Filing is a cutting method in which a layer of material is removed from the surface of the workpiece using a file.
The file is multi-edged cutting tool, providing relatively high accuracy and low roughness of the machined surface of the workpiece (part).
By filing, parts are given the required shape and size, parts are adjusted to each other during assembly, and other work is performed. Using files, planes, curved surfaces, grooves, grooves, holes of various shapes, surfaces located at different angles, etc. are processed.
File(Fig. 1, A) is a steel bar of a certain profile and length, on the surface of which there is a notch
Fig.1. Files:
A- main parts (1 - handle; 2 - shank; 3 - ring; 4 - heel; 5 - edge;
6 - notch; 7 - rib; 8 - nose); b- single notch; V - double notch;
G - rasp notch; d - arc notch; e - pen attachment; and - Removing the file handle.
The notch forms small and sharp teeth, having a wedge-shaped cross section. For files with a notched tooth, the sharpening angle β is usually 70°, the rake angle γ is up to 16°, and the rear angle α is from 32 to 40°.
The notch can be single (simple), double (cross), rasp (point) or arc (Fig. 1, b - d).
Single cut files remove wide shavings, equal to the length the entire notch. They are used for filing soft metals.
Double cut files used when filing steel, cast iron and other hard materials, since the cross cut crushes the chips, which makes the work easier.
Files with rasp cut, Having spacious recesses between the teeth, which contributes to better placement of chips, very soft metals and non-metallic materials are processed.
Arc cut files have large cavities between the teeth, which ensures high performance and good quality processed surfaces.
Files are made from U13 or U13 A steel. After cutting the teeth, the files are subjected to heat treatment,
File handles usually made from wood (birch, maple, ash and other species). Techniques for attaching handles are shown in Figure 1. e And and.
According to their purpose, files are divided into the following groups: general purpose, special purpose, needle files, rasps, machine files.
Rice. 2. Shapes of file sections:
A And b- flat; V - square; G- triangular; d - round; e- semicircular;
and - rhombic; h - hacksaws.
Improving conditions and increasing labor productivity when filing metal is achieved through the use of mechanized (electric and pneumatic) files.
In training workshops, it is possible to use mechanized manual filing machines, which are widely used in production.
Universal grinder(see Fig. 4, G), powered by an asynchronous electric motor 1, has a spindle to which a flexible shaft is attached 2 with holder 3 for securing the working tool, and interchangeable straight and angular heads, allowing, using round shaped files, filing in hard to reach places and from different angles.
Metal filing
When filing, the workpiece is secured in a vice, and the surface to be filed should protrude 8-10 mm above the level of the jaws of the vice. To protect the workpiece from dents when clamping, jaws made of soft material. Working The posture when filing metal is similar to the working posture when cutting metal with a hacksaw.
With the right hand, take the handle of the file so that it rests against the palm of the hand, four fingers cover the handle from below, and the thumb is placed on top (Fig. 3, A).
The palm of the left hand is placed slightly across the file at a distance of 20-30 mm from its toe (Fig. 3, b).
Move the file evenly and smoothly over its entire length. The forward movement of the file is the working stroke. The reverse stroke is idle, it is performed without pressure. During the reverse stroke, it is not recommended to tear the file off the workpiece, as you may lose support and damage correct position tool.
Rice. 3. Grip the file and balance it during the filing process:
A- grip right hand; b- left hand grip; V - pressure force at the beginning of the movement;
G- pressure force at the end of the movement.
During the filing process, it is necessary to coordinate the efforts of pressing on the file (balancing). It consists of gradually increasing, during the working stroke, a slight initial pressure with the right hand on the handle while simultaneously decreasing the initially stronger pressure with the left hand on the toe of the file (Fig. 3, c, d).
The length of the file should exceed the size of the workpiece surface to be processed by 150-200 mm.
The most rational rate of filing is considered to be 40-60 double strokes per minute.
Filing As a rule, they begin with checking the processing allowance, which could ensure the manufacture of the part according to the dimensions indicated in the drawing. After checking the dimensions of the workpiece, determine the base, i.e. the surface from which the dimensions of the part should be maintained and mutual arrangement its surfaces.
If the degree of surface roughness is not indicated in the drawing, then filing is carried out only with a hog file. If it is necessary to obtain a more even surface, filing is completed with a personal file.
In practice manual processing The following types of filing occur in metals: filing of planes of mating, parallel and perpendicular surfaces of parts; filing curved (convex or concave) surfaces; sawing and fitting surfaces.
In the case of filing parallel flat surfaces, parallelism is checked by measuring the distance between these surfaces in several places, which should be the same everywhere.
When processing narrow planes on thin parts, longitudinal and transverse filing is used. When filing across the workpiece, the file comes into contact with a smaller surface, more teeth pass through it, which allows you to remove a large layer of metal. However, during cross-filing, the position of the file is unstable and it is easy to “fill up” the edges of the surface. In addition, the formation of “blockages” can be facilitated by the bending of a thin plate during the working stroke of the file. Longitudinal filing creates better support for the file and eliminates vibration of the plane, but reduces processing productivity.
For creating better conditions and increase labor productivity when filing narrow flat surfaces, special devices are used: filing prisms, universal basting marks, basting frames, special jigs and others.
The simplest of them is a frame mark (Fig. 4, a). Its use eliminates the formation of “blockages” on the treated surface. The front side of the basting frame is carefully processed and hardened to high hardness.
The marked blank is inserted into the frame, lightly pressing it with screws to the inner wall of the frame. The installation is clarified, ensuring that the marks on the workpiece coincide with the inner edge of the frame, after which the screws are finally secured.
Rice. 4. Filing of surfaces:
A - filing using a frame mark; b - method of filing convex surfaces; V - method of filing concave surfaces; G- filing using a universal grinding machine(1 - electric motor; 2 - flexible shaft; 3 - holder with tool).
Then the frame is clamped in a vice and the narrow surface of the workpiece is filed. Processing is carried out until the file touches the upper plane of the frame. Since this frame plane is processed with high accuracy, then the sawn plane will be accurate and will not require additional checking using a ruler.
When processing planes located at an angle of 90°, first the plane taken as the base is filed, achieving its flatness, then the plane perpendicular to the base. External corners are processed with a flat file. Control is carried out internal corner square The square is applied to the base plane and, pressing against it, is moved until it comes into contact with the surface being tested. The absence of clearance indicates that the perpendicularity of the surfaces is ensured. If the light slit narrows or widens, then the angle between the surfaces is greater or less than 90°.
Surfaces located at an angle of more or less than 90° are treated in the same way. External corners are processed with flat files, internal corners with rhombic, triangular and others. Processing control is carried out using protractors or special templates.
When processing curved surfaces, in addition to the usual filing techniques, special ones are also used.
Convex curved surfaces can be processed using the technique of rocking the file (Fig. 4, b). When moving the file, first its tip touches the workpiece, the handle is lowered. As the file advances, the toe lowers and the handle rises. During the reverse stroke, the movements of the file are opposite.
Concave curved surfaces, depending on the radius of their curvature, are processed with round or semicircular files. The file makes a complex movement - forward and to the side with rotation around its axis (Fig. 4, V). When processing curved surfaces, the workpiece is usually periodically re-clamped so that the processed area is located under the file.
Sawing is called processing of holes (armholes) of various shapes and sizes using files. In terms of the tools used and work methods, sawing is similar to filing and is its variety.
Files of various types and sizes are used for sawing. The choice of files is determined by the shape and size of the armhole. Armholes with flat surfaces and grooves are processed with flat files, and for small sizes - with square files. The corners in the armholes are sawed with triangular, rhombic, hacksaw and other files. Curvilinear armholes are processed with round and semicircular files.
Sawing is usually done in a vice. In large parts, the armholes are sawed at the installation site of these parts.
Preparation for sawing begins with marking the armhole. Then excess metal is removed from its internal cavity.
At large sizes the armholes and the greatest thickness of the workpiece, the metal is cut out with a hacksaw. To do this, drill holes in the corners of the armhole, insert a hacksaw blade into one of the holes, assemble the hacksaw and, stepping back from the marking line by the amount of sawing allowance, cut out the internal cavity.
By fitting is called the mutual fit of two parts that mate without gap. Both closed and semi-closed contours are fitted. The fitting is characterized by high processing accuracy. Of the two fitting parts, the hole is usually called, as when sawing, an armhole, and the part included in the armhole is called an insert.
Fitting is used as a final operation when processing parts of hinged joints and, most often, in the manufacture of various templates. Fitting is carried out using files with a fine or very fine notch.
The accuracy of the fit is considered sufficient if the liner fits into the armhole without distortion, pitching or gaps.
Possible types defects when filing metal and their causes:
Inaccuracy in the dimensions of the sawn workpiece (removal of a very large or small layer of metal) due to inaccurate markings, incorrect measurement or inaccuracy measuring tool;
Non-flatness of the surface and “blockages” of the edges of the workpiece as a result of the inability to correctly perform filing techniques;
Dents and other damage to the surface of the workpiece as a result of improperly clamping it in a vice.
Aircraft design defects. Aircraft design defects include all kinds of chips, microcracks, corrosion damage, etc. Defects are detected using non-destructive testing methods.
Cutting processing. Processing consisting in the formation of new surfaces by separating surface layers of material with the formation of chips. This is done by removing chips with a cutting tool (cutter, milling cutter, etc.)
Gluing processing. During repairs, adhesive compositions are used to restore parts with cracks and holes (cylinder blocks, crankcases, unit housings, containers, filters, etc.) for gluing damaged parts instead of riveting when repairing brakes, for leveling the surface of cabins and tail surfaces before painting as protective coatings to restore dimensions and geometric shape worn parts, eliminating scuffs and scratches in rubbing surfaces for the manufacture of repair parts from stamped blanks and non-metallic materials to ensure the strength and tightness of fixed joints.
Technological processes restoration of parts using adhesive compositions is characterized by ease of operation and does not require complex equipment. The use of adhesives allows the joining of homogeneous and heterogeneous materials, which is very difficult to achieve in other ways. When gluing the parts are not exposed to thermal and power loads, therefore, this method can restore parts of complex shapes and any size.
Welding processing. Welding in the repair industry is very wide application. Many defects and damage are eliminated by welding, including various cracks, chips, holes, thread breakage or wear, etc. Welding is the process of joining metal parts into one integral whole by heating the metal at the joints. When repairing automobile parts, the metal is heated gas flame or electric arc. Since parts are made from various metals (steel, gray and ductile iron, non-ferrous metals and alloys), the appropriate welding method is used. During hot welding, the part is slowly heated to a temperature of 600-650°C in special furnaces or furnaces. The higher the carbon content of cast iron, the slower the heating rate should be. Preheating is carried out during welding and welding of cracks in critical parts and parts of complex configurations. After heating, the part is placed in a thermally insulating casing with special valves or covered with sheet asbestos, leaving only the welding area open.
Soldering processing. Soldering is the process of obtaining a permanent connection or a hermetically sealed connection using filler materials - solders. When soldering, the base metal of the part does not melt. The reliability of the connection is ensured by the diffusion of solder into the metal and depends on correct selection flux and solder, thorough cleaning of the surface and the presence of a minimum gap at the junction of the connected parts. Depending on the melting point, solders are divided into soft and hard: soft solders have a melting point of up to 300 °C, and hard solders have a melting point of 800 °C and higher.
On-board emergency recorder is a device used in aviation to record basic flight parameters, indicators of aircraft systems, crew conversations, etc. to determine the causes of flight accidents. The flight recorder collects data such as:
o technical parameters: fuel pressure, pressure in hydraulic systems, engine speed, temperature, etc.;
o crew actions: degree of deflection of controls, cleaning and release of takeoff and landing mechanization, pressing buttons;
o navigation data: flight speed and altitude, course, passage of navigation beacons, etc.
Information is recorded either on magnetic media (metal wire or magnetic tape), or - in modern recorders - on solid-state drives (flash memory). This information can then be read and deciphered into sequential, time-stamped records.
Instrumentation and testing equipment. Instruments and devices for precise measurements include single- or double-sided calipers, standard and angular tiles, micrometers for external measurements, micrometer bore gauges, micrometer depth gauges, indicators, profilometers, projectors, measuring microscopes, measuring machines, as well as different types pneumatic and electrical devices and auxiliary devices.
Measuring indicators are designed for comparative measurements by determining deviations from a given size. In combination with appropriate devices, indicators can be used for direct measurements.
Measuring indicators, which are mechanical pointer instruments, are widely used to measure diameters, lengths, to check geometric shape, concentricity, ovality, straightness, flatness, etc. In addition, indicators are often used as component instruments and accessories for automatic control and sorting. The indicator scale division is usually 0.01 mm, in some cases – 0.002 mm. A variety of measuring indicators are minimeters and microcators.
Measuring devices are designed for measuring large-sized products.
Measuring projectors are devices belonging to the optical group, based on the use of the method of non-contact measurements, i.e., measuring the dimensions not of the object itself, but of its image reproduced on the screen at multiple magnification.
Measuring microscopes, like projectors, belong to the group optical instruments, which use a non-contact measurement method. They differ from projectors in that observation and measurement are made not on an image of the object projected on a screen, but on a magnified image of the object viewed through the eyepiece of the microscope. A measuring microscope is used to measure lengths, angles and profiles of various products (threads, teeth, gears, etc.).
Fuel filter maintenance. The main maintenance work of the fuel supply system is: washing the coarse filters; changing fine filter elements; checking the functionality of the fuel priming pump; checking and adjustment fuel pump high pressure on the beginning, magnitude and uniformity of fuel supply to the engine cylinders; setting the fuel injection advance angle; checking and adjusting injectors. Moreover, checking the fuel priming pump and the contamination of fuel filter elements must be systematic and carried out using instrumental methods (for example, using the KI-13943 GosNITI device).
Caring for fuel filters involves washing the coarse filter and changing the filter elements in the fine filters.
To wash the coarse filter, you need to drain the fuel from it and disassemble it. The filter element mesh and the internal cavity of the glass are washed with gasoline or diesel fuel and blown with compressed air.
Before replacing old filter elements with new ones, the fuel from the fine filters is drained and its glasses are washed with gasoline or diesel fuel and blown with compressed air.
After assembling the coarse and fine filters, you need to make sure that there is no air leakage through the filters when the engine is running. Air leaks and fuel leaks are eliminated by tightening the bolts securing the cups to the housings.
The fine filter is washed for ultrasonic unit in aqueous solution or creolin. The quality of filter washing in an ultrasonic installation is checked using the PKF device (Fig. 1.)
Picture 1.
Fig.1. Quality control of filter washing using the PKF device:
1 - signal button; 2- handle; 3, 8, 10 - sealing rings; 4 - body; 5 - float; 6- adapter; 7 - flange; 9 - filter being tested; 11 - plug; 12 - stopwatch). To do this, an adapter corresponding to the filter being tested is installed on the device, and a filter with one plug is installed on the adapter. AMG-10 oil is poured into the container, heated to a temperature of 18-23 ° C so that the oil level is 50...60 mm above the upper edge of the filter being tested. The filter is dipped into AMG-10 oil for a short time, after which the oil is allowed to drain. Prepare a stopwatch, plug the hole on the handle of the device, and lower the device with the filter into a container with AMG-10 oil. Open the hole on the handle of the device and turn on the stopwatch. At the moment the signal button coincides with the level of the upper end of the device handle, the stopwatch is turned off and the time for filling the filter with oil is determined, which should be no more than 5 s. If this time is more than 5 s, the filter is washed again using an ultrasonic unit or replaced.
Checking for leaks. The check is carried out as follows: first you need to turn on the compressor and observe the increase in pressure in the cabin using a mercury manometer. The rate of pressure rise should be no more than 0.3-0.4 mmHg. Art. When excess pressure in the cabin reaches 0.1 kgf/cm2, it is necessary to carry out an external inspection of the fuselage and identify places of air leakage, maintaining this pressure. Then slowly (no more than 0.3-0.4 mm Hg) bring the excess set in the cabin to 0.3 kgf/cm2, then turn off the air supply from the compressor; measure the time of drop of excess pressure from 0.3 to 0.1 kgf/cm2. The fuselage is considered airtight if the time it takes for the excess pressure to drop from 0.3 to 0.1 kgf/cm2 is at least 10 minutes. When checking the tightness (as the pressure increases and decreases), you should inspect possible leaks. If the pressure drop time is less than 10 minutes, it is necessary to check the contours of the hatches, front door, cockpit glazing, joints of the pressurized compartment skin (along the entire fuselage) and the nose wheel compartment. Additional leakage points may be sealed leads of electrical harnesses, pipes, SDGs and antennas. Elimination of identified defects should be carried out after bleeding the excess pressure to zero. Places with obvious leaks and air must be sealed, even if the pressure drop time is within the normal range.
Turboprop- a type of gas turbine engine in which the bulk of the energy from the hot gases is used to drive the propeller through a reduction gearbox, and only a small part of the energy is generated by the jet thrust exhaust. The presence of a reduction gearbox is due to the need to convert power: the turbine is a high-speed unit with low torque, while the propeller shaft requires relatively low speeds but high torque.
There are two main types of turboprop engines: twin-shaft, or free-turbine (the most common today), and single-shaft. In the first case, there is no mechanical connection between the gas turbine (called a gas generator in these engines) and the transmission, and the drive is carried out gas-dynamically. The propeller is not on a common shaft with the turbine and compressor. There are two turbines in such an engine: one drives the compressor, the other (through a reduction gearbox) drives the propeller. This design has a number of advantages, including the ability to operate the aircraft's power unit on the ground without transmission to the propeller (in this case, the propeller brake is used, and the operating gas turbine unit provides the aircraft with electrical power and high pressure air for on-board systems).
Because the efficiency of the propeller decreases as airspeed increases, turboprop engines are primarily found in relatively low-speed aircraft such as airlines and transport aircraft. At the same time, turboprop engines at low flight speeds are much more economical than turbojet engines.
PMD-70
Purpose.
The PMD-70 powder flaw detector is a universal multifunctional device that performs magnetic particle and magnetoluminescent methods of non-destructive testing of metal products and welded joints. The device is designed to detect various defects both on the surface of the part and in top layer ferromagnetic material.
PMD-70 is used to conduct flaw detection studies in industries that manufacture, service and operate metal constructions and products connected to each other by welding operations. The flaw detector is also effective in field conditions, when working outdoors and when testing in laboratories.
Operating principle.
The powder flaw detector has several varieties, differing in the type of magnetizing devices: electromagnets, cables, contact groups, and their power supply: from an alternating or direct current network. Using these devices and a pulse unit, the device induces an electromagnetic field in the controlled object, which magnetizes individual sections of the product with a longitudinal or circular field. Next, a magnetic suspension or powder is applied to the product, which is a kind of magnetization indicator. The presence and depth of damage is determined by the measured value of magnetic induction. By applying this indicator, a visual picture of the defect is created. Demagnetization of the product material occurs with the help of triggers that operate in dynamic mode and reverse the flow of current through magnetizing devices.
Conclusion
As a result of completing plumbing and mechanical practice, I:
Familiarized himself with safety precautions, labor protection when working with tools, equipment and devices for performing plumbing and mechanical work;
Acquired practical work skills as a performer of plumbing and mechanical work;
Consolidated the theoretical knowledge gained from studying special disciplines;
Familiarized himself with plumbing and mechanical equipment, tools and learned how to use them;
Familiarized himself with instruments and methods for detecting defects.
I would like to consider in detail, study the details of the aircraft and participate in maintenance. I hope to fill these gaps in the next field trip.
Tseulev N.E.
Ministry of Education and Science of the Republic of Kazakhstan
JSC Academy of Civil Aviation
Aviation Faculty
Department No. 10 " Aviation technology and flight operation"
TO category:
Metal filing
General techniques and filing rules
The product to be sawn is clamped in a vice so that the surface being processed protrudes above the jaws of the vice to a height of 5 to 10 mm. The clamp is made between the mouthpieces. The vice must be set according to the height of the worker and well secured.
When filing, you need to stand in front of the vice on the left or right, depending on need, turning 45° to the axis of the vice. The left leg is pushed forward in the direction of movement of the file, the right leg is moved 200-300 mm away from the left so that the middle of its foot is opposite the heel of the left leg.
Rice. 1. Filing: a – normal position of the body of the worker, b – diagram of the arrangement of the legs, c – position of the body of the worker during heavy filing
The file is taken in the right hand by the handle (Fig. 2), resting its head against the palm; The thumb is placed lengthwise on the handle, and the other fingers support the handle from below. Having placed the file on the object being processed, apply left hand palm across the file at a distance of 20-30 mm from its end. In this case, the fingers should be half-bent and not tucked in, as otherwise they can easily be injured by the sharp edges of the workpiece. The elbow of the left hand is raised. The right arm, from the elbow to the hand, should form a straight line with the file.
Rice. 2. Techniques for working with a file: a - position of the file handle in the right hand, b - filing, c - position of the left hand on the file
Hand actions when filing. The file is moved with both hands forward (away from you) and back (toward you) smoothly, along its entire length. As the file moves forward, it is pressed with your hands, but not equally. As he moves forward, the pressure of the right hand is increased and the pressure of the left is weakened (Fig. 3). When moving the file back, do not press it.
When filing planes, the file must be moved not only forward, but at the same time moved to the sides to the right or left in order to file off an even layer of metal from the entire plane. The quality of filing depends on the ability to regulate the pressure on the file; This skill is achieved only through practical filing work.
If you press the file with constant force, then at the beginning of the working stroke it will be deflected with the handle down, and at the end of the working stroke - with the front end down. When doing this type of work, the edges of the treated surface will “collapse”.
Methods of filing. The most difficult thing in filing is getting an evenly finished surface. The difficulty lies in the fact that the person doing the filing cannot see whether he is actually removing that layer of metal at the moment and in the place where it is necessary.
It is possible to file a plane correctly only if a file with a straight or convex, but not concave, surface is selected and if filing is performed by moving the file crosswise (with an oblique stroke), i.e., alternately from corner to corner. To do this, they first file, say, from left to right at an angle of 30-40° to the sides of the vice. After the entire plane has been traversed in this direction, it is necessary, without interrupting the work (so as not to lose the pace), proceed to filing with a straight stroke and then continue filing again with an oblique stroke, but from right to left. The angle remains the same. As a result, a network of cross strokes is obtained on the plane.
By the location of the strokes you can check the correctness of the processed plane. Let us assume that on a plane sawn from left to right, applying a straight edge reveals a bulge in the middle and a blockage along the edges. It is obvious that the plane was filed incorrectly. If you now continue filing by moving the file from right to left so that the strokes fall only on the convexity, then such filing will be correct. If strokes appear both on the convexity and on the edges of the plane, this will mean that filing is again being carried out incorrectly.
Finishing of the treated surface. Filing the surface usually ends with its finishing, which is done different ways. In metalworking, surfaces are finished with personal and velvet files, paper or linen abrasive sandpaper, and abrasive whetstones. Finishing with files is done with transverse, longitudinal and circular strokes.
In order to obtain a smooth and clean surface as a result of finishing, it is very important to avoid deep scratches on it during pre-finishing filing. Since scratches are caused by sawdust stuck in the file notch, it is necessary to clean the notch more often during operation and rub it with chalk or mineral oil. Even more carefully it is necessary to clean and rub with chalk or oil (and when filing aluminum - with stearin) the notch of finishing files, especially when working on viscous metals.
After finishing with a file, the surface is treated with abrasive stones or abrasive sandpaper (small numbers) dry or with oil. In the first case, a shiny metal surface is obtained, in the second - a semi-matte one. When finishing copper and aluminum, the skin should be rubbed with stearin.
Rice. 3. Distribution of the vertical clamping force of the right and left hands on the file (different pressure forces are shown by arrows, respectively different sizes);: a - at the beginning of the movement, b - in the middle of the movement, c - at the end of the movement
Rice. 4. Checking the file for straightness
Sanding a flat surface requires skill; Incorrect sanding can lead to damage to the product. To finish surfaces, wooden blocks with abrasive sand glued to them are also used. Sometimes the sandpaper is rolled onto a flat file (in one layer) or a strip of sandpaper is pulled onto the file, holding it while working, as shown in Fig. 7, e.
Rice. 5. Filing; a, b and c - successive positions of the worker, d - movement of the file during filing
When finishing a curved surface, as well as in those cases of finishing a straight surface, when a possible slight roll of the edges will not be considered a defect, the sandpaper is rolled onto a file in several layers.
Rice. 6. Finishing the surface with a file: a - transverse stroke, b and c - longitudinal stroke, d - circular stroke
Measurement and control during filing. To make sure that the plane is filed correctly, it is necessary to check it from time to time with a checking ruler for clearance. If the ruler lies tightly on the plane, without gaps, this means that the plane is sawed cleanly and correctly. If a gap that is even along the entire length of the ruler is indicated, the plane is sawn correctly, but roughly. Such a gap is formed because the notch of the file leaves thin grooves on the surface of the metal and the ruler rests on their tips.
Rice. 7. Finishing of sawn surfaces. a - wooden blocks with glued sandpaper, b - surface finishing of the part wooden block, c - abrasive paper sandpaper stretched on a file, d - finishing of the concave surface with abrasive sandpaper
On an incorrectly sawn plane, when applying a ruler, uneven gaps will be revealed.
Checking for clearance is carried out in all directions of the controlled plane: along and across and from corner to corner, i.e. diagonally. The ruler must be held with three fingers of the right hand - thumb, index and middle. You cannot move the ruler along the plane being checked: this will cause it to wear out and lose its straightness. To move the ruler, you need to lift it and carefully place it in a new place.
When checking with a square, it is carefully and firmly applied with the long side to the wide plane of the part; the short side is brought to the side being checked and looked at the light. If the part on this side is filed correctly, the short side of the square will lie tightly across the side of the part. If filing is incorrect, the square will touch either only the middle of the side side (if this side is convex), or some edges (if the side is oblique).
To check the parallelism of two planes, use calipers. The distance between parallel planes must be the same at any location. The caliper is held with the right hand by the joint washer. Setting the opening of the caliper legs to a certain size is done by lightly tapping one of the legs on some hard object.
The legs of the caliper must be installed on the parts so that their ends are opposite each other. If the legs are installed obliquely, offsets and tilts, incorrect results will be obtained during testing.
To check, set the opening of the caliper legs exactly according to the distance between the planes in any one place and move the caliper over the entire surface. If, when moving the caliper between its legs, a sway is felt, this means that in this place the distance between the planes is less; if the caliper moves tightly (without rolling), this means that the distance between the planes in this place is greater than in another.
The most common types of filing surfaces are: wide, narrow, angled, curved and cylindrical.
Before filing, as a rule, the processing allowance is checked: it is determined whether the dimensions of the workpiece are sufficient to complete the part according to the drawing.
After checking the dimensions of the workpiece, determine the base - the surface from which the dimensions and relative positions of the surfaces of the part should be maintained.
Flat surfaces, as you already know, are sawn flat. If the cleanliness of processing is not indicated on the drawing, the workpiece is processed only with a hog file.
Questions
The most difficult thing about filing is getting an evenly finished surface. The difficulty is that during filing it is not clear whether the desired layer of metal is being removed in a given place.
To file a wide surface, you need to select a flat file and process it with cross strokes, alternately from corner to corner. When filing, the teeth of a file leave marks on the surface being processed, called streaks. The cross-hatch filing technique is the most productive and allows you to obtain a more even surface.
Cross-filing as follows.
First, the entire surface is processed from left to right with a hog file, then with a straight stroke, and after that, without interrupting the work, they proceed to filing from right to left over the entire surface.
This is done alternately until the required layer metal The quality of filing is checked with a ruler or square.
After processing with a garnish file, finishing is carried out with a personal file, controlling the quality of processing with a ruler.
Question
“Plumbing”, I.G. Spiridonov,
G.P. Bufetov, V.G. Kopelevich
Curvilinear surfaces of machine parts are divided into convex and concave. Typically, filing such surfaces involves removing significant allowances. Before you begin processing, you should carefully mark the workpiece and choose the easiest way to remove excess metal. In one case it is necessary to first cut with a hacksaw, in another - to drill, in the third - to knock out. Excessively large allowance for filing...
Cylindrical rods sometimes have to be filed to reduce their diameter. It also happens that from the segment square section A cylindrical part is obtained by filing. Long blanks of rods from which a large layer of metal must be removed are clamped in a vice in a horizontal position and filed by swinging the file in a vertical plane and frequently turning the workpiece. Filing a long rod A short workpiece (rod) is clamped...
Before filing, the workpiece is clamped in a vice so that the surface to be processed is horizontal and protrudes 5-8 mm above the jaws of the vice. First, file one wide surface with a cross stroke, taking it as the main base. The sawn workpiece is removed. See the picture - Filing with a cross stroke. The quality of the processing is checked with a ruler, installing it along, across and diagonally...
Preparing the surface for filing. The workpiece is cleaned with metal brushes from dirt, oils, molding soil, scale, the foundry crust is cut off with a chisel or removed with an old file.
Securing the workpiece. The workpiece being processed is clamped in a vice with the sawing plane horizontally, 8-10 mm above the level of the jaws. The workpiece with treated surfaces is secured by placing jaws made of soft material (copper, brass, aluminum, mild steel) on the jaws.
Filing techniques. The position of the body is considered correct if an angle of 90° is formed between the shoulder and elbow parts of the right arm bent at the elbow with a file mounted on the jaws of the vice (initial position). In this case, the worker’s body must be straight and turned at an angle of 45° to the axis line of the vice.
Leg position. At the beginning of the working stroke of the file, the body weight falls on the right leg; when pressed, the center of gravity moves to the left leg. This corresponds to the following arrangement of legs: the left leg is carried (retracted) forward in the direction of movement of the file, the right leg is moved away from the left by 200-300 mm so that the middle of its foot is opposite the heel of the left leg.
During the working stroke of the file (pull), the main load falls on the left leg, and during the reverse (idling) stroke - on the right, so the leg muscles alternately rest.
When removing thick layers of metal with a file, the file is pressed with greater force, so the right leg is moved back half a step from the left and in this case it is the main support. When there is light pressure on the file, for example when finishing or finishing a surface, the feet are placed almost side by side. These precision jobs are often performed while sitting.
Hand position (file grip) is extremely important. The mechanic takes the file in his right hand by the handle so that it rests against the palm of his hand, four fingers clasp the handle from below, and the thumb is on top. The palm of the left hand is placed slightly across the file at a distance of 20-30 mm from its toe. In this case, the fingers should be slightly bent, but not drooping; they do not support, but only press the file. The elbow of the left hand should be slightly raised; right arm from the elbow to the hand - make a straight line with the file.
Coordination of efforts. When filing, it is necessary to maintain coordination of pressure forces (balancing). This consists in correctly increasing the pressure with the right hand on the file during the working stroke while simultaneously decreasing the pressure with the left hand. The movement of the file must be horizontal, so the pressure on its handle and toe must be changed depending on the position of the file’s fulcrum on the surface being processed. During the working movement of the file, the pressure with the left hand is gradually reduced. By adjusting the pressure on the file, you achieve a smooth sawn surface without blockages at the edges.
When the pressure is weakened with the right hand and increased with the left, the surface may collapse forward; when you increase the pressure with your right hand and weaken your left, you roll back.
You need to press the file against the surface being processed during the working stroke (from yourself). During the reverse stroke, you should not tear the file off the surface being processed: it should only slide. The rougher the processing, the greater the force during the working stroke.
When finishing filing, you should press the file much less than when roughing. In this case, with your left hand you press on the toe of the file not with your palm, but only with your thumb.
Sawing flat surfaces is a complex, labor-intensive process. Most often, a defect when filing such surfaces is a deviation from flatness. Working with a file in one direction makes it difficult to get a flat and clean surface.
Therefore, the direction of movement of the file, and therefore the position of the strokes (file marks) on the surface being processed should change alternately from corner to corner.
First, filing is performed from left to right at an angle of 30-40° to the axis of the vice, then, without interrupting work, with a straight stroke; finish filing with an oblique stroke at the same angle, only from right to left. This change in the direction of movement of the file provides the necessary flatness and roughness of the surface.
Control of the sawn surface. To control sawn surfaces, straight edges, calipers, squares and calibration plates are used.
The straight edge is selected depending on the length of the surface being checked, that is, the length of the straight edge should cover the surface being checked.
The quality of the surface filing is checked using a straight edge against the light. To do this, the part is released from the vice and raised to eye level; The straight edge is taken by the middle with the right hand and applied with its edge perpendicular to the surface being checked.
To check the surface in all directions, the ruler is first applied to the long side in two or three places, then to the short side (also in two or three places). And finally, along one and the other diagonal.
If the gap between the ruler and the surface being tested is narrow and uniform, then the plane has been processed satisfactorily.
To avoid wear, the ruler should not be moved across the surface; Each time it needs to be lifted and moved to the desired position.
Preparing the surface for filing. The workpiece is cleaned with metal brushes from dirt, oil, molding soil, scale, the foundry crust is cut off with a chisel or removed with an old file.
Consolidationblanks. The workpiece being processed is clamped in a vice with the sawing plane horizontally, 8...10 mm above the level of the jaws. The workpiece with treated surfaces is secured by placing jaws made of soft material (copper, brass, aluminum, mild steel) on the jaws.
Filing techniques. The position of the body is considered correct if an angle of 90° is formed between the shoulder and elbow parts of the right arm bent at the elbow with a file mounted on the jaws of the vice (initial position). In this case, the worker’s body must be straight and turned at an angle of 45 ° to the axis line of the vice .
Figure 5.2.1 Positions of arms (a), body (b) and legs (c) when filing.
Leg position. When the working stroke of the file begins, the mass falls on the right leg; when pressed, the center of gravity passes over the left leg. This corresponds to the following arrangement of legs: the left one is moved (retracted) forward in the direction of movement of the file, the right one is set back to the nose, from the left one by 200...300 mm so that the middle of its foot is opposite the heel of the left foot.
During the working stroke of the file (pull), the main load falls on the left leg, and during the reverse (idle) stroke - on the right, so the leg muscles alternately rest.
When removing thick layers of metal, you have to press the file with great force, so the right leg is moved back half a step from the left and in this case it is the main support. When there is light pressure on the file, for example when finishing or finishing a surface, the groans of the legs are located almost next to each other. These jobs, like precision ones, are often performed while sitting.
Figure 5.2.2. File grip: a - with the right hand; b - left hand
Hand position(file grip) is extremely important. The mechanic takes the file by the handle in his right hand so that the latter rests against the palm of the hand, four fingers grip the handle from below, and the thumb is placed on top (Figure 5.2.2 a). The palm of the left hand is placed slightly across the file at a distance of 20...30 mm from its toe (Figure 5.2.2 b). In this case, the fingers should be slightly bent, but not drooping; they do not support, but only press the file. The left elbow should be slightly raised. The right arm from the elbow to the hand should form a straight line with the file (Figure 5.2.1 a).
Figure 5.2.3. Coordination of efforts during filing
Coordination of efforts. When filing, coordination of pressure forces (balancing) must be observed, which consists in correctly increasing the pressure with the right hand on the file during the working stroke while simultaneously decreasing the pressure with the left hand. The movement of the file should be horizontal, so the pressure on its handle and toe should vary depending on the position of the file’s fulcrum on the surface being processed. During the working movement of the file, the pressure with the left hand is gradually reduced. By adjusting the pressure on the file, you achieve a smooth filing surface without blockages at the edges.
If the pressure is weakened by the right hand and increased by the left, the surface may collapse forward. If you increase the pressure with your right hand and loosen your left, you will end up with a backward tilt.
It is necessary to press the file against the surface being processed during the working stroke (from yourself). During the reverse stroke, do not tear the file off the surface being processed. During the reverse stroke, the file should only slide. The rougher the processing, the greater the force on the working stroke.
When finishing filing, the pressure on the file should be significantly less than when roughing. In this case, with your left hand you press on the toe of the file not with your palm, but only with your thumb.
Filing surfaces is difficult labor-intensive process. The most common defect when filing surfaces is deviation from flatness. Working with a file in one direction makes it difficult to get a flat and clean surface. Therefore, the direction of movement of the file, and therefore the position of the strokes (file marks) on the surface being processed must change, alternately from corner to corner.
Figure 5.2.4 Filing: a - from left to right; b, c - across and along the workpiece; from right to left
First, filing is performed from left to right at an angle of 30...40 0 to the axis of the vice, then, without interrupting work, with a straight stroke; finish filing with an oblique stroke at the same angle, but from right to left. This change in the direction of movement of the file ensures that the required flatness and surface roughness are obtained.
