The reliability of measuring instruments depends on the accuracy of their manufacture and the fit of the main parts. As the tool wears out, it must be repaired by eliminating the curvature of the rod guide ribs, non-parallel or non-perpendicularity of the working surfaces of the jaws, frame distortion, etc.
The working surface of the rods of lifting tools is checked by the paint on the surface plate; irregularities are filed off with a personal file and finished on a lapping cast-iron plate. In this case, it is necessary to maintain the parallelism of the ribs within 0.02-0.03 mm. The measuring jaws of the front part of the booms and the base of the height gauges must be machined at an angle of 90°.
ron. Then the rivets are driven into the holes and riveted flush with the surface of the cheeks. Having secured the jaws to the rod 3 and frame 9 and made sure that they are firmly installed in the grooves, file and clean them along the entire contour, while using a test square to check the perpendicularity of their working surfaces to the surface of the edge of the rod. Having filed and cleaned all the outer surfaces, as well as the working surfaces of the jaws, they are thermally treated to a hardness of HRC 56-58 and tempered by 2-3 units. After this, the outer surfaces of the frame and jaws are thoroughly cleaned, the vernier 4 is installed and secured with screws in the frame, springs are inserted into the clamp and frame and put on the rod 3. The assembled caliper is secured in a metalworking vice and they begin to fine-tune the measuring planes of the jaws.
When fine-tuning the measuring planes of the jaws 6 and 7 (Fig. 145) of the caliper, you should use a square to check their perpendicularity to the plane of the rod 3. The parallelism of the ribs of the rod and the planes of the jaws is checked using end gauges clamped
screws between the measuring planes when moving the frame every 10 mm of the rod length.
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When moving frames with jaws along rod 3, the pressure force of the measuring planes of the jaws on the end gauges should be the same everywhere. The measuring planes of the jaws are adjusted using three cast-iron laps, differing from one another in height by 0.25 mm. The laps are periodically adjusted and lubricated
Rice. 146. Method of checking pa - Fig. 147. Table stamp for
parallelism of the planes of the bending jaws of plate springs to
calipers using calipers
gauge tiles
apply 10-12 micron GOI paste moistened with kerosene. When assembling caliper assemblies, it is necessary to pay attention Special attention the operation of plate springs inserted into the grooves of the frame and clamp, since not only the smooth movement of the frame along the tool rod, but also the accuracy of monitoring the external and internal dimensions of the part with measuring jaws largely depends on them.
The planes of the rod ribs can be considered parallel to each other and perpendicular to the measuring planes of the jaws in the case when, when these planes come into contact with the cast block of end blocks and sharp jaws 7 and 8 and blunt jaws 5 and 6, the readings of the caliper will be the same.
When checking the parallelism of the planes of the jaws during the process of finishing them, it is necessary to ensure that screws 7 and 8 (Fig. 146) only lightly clamp the springs in frame 2 and clamp 9. This is done so that the frame and clamp move freely along the rod without distortions 1. At the same time, capturing right hand clamp 9 and frame 2, the patternmaker should only move them along the bar, and with his left hand, grabbing the slab of end measures 10, lightly swing it between the planes of blunt jaws 3 and 4 and sharp jaws 5 and 6.
By moving the tile along and across the planes of the jaws, they check not only the parallelism of their planes to each other, but also the fit of the planes of the tile W to the processed planes of the caliper jaws.
In Fig. 147 shows a diagram of a desktop hand stamp
for bending blanks of plate shaped springs made of steel 65G for rod tools. The matrix 2 of the stamp is clamped in a vice 1 and the blank of the leaf spring 3 is placed in it, then the shank 6 of the stamp is grabbed with the left hand and the punch 5, connected to the shank with pins 8, is pressed against the thrust bar 4, fixed to the matrix 2 with screws 7. Then the hammer handle easily hit the shank 6 of the stamp. The result is the required shape of a leaf spring of length L. Die dimensions
performed depending on the length of the frames and clamps of the rod tools.
In Fig. 148, and shows a method for correcting the curvature of the parallel side surfaces of the rod 2, fixed in a bench vice 1 between three aluminum spacers 3. In the process of straightening, the rod is moved with the left hand along the spacers 3, and with the right hand, turning the handle 4 of the vice and lightly pressing on the spacers, the bar curvature. In Fig. 148, b shows another method of straightening the curvature of a rod 2, clamped between aluminum spacers 5 in the jaws of a vice. Unlike the previous method, the curvature of the rod is corrected across its lateral planes using a fork-shaped mandrel 6.
The device shown in Fig. 149, intended for grinding and filing surfaces of caliper rulers. In the groove of the base 1, place a ruler 3 on the set screws 2 until it stops against the pin 4 and clamp it on both sides and at the end with screws 5 and 6. Using an indicator, check the parallelism of the surface, after which the device is tightened with a thicker end.
Push it onto the electromagnetic plate until it stops. Having sanded the surfaces of the ruler and sponge on one side, grinding wheel lift and, without changing the installation of the device, turn the ruler over and grind the surfaces on the other side. Then the caliper is assembled and the planes of its jaws and movable frame are adjusted.
When repairing the height gauge (Fig. 150, a), it is necessary to ensure that the rod is perpendicular to the base. Therefore, before straightening the rod 1, it is necessary to adjust the base 2 of the tool and check the perpendicularity of the rod with a square 3, secured with screws to a prism 4 mounted on the control plate 5.
When repairing the height gauge, you need to straighten and then adjust the sides of the rod (Fig. 150, 6) using the above devices. When finishing the lower work surface base 2 must be maintained perpendicular to its rod 1. In this case, the sides of the rod are adjusted together with the lower surface of frame 7. Before finishing the base, it is necessary to repair the frame and clamp 6, and if there are distortions, correct the leaf spring inserted into them. After repairing the frame 7 and finishing the sides of the rod, the latter is installed in the frame, checking the zero position on the scale of the vernier, secured with screws. Then the rod is turned over and installed again in the frame, ensuring that the zero marks of the rod and the vernier coincide.
Micrometers, like other types of measuring instruments and devices, are tested and certified for their suitability for use. In micrometric measuring instruments, in most cases, micrometer screws fail, the working planes of which require careful fine-tuning in this case.
Determination of readings by vernier
To determine the readings of a caliper, it is necessary to add the values of its main and auxiliary scales.
- The number of whole millimeters is counted on the bar scale from left to right. The pointer is the zero stroke of the vernier.
- To count fractions of a millimeter, it is necessary to find the vernier stroke that most accurately matches one of the strokes of the main scale. After this, you need to multiply the serial number of the found vernier stroke (not counting zero) by the value of its scale division.
The measurement result is equal to the sum of two quantities: the number of whole millimeters and fractions of mm. If the zero line of the vernier exactly coincides with one of the lines of the main scale, the resulting size is expressed as an integer.
The figure above shows the readings of the ShTs-1 caliper. In the first case they are: 3 + 0.3 = 3.3 mm, and in the second - 36 + 0.8 = 36.8 mm.
The instrument scale with a division value of 0.05 mm is presented below. For example, two different indications are given. The first is 6 mm + 0.45 mm = 6.45 mm, the second is 1 mm + 0.65 mm = 1.65 mm.
Similar to the first example, you need to find the strokes of the vernier and the rod that exactly match each other. In the figure they are highlighted in green and black, respectively.
Mechanical caliper device
The design of a double-sided caliper with a depth gauge is shown in the figure. The measurement range of this tool is 0-150mm. It can be used to measure both external and inner dimensions, hole depth accurate to 0.05 mm.
Essential elements
- Barbell.
- Frame.
- Sponges for external measurements.
- Sponges for internal measurements.
- Depth gauge ruler.
- Locking screw for fixing the frame.
- Vernier scale. Serves to count fractions of millimeters.
- Bar scale.
The jaws for internal measurements 4 are knife-shaped. Thanks to this, the hole size is determined on a scale without additional calculations. If the caliper jaws are stepped, as in the ShTs-2 device, then when measuring grooves and holes, their total thickness must be added to the readings obtained.
The reading value of the vernier may differ for different instrument models. So, for example, for ShTs-1 it is 0.1 mm, for ShTs-II it is 0.05 or 0.1 mm, and the accuracy of devices with a vernier reading value of 0.02 mm approaches the accuracy of micrometers. Design differences in the design of calipers can be expressed in the form of a moving frame, measurement ranges, for example: 0–125 mm, 0–500 mm, 500–1600 mm, 800–2000 mm, etc. The accuracy of measurements depends on various factors: the reading value on the vernier, work skills, and the good condition of the instrument.
The procedure for carrying out measurements, checking serviceability
Before work, check the technical condition of the caliper and, if necessary, adjust it. If the device has warped jaws, it cannot be used. Nicks, corrosion and scratches on working surfaces are also not allowed. It is necessary that the ends of the rod and the depth gauge ruler coincide when the jaws are aligned. The instrument scale must be clean and easily readable.
Measurement
- The caliper jaws are pressed tightly against the part with little force, without gaps or distortions.
- When determining the outer diameter of a cylinder (shaft, bolt, etc.), make sure that the plane of the frame is perpendicular to its axis.
- When measuring cylindrical holes, the jaws of the caliper are placed at diametrically opposite points, which can be found by focusing on the maximum scale readings. In this case, the plane of the frame must pass through the axis of the hole, i.e. Measurement along the chord or at an angle to the axis is not allowed.
- To measure the depth of a hole, a rod is placed at its edge perpendicular to the surface of the part. The depth gauge ruler is pushed all the way to the bottom using a movable frame.
- The resulting size is fixed with a locking screw and the readings are determined.
When working with a caliper, monitor the smooth movement of the frame. It should sit tightly on the bar without swaying, while moving without jerking with moderate force, which is regulated by the locking screw. It is necessary that when the jaws are aligned, the zero stroke of the vernier coincides with the zero stroke of the rod. Otherwise, reinstallation of the vernier is required, for which the screws securing it to the frame are loosened, the strokes are aligned and the screws are re-fastened.
Good day! Today we will talk about how to correctly take measurements using a universal measuring tool for this purpose - a caliper. With its help, you can determine the external/internal dimensions of parts, as well as the depth of holes.
The photo shows two instruments with vernier scale divisions of 0.1 and 0.02 mm.
Thanks to its special design, the tool allows you to fix the part, thus reducing the likelihood of an error occurring at the time of measurement.
Vernier caliper device:
- Barbell;
- Moving frame;
- Main scale;
- Sponges for measuring internal dimensions;
- Sponges for measuring external dimensions;
- Depth gauge;
- Vernier;
- Fixing (locking) screw.
When using a caliper, you should adhere to the following rules:
- The jaws must not be distorted.
- After the measurements have been taken, we fix the moving frame with a locking screw.
- While reading the readings, hold the caliper directly in front of your eyes.
- It is necessary to store the instrument in a special case, in a clean condition.
- After use, the tool must be wiped with a clean soft cloth.
Principles of measurement
Before starting measurements, we check the instrument for accuracy. To do this, let's bring the jaws of the caliper together. The zero marks, the tenth line on the vernier scale and the nineteenth line on the main scale must match.
Measuring external dimensions. Spread the caliper jaws a little more sizes the part being measured, and then bring them together until they stop, clamping the part.
Measuring internal dimensions. We set the tool to the zero position, then place the jaws in the required plane. Then we spread them all the way.
Depth measurement. We rest the end of the tool against the part and begin to move the moving frame until the depth gauge rests or reaches the desired point.
Performing markings. We set the specified value, fix the tool with a locking screw, rest one of the jaws against the edge of the part and apply markings to the surface of the workpiece (straight lines, notches, circles). But it is better to mark with tools specially designed for this purpose and spare an expensive, precise measuring instrument.
Reading the caliper readings
We count whole fractions of millimeters on the main scale to the zero mark of the vernier, and tenths (hundredths) of a millimeter - on the vernier scale starting from the zero mark to the first mark that matches the main scale.
A few examples:
How to properly store a tool
It is best to store the instrument in the case in which it is sold. Do not allow dust or sawdust to enter. Avoid contact with moisture and avoid accumulation of condensation. Avoid impacts and scratches, which may deform the instrument and reduce the measurement accuracy. After each use, wipe the surface with a dry cloth. The tool should be stored with the jaws spread apart (2-3 mm). Careful handling allows you to use it for many years and even decades.
In addition to the tools presented in this article, there are several other types of calipers:
Vernier caliper with a circular scale. In the recess located on the rod, there is a rack with a gear attached to it. The readings are read from a barbell and a dial scale.
Caliper with digital display.
I hope the information provided was useful! Thank you for your attention!
It just so happened (at least for the author) that the accuracy of measurements is made: with a ruler up to centimeters and a half, with a caliper up to millimeters, but tenths and hundredths of a millimeter are “caught” exclusively with the help of a micrometer. What prevents you from using a caliper to measure tenths of a millimeter, since that is what it is designed for, it will be difficult to answer “offhand”. Often, even those who know the structure of this measuring instrument will be careful to indicate the size recorded with a caliper with an accuracy of tens - because the scale (vernier) “responsible” for determining tenths of a millimeter is small in nature. I admit that it is for this reason that some calipers began to be produced equipped with a dial scale and even equipped with an electronic display (electronic).
What prevents you from upgrading a caliper you already use and thereby bringing the accuracy of its measurements closer to those of a dial caliper and, for example, equipping it with a magnifying glass? He sat down at the computer and began to draw a device that had already visited his imagination.
Refinement scheme
I made a cross-sectional sketch with numbers:
- 1 - the caliper rod is indicated
- 2 - movable caliper frame
- 3 - holder frame, it is installed on a movable frame
- 4 - screw securing the frame to the frame
- 5 - screw securing the frame with a magnifying glass to the frame
- 6 - magnifying glass frame
- 7 - spring pressing the frame to the head of the fastening screw
- 8 - magnifying glass
In accordance with the finished sketch, I collected the most suitable components of the future holder “piecemeal”.
In a textolite cube (in the past, some part of the body of an electronic device, and in the future, a holder frame), using a file, I enlarged the existing groove to a size corresponding to the movable frame of the caliper and drilled a hole with a diameter of 3 mm in the center for the fastening screw.
On the side there is an M4 threaded hole for a screw securing the frame with a magnifying glass. With the completion of the manufacturing of the frame, labor-intensive operations requiring precision and careful fitting come to an end.
A frame was made from a piece of soft plastic (in addition to the existing one). Two holes are drilled in the plastic plate. The smaller one is for the frame fastening screw, the larger one is for the existing frame (into which it is threaded, which makes it possible to adjust the sharpness).
The device is assembled according to the drawing. I didn’t specially cut the thread in the additional frame; it was made by the thread of the old (metal) frame when screwing it in for the first time. For this purpose, a soft plastic plate was selected, and the hole was made 0.5 mm smaller than necessary. It is clearly visible that the vernier marks (the name of the scale for determining tenths of mm) have been increased to a size that is more comfortable for observation. This makes it possible to confidently determine the measured size with an accuracy of “ten”. And even more than that - now you can easily distinguish a wire with a size of 0.85 mm from 0.80 mm using measurement.
The procedure for taking caliper readings
- count the number of whole millimeters; to do this, find on the rod scale the stroke closest to the left to the zero stroke of the vernier;
- they count fractions of a millimeter; for this, on the vernier scale they find the stroke closest to the zero division and coinciding with the stroke of the rod scale - its serial number will mean the number of tenths of a millimeter;
- add up the number of whole millimeters and fractions.
The device is easy to install and remove and can be used only when necessary. Author of the project - Babay iz Barnaula.
Discuss the article UPGRADE VERNIER CALIPS
This device is used to measure internal and external measurements, as well as between the surfaces of parts, used to measure the depth of holes and protrusions. has very useful function Compared to a mechanical one, it is adjusted to zero at any point on the scale, thanks to which deviations can be observed in each area of the size. That is, you can reset it to zero at, say, 21.55 mm, and then count the length from it.
In modern high-precision mechanical production there is no way to do without it. convenient tool, where the measurement range is universal. In heavy and light industry, construction, and in all other branches of technical life, it is no longer possible to imagine work without the use of a digital caliper. If necessary, a computer can be connected to the ES, to which all data will be output during the size control process. For this purpose, the digital caliper has a special connector:
The digital caliper has a resolution of 10 microns with an accuracy of 30 microns. This accuracy is achieved using capacitive sensors. Capacitive sensors very linear and immune to mechanical and electronic interference. However, they are sensitive to liquid. Accidentally entering liquid will unbalance the measuring bridges of the plates and increase the capacity.
How does a digital caliper work?
First, let's take this measuring device and see how it works from the inside.
The principle of its operation is a capacitive digital vernier, here is the technical documentation. The operation of a digital caliper is based on a capacitive matrix - an encoder.
Simply put, two “ordinary” capacitors connected in series, i.e. the top plate as a common electrode.
Electronic calipers use multiple plates to form a capacitive array that can accurately sense movement. There is a stator and a slider (“rotor”) plate. The stator is located in a metal ruler. And the moving part with the LCD screen has a slider.
Diagram of signals from capacitive sensors
Stator template fabricated into top layer copper standard glass epoxy laminate and bonded to stainless steel caliper bar. The slider pattern shown is similarly fabricated on a PC laminate, drives a 100 kHz signal through the sin/cos stator electrode plates and picks up AC voltage on two central pickup plates that describe the signals sin(displacement) and cos(displacement).
Separate sin and cos signals are needed to determine the direction of movement. The combination of analog interpolations between plates and a digital data processing circuit gives up to 0.02mm errors. Digital micrometers are used to measure with even higher accuracy. The device's power supply (LR-44 round battery) is enough for 2-4 months of daily operation. Based on the decrease in the contrast of the LCD indicator, it is clear that it is time to change it to a new one.
