimensions are measured on the scale of stem 4 and drum 2.

Indicative depth gauge(Fig. 6.3, b) is a measuring device with a reading device - a dial indicator with gear transmission from the measuring rod to the reference pointer.

The arrow rotates around an axis and gives readings on a circular scale. One revolution of the arrow corresponds to moving the measuring rod by 1 mm, i.e., the indicator division value is 0.01 mm. Whole millimeters are counted on the second scale of the dial with a small hand.

Indicative depth gauge consists of a body 2, a large 3 and a small 5 dial scale, a reading pointer 4 and a measuring rod 6. To measure the depth of a hole, the depth gauge is installed on the surface of the part with its base 1. Templates-depth gauges (Fig. 6.3, d) are recommended to be used to check the depth of holes up to 100 mm. They can quickly and reliably check the depth of machined holes within specified tolerances.

Smooth calibers— scaleless measuring instruments; used primarily in serial or mass production to control the correct production of holes. They provide fast and accurate measurements and are divided into normal and limit.

Normal calibers have dimensions equal only to the nominal size of the product element being tested. These gauges are included in the part being tested with a greater or lesser degree of density.

Currently, maximum calibers are mainly used. They are made double-sided, of which one side has the largest and the other has the smallest maximum dimensions of the part. One side is called passing (PR), and the other is called non-passing (NOT).

Rice. 6.4. Plug gauges: a - smooth limit, b - threaded

To the extreme smooth calibers These include smooth plugs (Fig. 6.4, a), which are used to check holes. For smooth plugs, the passing side is considered to be the side with the smallest maximum size, and the non-passing side is the side with the largest.

If the non-passing sides of the gauges fit into the hole, then the products are considered final defects. If the pass-through sides of the calibers do not fit into the hole, then the products can be corrected.

Products having internal threads, are controlled by thread gauges. Thread gauges for checking internal threads are prototypes of mating products.

The working gauges for monitoring internal threads are threaded plugs: pass-through PR and non-go-through NOT (Fig. 6.4,b).

Screwing the PR plug into the threaded hole shows that the average thread diameter does not exceed the established limit size. If a no-go plug does NOT screw in, it means that the average diameter of the nut is no larger than the specified largest size limit.

Therefore, if a through plug is screwed into a threaded hole, but a non-through plug is not screwed in, the product is considered suitable.

The home craftsman has to constantly deal with measuring length, width and height. An angle of 90° or 45° is also often necessary to maintain. Otherwise, it is impossible to carry out high-quality apartment repairs or make homemade products. Accuracy when performing linear measurements of 1 mm is sufficient in the vast majority of cases, and a tape measure or a simple ruler is suitable for them.

Often, tape measures have an additional bubble level, which allows you to place furniture, a refrigerator and other items horizontally. But the accuracy of this level is not high due to the small length of the tape measure’s supporting plane. In addition, the cone with an air bubble in tape measures is often not installed accurately, which does not ensure horizontalness and the work performed.

On sale, for measurement linear dimensions a wide range of laser measuring instruments, but, unfortunately, due to the high price, they are not available to non-professionals.

Instructions
on the use of calipers (Columbus)

Calipers– this is linear measuring tool serving for measuring external and internal dimensions details including depth, with an accuracy of 0.1 mm.

The design and principle of operation of a vernier caliper

The classic caliper is designed as follows. A movable frame is installed on the measuring rod using grooves. In order for the frame to fit tightly, a flat spring is installed inside and a screw is provided to firmly fix it. Fixation is necessary when carrying out marking work.

The bar is marked with a metric scale in 1 mm increments and numbers indicate centimeter divisions. The frame has an additional scale with 10 divisions, but with a pitch of 1.9 mm. The scale on the frame is called vernier in honor of its inventor, the Portuguese mathematician P. Nunes. The rod and frame have measuring jaws for external and internal measurements. A depth gauge ruler is additionally attached to the frame.

Measurements are taken using a clamp between the jaws of the part. After clamping, the frame is fixed with a screw so that it does not move. The number of millimeters is counted on the scale on the rod to the first vernier mark. Tenths of millimeters are counted from the vernier. Which stroke from left to right on the vernier coincides with any of the scale marks on the rod will be tenths of a millimeter.

As can be seen in the photo, the measured size is 3.5 mm, since from the zero mark of the scale on the rod to the first mark of the vernier there were 3 full divisions (3 mm) and on the vernier the fifth mark of the vernier mark coincided with the scale mark of the rod (one division on the vernier corresponds to 0.1 mm measurements).

Examples of caliper measurements

To measure the thickness or diameter of a part, you need to spread the jaws of the caliper, insert the part into them and bring the jaws together until they touch the surface of the part. It is necessary to ensure that the planes of the jaws when closing are parallel to the plane of the part being measured. The outer diameter of the pipe is measured in exactly the same way as the size of a flat part, only you need to ensure that the jaws touch diametrically opposite sides pipes.

In order to measure the internal dimension in a part or the internal diameter of a pipe, the caliper has additional jaws for internal measurements. They are inserted into the hole and pushed apart until they touch the walls of the part. When measuring the internal diameters of holes, the maximum reading is achieved, and when measuring parallel sides in a hole, the minimum reading is achieved.

In some types of calipers, the jaws do not close to zero and have their own thickness, which is usually stamped on them, for example, the number “10”, although the first mark of the vernier is at the zero mark. When measuring internal holes with such a caliper, 10 mm is added to the readings on the vernier scale.

Using a Columbus-type caliper with a movable depth gauge ruler, you can measure the depth of holes in parts.

To do this, you need to completely extend the depth gauge ruler from the rod and insert it all the way into the hole. Bring the end of the caliper rod all the way into the surface of the part, while not allowing the depth gauge ruler to come out of the hole.

In the photograph, for clarity, I demonstrated the measurement of the depth of the hole by attaching the ruler of the depth gauge of a caliper with outside piece of pipe.

Examples of marking parts with calipers

The caliper is not intended for applying marking lines on materials and details. But if the jaws of a caliper for external measurements are sharpened with fine-grained emery wheel, giving them a sharp shape, as shown in the photo, then marking with a caliper will be quite convenient.

You need to remove excess metal from the jaws very carefully and slowly, avoiding discoloration of the metal of the jaws from strong heating, otherwise you can ruin them. To speed up the work, to cool the sponges, you can periodically dip them for a short time in a container of cold water.

To measure a strip sheet material with parallel sides, you need to move the jaws of the caliper, focusing on the scale to a given size, guide one jaw along the end of the sheet, and scratch a line with the other. Since the caliper jaws are hardened, they do not wear out. You can mark both soft and hard materials (copper, brass, steel). Clearly visible risks remain.

Using sharply sharpened caliper jaws, you can easily mark a circle line. To do this, a shallow hole with a diameter of about 1 mm is made in the center, one of the jaws rests against it, and a circle line is drawn with the other.

Thanks to the refinement of the shape of the caliper jaws for external measurements, it became possible to accurately, conveniently and quickly mark parts for their subsequent machining.

How to measure with a micrometer in practice

You can obtain the size of products with an accuracy of 0.01 mm by taking measurements with a micrometer. There are many modifications, but the most common is a smooth micrometer of the MK-25 type, which provides a measurement range from 0 to 25 mm with an accuracy of 0.01 mm. It is convenient to use a micrometer to measure the diameter of the drill, the thickness of the sheet material, and the diameter of the wire.

The micrometer is a bracket, on one side of which there is a support heel, and on the other there is a stem and a high-precision thread into which a microscrew is screwed. The stem has a metric scale on which millimeters are counted. The microscrew has a second scale with 50 divisions, on which hundredths of mm are measured. The sum of these two quantities is the measured size.

In order to take a measurement with a micrometer, the part is placed between the heel and the end of the micrometer screw and rotated clockwise by the ratchet handle (located at the end of the micrometer screw drum) until the ratchet makes three clicks.

There are two scales on the stem with a step of 1 mm - the main one, digitized every 5 mm, and an additional one, shifted relative to the main one by 0.5 mm. The presence of two scales allows you to increase the precision of measurements.

The readings are taken as follows. First, they read how many whole millimeters, not covered by the drum, are obtained according to the digitized lower scale on the stem. Next, check on the upper scale for the presence of risks located to the right of the lower scale. If the risks are not visible, then proceed to taking readings from the scale on the drum. If the mark is visible, then another 0.5 mm is added to the whole number of millimeters obtained. The readings on the drum are measured relative to a straight line drawn along the stem between the scales.

For example, the size of the measured part is: 13 mm on the lower scale, there is an open mark on the upper scale, there is no mark to the right of the open mark on the lower scale, which means there is no need to add 0.5 mm, plus 0.23 mm on the drum scale, as a result of addition we get: 13 mm+0 mm+0.23 mm=13.23 mm.

A micrometer with a digital readout of measurement results is more convenient to use and allows measurements with an accuracy of up to 0.001 mm.

If, for example, the battery runs out, then with a digital micrometer you can take measurements in exactly the same way as with a smooth MK-25, since there is also a division reading system with an accuracy of 0.01 mm. The price of micrometers with digital readout of measurement results is high and for home handyman unbearable.

How to measure a large diameter pipe

The caliper jaws, with a measuring range from 0 to 125 mm, are 40 mm long and therefore allow you to measure pipes with an outer diameter of up to 80 mm. If necessary, measure the pipe larger diameter or if you don’t have a caliper at hand, you can use the folk way. Wrap the pipe around the circumference with one turn of non-stretch thread or wire, measure the length of this turn using a simple ruler, and then divide the result by the number Π = 3.14. The photo shows a plastic ruler in the form of a triangle with angles of 45º and 90º, with built-in protractor. Using it, you can mark and check the accuracy of the resulting angle.

When performing markup metal parts use a metalworker's square, providing higher measurement accuracy.

How to use a miter box

To obtain a right or 45º angle without marking, it is convenient to use a device called a miter box. Using a miter box, it is convenient to cut trims for doors, moldings, baseboards and much more to size at an angle. The cut is obtained with the required angle automatically.

It is enough to measure the length, place a strip of material between the vertical walls of the miter box and, holding it with your hand, make a cut. To obtain a high-quality end of the board, use a saw with fine teeth. A hacksaw works well for metal. It is possible to saw even varnished boards without chipping the varnish.

An angle of 45 0 when sawing using a miter box is obtained as easily as a straight one. Thanks to the high guide walls of the miter box, you can saw boards of different thicknesses.

You can buy a miter box ready-made, but it is not difficult to make it yourself from available material. It is enough to take three boards of wood or plywood of a suitable size, and screw the other two to the side ends of one of them with self-tapping screws. Make guide cuts at the required angles and the miter box device is ready.

The wide variety of measurement objects leads to a wide variety of control and measuring instruments and instruments, as well as measurement methods and techniques. However, depending on the purpose individual parts machines, measurements must be made with varying accuracy. In one case, it is enough to use a regular scale ruler, and in the other, use a precise instrument that makes it possible to make measurements with an accuracy of ±0.01 mm.

Let's say you want to measure the diameter of a piston. It can be measured with calipers and a scale ruler, calipers and micrometer. In the first case, the measurement accuracy corresponds to -0.5 mm, in the second - from 0.1 to 0.05 mm, and in the third - 0.01 mm.

Normal conditions for performing linear and angular measurements are established by GOST 8.050-73. Errors allowed when measuring linear dimensions from 1 to 500 mm, depending on tolerances and nominal dimensions of products, are regulated in GOST 8.051-73. The limit of permissible measurement error takes into account the influence of the error of measuring instruments, installation standards, temperature deformations, measurement method, etc. The measurement result with an error not exceeding the permissible one is accepted as the actual value.

The main factors influencing the choice of a measuring instrument are the size and quality (accuracy class) of the product being measured, the permissible error of the measuring instrument, the conditions and method of using the measuring instrument.

Sliding measuring tool with linear vernier. Vernier calipers are a multi-dimensional sliding tool with a vernier * for measuring external and internal dimensions, diameters, depths and heights of parts. The designs of manufactured calipers allow measuring dimensions with an accuracy of 0.1 and 0.05 mm. Such high accuracy is achieved by using a special device for counting - a linear vernier.

In Fig. 129 shows a caliper (universal) with measurement accuracy up to 0.1 mm GOST 116-89. It consists of a rod 1, on which a ruler scale is printed, jaws 2 and 9, and a frame 7 moving along the rod with frame jaws 3 and 8.

Rice. 129

The object being measured is lightly clamped between the jaws, the frame is fixed with clamping screw 4, and then the size is measured using the rod and vernier scales. In the groove on the back side of the rod, ruler 5 of the depth gauge, which is a flat rod, slides freely. One end of it is rigidly connected to the frame. In the closed position, the free end of the depth gauge ruler exactly coincides with the end of the rod. When measuring depth, the end of the rod is installed on the plane of the part near the hole being measured. By pressing on the frame, the depth gauge rod is moved all the way to the bottom of the hole and then the position of the frame is fixed with a clamping screw.

Dimensions are measured using the rod and vernier. The 19 mm long vernier is divided into 10 parts. One of its divisions is thus 19/10 = 1.9 mm, which is 0.1 mm less than a whole millimeter (Fig. 130, I). With a zero reading, the vernier stroke is located from the bar stroke closest to the right at a distance equal to the reading value of 0.1 mm, multiplied by the serial number of the vernier stroke, not counting the zero one (Fig. 130, II). An integer number of millimeters is counted on the rod scale from left to right by the zero stroke of the vernier. The fractional value (the number of tenths of a millimeter) is determined by multiplying the reading value OD mm by the serial number of the vernier stroke (not counting zero), coinciding with the bar stroke.

In Fig. 130, III shows two examples of readings. In the first, on the rod scale we read the integer 39 mm, then on the vernier scale we determine the fractional value 0.1 mm x 7 = 0.7 mm (the seventh line is indicated by a cross). This means that the measured size is 39 mm + 0.7 mm = 39.7 mm. In the second example, similarly to the first, we define 61 mm + 0.1 mm x 4 = 61.4 mm.

Rice. 130

A reading accuracy of 0.1 mm is sometimes insufficient. In this case, use a caliper that allows you to measure with an accuracy of 0.05 mm.

Vernier depth gauge(GOST 162-90) (Fig. 131) is intended for measuring the depth of blind holes, grooves, grooves, ledges and heights with a vernier reading value of 0.1 and 0.05 mm. It differs from a caliper only in design: the rod ends with a cut end, which is the measuring surface; instead of jaws, the frame has a wide supporting surface - base 1.

Rice. 131

When taking measurements, the depth gauge is installed with its base above the hole, and the rod is extended until it stops at its bottom. Further, all actions are similar to the operation of measuring the part with a caliper.

Micrometric measuring instrument. Micrometer(GOST 6507-90) - a more complex tool in design than those discussed earlier (Fig. 132). It allows measurements to be made with greater accuracy.

Rice. 132

A micrometer for external measurements consists of a horseshoe-shaped bracket 1, a heel 2, a stem 5, a clamping device - stopper 4, a drum 6 with a micrometer screw 3, a cap 7 with a notch screwed onto the right side of the drum, and a ratchet attached with a screw to the end of the neck cap. Measurement readings are made using a scale on the stem 5 and a scale on the conical vernier of the drum 6.

The scale on the stem has 25 divisions, marked along the axis of the stem at the top and bottom and perpendicular to it with a distance of 1 mm between them. The strokes located above the mark are shifted to the right relative to the lower strokes by 0.5 mm. An integer number of millimeters is counted along the lower strokes, and 0.5 mm along the upper strokes. Hundredths of a millimeter are determined using divisions on the vernier, the surface of which is divided by strokes in the form of generatrices of the vernier into 50 equal parts.

When turned by one division, the micrometer screw 3 connected to the drum 6 moves along the axis by 1/50 of a step, i.e., a distance equal to 0.5 mm: 50 = 0.01 mm.

To determine any size of a part with a micrometer, it is placed between the heel 2 and the end of the micrometer screw 3. Then the drum is turned until the end of the micrometer screw approaches the surface of the part. Further advancement of screw 3 is carried out using cap 7 with a ratchet. Having heard a characteristic crack, similar to the crack of a watch spring during winding, stop turning the cap. After this, stopper 4 is used to lock the micrometer screw, separate the micrometer from the part and read the readings.

The readings are taken as follows (Fig. 133): if the edge of the drum stops closer to the bottom line of the stem (Fig. 133, I), then the number of whole millimeters of the resulting size is determined by the lower division of the scale, and the number of hundredths of a millimeter is determined by the readings of the drum. Thus, the position of the scales shown in the figure corresponds to size 8 + 0.24 = 8.24 mm;

Rice. 133

if the edge of the drum stops closer to the top stroke of the stem, then the resulting size will represent the sum of three values: the number of whole millimeters to the division on the stem closest to the edge of the drum plus 0.5 mm from it to the upper division and plus the reading of hundredths of a millimeter along the drum. In the above case (Fig. 133, II), the position of the scales corresponds to size 8 + 0.5 + 0.24 = 8.74 mm. In Fig. 134 shows techniques for measuring parts with a micrometer.

Rice. 134

Micrometric bore gauge (shtikhmas)(GOST 10-88) is used to measure the internal dimensions of parts, as well as the dimensions of hole diameters. The accuracy of measurements with a bore gauge is the same as with a micrometer - 0.01 mm. It consists (Fig. 135) of a head and replaceable gauge rods (extensions). The micrometer head consists of a micrometer screw 6 located inside the drum 4, a cap 5, a stem 3, a locking device 2 and a replaceable tip 1. Using replaceable tips (extensions), the measurement limit is increased.

Rice. 135

Read the dimensions when using this tool in the same way as when taking measurements with a micrometer.

Tool for measuring angles and tapers. Angle dimensions, like all others, may have tolerances. Upper and lower deviations angular dimensions placed on the drawings in the same way. as well as linear dimensions. For example, means an angle with a nominal size of 90°, the upper tolerance which is 10°, and the lower one is 8°. When corner dimensions on drawings do not have tolerances, they are set according to industry standards.

Various tools are used to measure angles and cones. Let's look at some of them.

Universal protractor(GOST 5378-88) (Fig. 136) are used to measure external and internal corners various parts.

Rice. 10

The goniometer consists of a base 1, on which the main scale is applied on an arc of 130°, and a ruler 4 rigidly attached to it. Sector 3, carrying a vernier 2, moves along the arc of the base. A square 6 can be attached to sector 3 by means of a holder 7, in which in turn, with the help of holder 8, a removable ruler 5 is fixed. The square 6 and the removable ruler 5 have the ability to move along the edge of sector 3.

Although the main scale of the protractor is marked only on an arc of 130°, by changing the installation of the measuring parts, it is possible to measure angles from 0 to 320°. The accuracy of the reading on the vernier is 2". The reading obtained during the measurement angular values or when setting a given angle, it is done in the same way as on the linear scales of a vernier tool, i.e., according to the scale and vernier. The number of degrees is counted on the base scale, and minutes - on the ionius scale.

For example, in Fig. 137, the zero stroke of the vernier falls on the division between 76 and 77° of the main scale, and the 9th stroke of the vernier coincides with the stroke (marked with a cross) of the base scale. Therefore, the main scale reads 76°, and the vernier scale reads 9 x 2" = 18". This means that the angle in this case is 76°18".

Rice. 137

Calibers and templates. Limit calibers - staples GOST 16775-71...16777-71 is used to control the outer diameters of shafts according to the maximum dimensions.

The limit bracket has two sides with dimensions: the largest permissible PR - the passing side and the smallest permissible NOT - the non-passing side.

In Fig. 138 shows a diagram and method of monitoring the measured shaft diameter with 1 pass-through bracket; 2 - no-go bracket; 3 - pass-through bracket. The difference between these dimensions is the tolerance on the diameter of the controlled shaft. The side of the shackle is NOT made to the smallest diameter allowed so that the shaft does not pass through it. The actual size of the shaft diameter cannot be determined with this type of control. It is also impossible to establish the actual size of deviations from the geometric shapes of the shaft, i.e. ovality, taper, etc. To determine the actual size of the shaft diameter and the actual deviations expressed in numerical values, universal measuring instruments should be used.

Rice. 138

Limit calibers - plugs(Fig. 139) are used to control cylindrical holes according to GOST 24962-81, to determine whether the size of the hole diameter corresponds to the limit (tolerance) specified in the drawing. The principle of control with this caliber is similar to the previous one.

Rice. 139

To check cylindrical fastening threads II, working, receiving and control gauges GOST 24963-81 are used. Working gauges are used to check the correct dimensions of the threads of products during their manufacturing process. Receiving gauges - for checking the correctness of thread sizes by inspectors and customers. Control gauges (counter gauges) - for monitoring and adjusting (setting) the sizes of working gauges.

Templates are widely used in mechanical engineering for testing parts with complex profiles. The profile of the template (hence the name profile gauge - template) in theory represents the ideal shape that should be given to the part. Checking with a template involves applying it to the product and assessing the size of the light gap between the profile being checked and the measuring edge of the template. Templates control the tooth profile gear wheels I and the teeth of the running threads II, the profile of the cams and keyways, rounding radii, sharpening angles of cutting tools, etc. (Fig. 140).

Rice. 140

Profile templates are used to determine deviations of the actual tooth profile from the theoretical one. The check consists of placing a template on the wheel tooth and determining the deviation by the size of the light gap in the clearance. This check does not give numerical expression deviations, but in many cases it is sufficient.

In addition to special templates for individual purposes, normalized templates are also used in production. One of them, GOST 4126-82, is shown in Fig. 141. It is a set of steel plates with ends rounded to a certain radius (marked on the plates). This radius meter has a set of plates for measuring radii from 1 to 6.5 mm. The industry has radius meters of larger sizes.

Rice. 141

Measuring cylindrical threads. The most popular means of measuring and monitoring threads are thread micrometers and thread gauges.

Thread micrometer GOST 4380-86 is intended for measuring the average diameter of the external thread on a rod (Fig. 142,I). Externally, it differs from the usual one only in the presence of measuring inserts: a conical tip inserted into the microscrew hole and a prismatic tip placed into the heel hole. Inserts for the micrometer are made in pairs, each of which is designed to measure fastening threads with a profile angle of 55 or 60° with a certain pitch. For example, one pair of inserts is used in cases where it is necessary to measure threads in increments of 1 ... 1.75 mm, the other - 1.75 ... 2.5 mm, etc.

Rice. 142

After setting the micrometer to zero, the inserts seem to hug one turn of the thread being tested (Fig. 142, II). After the inserts have come into contact with the thread surface, lock the micrometer screw and read the result on the scales of the micrometer head (Fig. 142, III).

Thread gauges GOST 519-77 (Fig. 143) is used to measure thread pitch. These are sets of templates (thin steel plates), the measuring part of which is a profile of a standard thread of a certain pitch or number of threads per inch to calculate the pitch. Thread gauges are made of two types: on one of them No. 1 the stamp “M60°” is stamped, on the other No. 2 - “D55°”.

Rice. 143

To measure the thread pitch, select a plate template (comb), the teeth of which coincide with the cavities of the thread being measured. Then read the pitch or number of threads per inch indicated on the plate. To determine the pitch using thread gauge No. 2, an inch is required - 25.4 mm divided by the number of threads indicated on the template.

Outer thread diameter<2 на стержне или внутренний диа­метр резьбы D 1 в отверстии из­меряют штангенциркулем. Зная два этих исходных параметра, подбирают точное значение резь­бы по сравнительным таблицам стандартных резьб.

Measuring gear elements. In the drawing of gears, the size of the tooth thickness (chord length) is always specified as a calculated value.

Vernier gauge- a tool for measuring the tooth thickness of gears (Fig. 144). It consists of two mutually perpendicular rulers 1 and 5 with scales. Ruler 1 is used to set a given height, and ruler 5 is used to measure the thickness of the tooth - the length of the chord along this height. Note that the thickness of the tooth, measured along the chord of the pitch circle, is always at a certain distance from the circle of the tops of the teeth, which is specially indicated in the drawing.

Rice. 144

At the beginning of the measurement, stop 3 is set using vernier 2 to the size of the given height and fixed with a locking screw. The vernier gauge with stop 3 is placed on the circumference of the top of the tooth that is going to be measured. Then the jaws of the horizontal ruler are moved until they come into contact with the tooth profile, after which the size of the tooth thickness is measured using a vernier scale 4, just as when measuring with a caliper.

Usually, when they talk about measurement accuracy, they mean the maximum deviation from the true size that can be obtained during measurement. For example, a measurement accuracy of ±0.02 indicates that the true value may differ from what is read on the instrument scale by a maximum of 0.02 mm. This value characterizes the measuring instrument, but for practice it is inconvenient, since it does not directly indicate when, in the current circumstances, and with what instrument the measurement should be made. In this case, it is more convenient to associate the tool type with the tolerance size. The tolerance is always indicated on the drawing. In the absence of a drawing, the tolerance value is chosen depending on the nature of the pairing of this part with others.

Table 15

Measuring tool for external measurement

Rice. 144 A

Table 16

Measuring tool for internal measurements

Rice. 144 B

Table 17

Measuring tool for measuring depth

Rice. 144 V

In table 15, 16 and 17 (Fig. 144 A, B and C) provide recommendations for the use of a measuring tool with scales depending on the established tolerances and dimensions of the part. It gives the upper limits of the tool's use, i.e., the smallest tolerances that can be measured by a given tool. Each of the tool types listed in the table can be used for rougher measurements.

Improvement of methods and means of technical control is carried out through mechanization and automation of control operations and the use of so-called active control, which allows checking the dimensions of parts during their processing. Progressive control means are selected based on the economic efficiency of their use. To mechanize control operations, multidimensional control devices and various mechanical devices are used.

Such multidimensional instruments and devices use various rigid gauges, indicators and devices based on pneumatic, electric contact and other measurement methods.

The industry also has machines with mechanical measuring devices and with electrical contact sensors, the electrical measuring devices of which make it possible to check various geometric and physical parameters of parts with high accuracy.

Devices for automatic control of parts during their processing are most often used when grinding shafts, holes, planes, etc. These devices, installed on machines, give a signal when the part reaches a given size or automatically change the processing mode and stop the machine.

* Vernier - an auxiliary reading device that increases the accuracy of estimating the fractions of divisions of the main scale of a measuring instrument

Installation and troubleshooting of the plumbing system can only be done when the parameters of the pipes are known. It happens that they are difficult to reach, but measurements need to be taken. How to measure in this case? For these purposes, various tools are used: calipers, tape measures, sensors, etc. Using them is not so difficult, but measurements must be taken correctly.

Outer and inner diameter

Most often, this design parameter is measured in inches, which are easily converted into centimeters (the value is multiplied by 2.54). First of all, you need to decide what needs to be measured: the inner diameter of the pipe or the outer diameter. Products used for water and gas supply are usually measured by internal diameter. This is due to the fact that this indicator defines constructs.

The outer diameter can have different values ​​depending on the wall thickness (the mechanical strength of the entire product depends on it). According to GOST 355-52, each subsequent pipe diameter differs from the previous one in better throughput (by 50%). The permeability of a structure is often called the conditional (nominal) diameter. In this case, the indicator usually differs from the internal diameter (by 1-10 mm). This important parameter is considered the main characteristic of the product, which is taken into account during the design and installation process.

We measure with a caliper

Using this high-precision instrument, parameters of various structures are measured. How to measure the diameter of a pipe with a caliper? To do this, you need to spread its jaws, insert the product into them and bring them together so that they are pressed against the surface. When closing, the jaws must be parallel to the cross-sectional plane of the pipe, otherwise the measurement will be incorrect. The internal diameter is also measured with a caliper. On its reverse side there are jaws that are placed inside the structure and moved apart until they abut the walls.

Sometimes it is necessary to measure the diameter of an installed pipe that is too large. In this case, you can measure the chord with a tool and calculate the diameter mathematically. We spread its lips to the maximum distance and apply it to the pipe. The resulting indicator is the length of the chord. To calculate, you will also need to measure the height of the device’s jaws. The diameter is calculated using the formula:

If the jaws are too long, then you can place some part (a block, etc.). Then the height will be calculated using the formula:

We measure with a ruler and tape measure

If the cross section is visible on the pipe, then the diameter can be measured with a regular ruler. We apply it to the cut area so that the scale runs exactly in the center. We take the distance between the required points (for the internal or external diameter). The distance between the extreme points will be the outer diameter. If you need an internal size, you can find out the wall thickness and subtract it from the resulting figure.

Everything is clear with a ruler, but how to measure the diameter of a pipe with a tape measure? This tool is suitable for solid and large structures that are difficult to reach. We wrap the product so that the tape with the scale fits tightly, and find the place where it intersects. The resulting figure is To get the diameter, divide it by (3.14).

Copy method

If you don’t have any tools at hand, but have a camera, then you can use the copying method. How to correctly measure the diameter of a pipe? For this:
- take an object with known dimensions (for example, a brick);

We lay it on the pipe, along its length or next to the cut;
- photograph this area so that you can evaluate the difference in size;
- carry out calculations based on photographs;
- based on the data obtained, we estimate the actual dimensions (it is important to take into account the scale).

We measure with a micrometer

High-precision measurements (up to 0.01) of the pipe can be made using a micrometer. It should be noted that they are convenient for measuring small items. The tool is a bracket equipped with a support heel and a stem with a high-precision thread (for screwing in a microscrew). On the stem you can see a scale with millimeters and their hundredths. This equipment allows you to obtain more accurate indicators.

How to measure the diameter of a pipe with a micrometer? We place the structure between the end of the screw and the heel. We begin to rotate the ratchet handle until it clicks three times. First, we look at the lower scale of the stem, showing the number of whole millimeters. We check for the presence of the risk, which is on the right. If it is not visible, we take readings from the drum. If there is a risk, add 0.5 mm to the resulting number. Measurements on the drum are determined relative to the line on the stem between the scales.

Laser sensors

Modern laser sensors have been created to take dimensions from pipes (and not only). Their advantages: lack of contact with the surface, the ability to use on different structures (hot, sticky), durability and speed of obtaining results. How to measure the diameter of a pipe with such sensors? There are several measurement methods.

With laser triangulation, the beam from the sensor creates a spot on the surface of the structure. Behind the laser is a camera scanner that sees it from different angles. Using these indicators, the digital processor calculates the distance between the sensor and the product.

We measure the diameter using the shading method. In this case, the sensor serves as an emitter and a receiver, but they are located in different housings. Inside it, the laser beam is reflected from a rotating mirror, bends around the measurement area and creates a virtual strip of light. Inside the device, a moving beam passes through a special diode, which measures the duration of shading (corresponds to the size of the object).

Another option is the principle of light section. The sensor is equipped with a laser, camera and electronic circuitry. The laser creates a line perpendicular to the product, and the camera is positioned at a certain angle to it. Any curvature causes the laser line to deform, which is what pushes the sensors away when calculating dimensions.

It was described above how to measure the diameter of a pipe. But it is important to know that some structures have curvature (maximum 1.5 mm per 1 m of length). In this case we talk about their ovality. This parameter is determined by the formula: the difference between the large and small diameters is divided by the nominal one. Allowable ovality: no more than 1% for pipes with a wall up to 20 mm, no more than 0.8% - with a wall more than 20 mm. This parameter is very important because it affects the performance characteristics of the structure.

The occurrence of problems in the water, gas or sewer system often involves pipe installation - replacing a fragment of an old pipe or installing a new one. When performing such work, you will need the skills to determine the diameter of the pipes of your system using improvised means. When installing a new water supply system, it is also necessary to accurately determine the dimensions of old pipes in order to determine the choice of new plastic or metal-plastic pipes.

Of course, there are special tools for carrying out such measurements, for example, a laser meter, a ruler-circometer and others. But what if you are not a professional specialist, and your home tool kit does not include such high-precision instruments? How to measure the diameter of a pipe in another way?

Before answering this question, it is useful to know in what units these indicators are measured. Pipe diameter is usually measured in inches. One inch is equal to 2.54 centimeters.

When working with a pipe, both its internal and external diameter will be measured. The external diameter of the pipe is important due to the fact that it is its value that is taken into account when applying threads and creating threaded connections. The outer diameter is directly dependent on the thickness of the pipe walls. The wall thickness size is the difference between the outer and inner diameters of the pipe.

From words to deeds

There are several ways to measure pipe diameters, differing in their characteristics depending on the conditions that are important to consider in order to avoid mistakes. The choice of a specific measurement method often depends on accessibility to the measurement object. Let's look at some of them.

Most often, the well-known caliper is used to measure the diameter of a pipe. But you may not have it, or if you do have it, it may not be possible to measure a large pipe diameter with it. In this case, the simplest set of tools and knowledge is used:

• flexible ruler (similar to the type of measuring tape used in sewing);
• roulette;
• school knowledge of the number Pi (it is equal to 3.14).

Using a similar set of tools, you can measure the diameter of not only a pipe, but also any other round object - a rod, column or garden bed.

We only need to make one measurement - determine the circumference of the pipe using a tape measure or flexible ruler. To do this, a measuring tape or tape measure is placed on the surface of the pipe in its widest part. The resulting circumference value should be divided by 3.14. For more accurate dimensions, use the value - 3.1416.

It should be noted that imported supplies of pipes are accompanied by documentation that already indicates the pipe diameters in inches. To convert these values ​​to centimeters, they are multiplied by 2.54. Similarly, to convert centimeters back to inches, multiply by 0.398.

Measurements are taken using a caliper without any mathematical calculations. The condition is complete accessibility to the pipe. This method is suitable for measuring accessible pipes of small diameter (no more than 15 cm). To take measurements, the legs of the caliper are applied to the end of the pipe and clamped tightly on the outer walls. The resulting value on the caliper scale, accurate to tenths of a millimeter, will be the outer diameter of the pipe.

If the end part of the pipe is inaccessible for measurement, that is, when the pipe is a mounted element of an already existing water or gas supply circuit, then for measurements a caliper is applied to the side surface of the pipe. In this case, an important condition for taking measurements is that the length of the caliper legs must exceed half the diameter of the pipe.

Large diameter pipe measurement

We have already mentioned a formula with a value above. The circumference of a large pipe can be measured using a cord or tape measure, and then its diameter is determined using the formula D = L: 3.14, where: D is the diameter of the pipe;

L – pipe circumference.

For example, if the length of the pipe circumference you measured was 31.4 cm, then the pipe diameter will be D = 31.4:3.14 = 10 cm (or 100 mm).

Measuring pipes using photography (copy method)

This non-standard method is used when there is complete inaccessibility to a pipe of any size. A ruler or any other object is applied to the pipe being measured, the dimensions of which are known in advance to any master (often in this case they use a matchbox, the length of which is 5 cm, or a coin). Next, this section of the pipe with the attached object is photographed (in addition to a camera, in modern conditions it is also possible to use a mobile phone). The following size calculations are made from photographs: the visual thickness in mm is measured in the photograph, and then converted into real values, taking into account the scale of the photographs.

Determining the internal diameter of an accessible pipe

Using a regular ruler or caliper, measure the thickness of the pipe wall at its cut. This value, multiplied by 2, is subtracted from the outer diameter values. The resulting value will be equal to the internal diameter of the pipe.

Monitoring pipe parameters in production conditions

The outer diameter of water or sewer pipes in large production conditions is controlled and checked using a more complicated formula: D = L: 3.14 - 2∆p - 0.2 mm.

In this formula, in addition to the already known values, the symbols ∆p mean the thickness of the tape measure in mm, which you use to measure the diameter, and “0.2 mm” from the formula are the permissible deviations that take into account the fit of the tape measure to the pipe. The permissible deviation value for pipes with a cross-section of 200 mm is ±1.5 mm.

When measuring large diameter pipes, permissible deviations are measured as percentages. Example, for products ranging in size from 820 to 1020 mm, permissible deviation = 0.7%. For such measurements, an ultrasound-based measuring system is used.

In large production conditions, the wall thickness of pipes is measured with a caliper with a scale division of 0.01 mm. The permissible deviation from the nominal thickness towards reduction should not exceed 5%.

The values ​​of pipe curvature are also subject to control, which should not be higher than 1.5 mm per linear meter of pipe length. The total curvature of products in relation to its length should not be more than 0.15%. The ovality of the pipe ends is determined by the ratio of the difference between the largest and smallest diameters to the nominal diameter of the pipe.

The value of this parameter should not exceed 1% for pipes with a wall thickness of up to 20 mm and not higher than 0.8% for walls above 20 mm.

The ovality of the pipe can be determined by measuring the diameter of the pipe end using an indicator clamp or bore gauge in two mutually perpendicular planes.

Simple school knowledge and careful use of simple tools will significantly simplify your task - how to measure the diameter of a pipe using improvised means.

Video

We suggest watching a video about working with measuring instruments.