In what cases is sawing of holes used? General concepts about fitting. Soldering, tinning, gluing
Fitting is the process of machining one part onto another in order to make a connection. For fitting, it is necessary that one of the parts is completely ready; the fitting is carried out on it. Fit is widely used in repair work ah, and also when assembling single products.
Fitting with a file is one of the most difficult jobs for a mechanic, since it has to be processed in hard to reach places. It is advisable to perform this operation with bur files, grinding bur heads, and using filing and cleaning machines.
When adjusting the liner to the finished hole, the work comes down to regular filing. When fitting according a large number Surfaces are first processed on two mating base sides, then the other two are adjusted until the desired mating is obtained. The parts should fit into one another without rolling, freely. If the product is not visible in the light, sawing is carried out along the paint.
Sometimes on adjusted surfaces and without paint you can discern traces of friction of one surface on another. Traces that look like shiny spots ("fireflies") show that this place interferes with the movement of one part over another. These places (protrusions) are removed, achieving either no shine or uniform shine over the entire surface.
During any fitting work, sharp edges and burrs must not be left on the parts; they must be smoothed with a personal file. How well an edge is smoothed can be determined by running your finger along it.
Fitting is the exact mutual fit of parts that are connected without gaps during any re-edging. The fitting is characterized by high processing accuracy, which is necessary for gap-free mating of parts (a light gap of more than 0.002 mm is visible).
Both closed and semi-closed contours are fitted. Of the two fitting parts, the hole is usually called the armhole, and the part included in the armhole is called the liner.
Armholes are open (Fig. 336) and closed (see Fig. 335). Fitting is carried out with files with fine and very fine cuts - No. 2, 3, 4 and 5, as well as abrasive powders and pastes.
When making and fitting templates with semicircular outer and inner contours, first a part with an internal contour is made - an armhole (1st operation) (Fig. 336, a). The liner is adjusted (fitted) to the treated armhole (Fig. 336.6) (2nd operation).
When processing an armhole, first the wide planes are accurately filed as base surfaces, then the edges (narrow edges) 1,2,3 and 4 are rough-cut, after which a semicircle is marked with a compass and cut out with a hacksaw (as shown by the line in the figure); make precise filing of a semicircular recess (Fig. 336, c) and check the accuracy of processing with the liner, as well as for symmetry with respect to the axis using a caliper.
When processing the liner, first saw down wide surfaces, and then ribs 1, 2 and 3. Next, mark and cut out the corners with a hacksaw. After this, precise filing and fitting of ribs 5 and 6 is carried out. Then precise filing and fitting of the liner to the armhole is performed. The accuracy of the fit is considered sufficient if the liner fits into the armhole without distortion, pitching or gaps (Fig. 336, d).
When making and fitting oblique liners and dovetail-type armholes (Fig. 337, h, 6), I first process the - * - liner (processing and checking it is easier). Processing is carried out in the following order (Fig. 337.6). First, the wide planes are accurately filed as base surfaces, then all four narrow edges (edges) 1, 2, 3 and 4. Next, sharp corners are marked (Fig. 337, c), cut out with a hacksaw and accurately filed. First, ribs 5 and 6 (Fig. 337, c, d) are filed in a plane parallel to edge 7, then ribs 7 and 8 (Fig. 337, a) along a ruler and at an angle of 60° to edge 4. Sharp corner(60°) is measured with an angular template.
The armhole is processed in the following order. First, the wide planes are accurately filed, after which all four edges are filed.
Next, marking is done, cutting a groove with a hacksaw (in Fig. 337,c shown with a dash) and filing ribs 5, 6 and 7. First, the width of the groove is made less than required by 0.05 - 0.1 mm while maintaining strict symmetry of the side ribs of the groove in relation to to the axis of the armhole, the depth of the groove is immediately accurate in size. Then, when fitting the liner and the armhole, the width of the groove is precisely measured according to the shape of the protrusion of the liner. The accuracy of the fit is considered sufficient if the liner fits tightly into the armhole by hand, without gaps, pitching or distortion (Fig. 337, e).
Manual sawing, fitting and fitting are very labor-intensive operations. IN modern conditions these operations are performed using metal cutting equipment general and special purpose, in which the role of a mechanic is reduced to operating machines and controlling dimensions.
Curvilinear and shaped parts are processed using grinding machines special profiled abrasive wheels. Wide Application electric spark, chemical and other processing methods are also found that eliminate additional manual finishing.
However, when performing metalwork, assembly, repair work, as well as during the final processing of parts obtained by stamping, these works have to be performed manually.
Application special tools and devices achieve increased cutting and fitting productivity. Such tools and devices include hand files with replaceable blades and wire files coated with diamond chips, filing prisms, filing marks, etc.
In the process of assembling parts into units and products, the jeweler repeatedly, each time before soldering, carries out their fitting - precise adjustment to each other (Fig. 5.12).
Tires are being fitted to castes, welts, overlays. Their fitting locations are determined design features decoration, but it is always necessary to observe certain patterns developed by practice, that is, to strictly maintain the lower and upper limits of combining parts. The lower limit in all cases is the location of the shank support platform and the base of the caste or welt at the same level. The upper limit may vary; in deaf castes it reaches the middle of the caste, in lateral smooth castes this limit is limited by the conventional line of the fastening belt, in openwork rim castes - by the height of the openwork and sometimes the fastening belts, in prong and corner castes - approximately by the middle of the prong or corner, and the welt - by the plane its surface.
The fitting process begins with sawing down the platforms - the notches on the castes or welts and the supporting platforms at the tires. The dimensions of the crossbars are dictated by the dimensions of the tires, or rather the dimensions of their supporting areas. To ensure high-quality fitting, the notches are made with a step, and the supporting platforms of the tires are sawn at the same angle as the notches.
When fitting blind rim (smooth and openwork) castes do everything from two opposite sides above the base, and one of the notches should be on the fugue in order to prevent the seam from diverging during soldering. When fitting cropanovy and most root caste notches are made on the welt, exactly opposite the prongs or corners, and the supporting platforms of the shanks are sawed down at the angle of the welt - pointed upward (towards the prong, corner). The shanks are soldered simultaneously to both the welt and the prong or corner, as if connecting the entire bunch together.
When fitting tops All the cuttings are done on the welt. In those cases when, due to the small height of the welt, it is impossible to make a notch, the shank is soldered simultaneously to the top and the welt, to do this, sawing off its support platforms in the form of a spike and fitting (inserting) them between the top and the welt at an angle that ensures high density fit. This fitting technique, additionally connecting the top to the welt, increases the reliability of the entire structure.
When fitting overlays it is necessary to proceed from their type: the overheads are soldered at one end to the top of the shank, and at the other to the wall of the caste without any notches; the inserted linings are supported with one end on the wall of the caste, and with the other (due to the notch) they are cut into the vinca.
Rack (checkbox) fit to the caste or welt exactly opposite the soldered hook; Use a file to make a corresponding slot, insert the stand into it and seal it. The soldering areas are cleaned.
Hooks they are inserted into a caste or welt by making a hole in the caste (by drilling or piercing) and inserting the end of a wire into it, or (in low castes) making a shallow notch (groove) with a file and soldering the end of the wire in it. In products with a low welt, the hook is inserted and soldered between the top and the welt. Often (in simple designs earrings) hooks are soldered without preliminary preparation all-overs and slots.
Study questions:
1. The essence of sawing and fitting.
2. Basic rules for sawing and fitting parts.
3. Typical defects when sawing and fitting parts, the reasons for their occurrence and methods of prevention.
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Discipline “Technology for performing plumbing work” College of ISTD (branch) NCFU in Pyatigorsk Oleg Yuryevich Goncharov, college teacher
Topic 11. Sawing and fitting 1. The essence of sawing and fitting. 2. Basic rules for sawing and fitting parts. 3. Typical defects when sawing and fitting parts, the reasons for their occurrence and methods of prevention. Study questions:
1. The essence of sawing and fitting Sawing is a type of filing. When sawing, a hole or opening is processed with a file to ensure the specified shape and size after this hole or opening has been previously obtained by drilling, drilling the contour with subsequent cutting out of jumpers, sawing out an open contour (opening) hand hacksaw, stamping, etc. A special feature of the sawing operation is quality control of processing (dimensions and configurations) is carried out using special testing tools - templates, workings, inserts, etc. (Fig. 1.1) along with the use of universal measuring instruments.
Continuation of question 1 Fig. 1.1. Template and insert: a - template; b - production; c - insert Fitting is a metalworking operation for mutual fitting by filing two mating parts (pairs). The fitted contours of pairs of parts are divided into closed (such as holes) and open (such as openings). One of the fitting parts (with a hole, opening) is called an armhole, and the part included in the armhole is called an insert.
2. Basic rules for sawing and fitting parts Rules for sawing 1. It is rational to determine the method of preliminary formation of sawed openings and holes: in parts with a thickness of up to 5 mm - by cutting out, and in parts with a thickness of over 5 mm - by drilling or reaming, followed by cutting out or cutting the jumpers. 2. When drilling, reaming, cutting out or cutting out jumpers, you must strictly monitor the integrity of the marking marks, leaving a processing allowance of about 1 mm. 3. A rational sequence for processing openings and openings should be observed: first process straight sections of surfaces, and then process the curved sections associated with them.
Continuation of question 2 4. The process of sawing openings and holes must be periodically combined with checking their contours against a control template, liner or working. 5. The corners of openings or holes must be processed clean with the edge of a file of the appropriate profile cross section(No. 3 or 4) or needle files, checking the quality of processing with workings. 6. The final processing of the hole surfaces should be done with a longitudinal stroke. 7. For final calibration and finishing of the hole, you should use notches, broaches and piercing on a screw or pneumatic press (Fig. 2.1). Rice. 2.1. Cylindrical firmware
Continuation of question 2 8. The work should be considered completed when the control template or liner completely, without rolling, enters the opening or hole, and the clearance (gap) between the template (liner, working) and the sides of the opening (hole) contour is uniform. Fitting rules: 1. Fitting two parts (pairs) to each other must be done in the following order: first, one part of the pair (usually with outer contours) - the liner - is manufactured and finished, and then using it, as if using a template, it is marked and fitted (fitted ) another mating part is the armhole. 2. The quality of fit should be checked by the clearance: in the gap between the parts of the pair, the clearance should be uniform. 3. If the contour of a pair of parts - the liner and the armhole - is symmetrical, they should mate without effort when turning 180°, with a uniform gap.
3. Typical defects when sawing and fitting parts, the reasons for their occurrence and methods of prevention Defect Cause Method of prevention Distortion of the opening or hole in relation to the base surface of the part Distortion during drilling or reaming. Insufficient control when sawing Carefully ensure that the tool is perpendicular to the base surface of the workpiece when drilling and reaming an opening (hole). During work, systematically check the perpendicularity of the plane of the opening (hole) being cut to the base surface of the part. Failure to comply with the shape of the opening (hole) Sawing was carried out without checking the shape of the opening (hole) according to the template (inlays). “Cuts” for markings when cutting out a contour First, cut along the markings (0.5 mm to the marking line). The final processing of the opening (hole) should be carried out by carefully checking its shape and dimensions measuring instruments or template (insert)
Continuation of 3 questions Mismatch of symmetrical contours of the fitting pair (liner and armhole) when they are turned 180° One of the parts of the pair (counter template) is not made symmetrically Carefully check the symmetry of the liner when marking and manufacturing One of the parts of the pair (armhole) is loose adjacent to the other (liner) in the corners. Blockages in the corners of the armhole. Observe the rules for processing parts. Cut through the corners of the armhole with a hacksaw or saw with a round file. The gap between the fitting parts is larger than permissible. Violation of the fitting sequence. Observe the basic rule of fitting: first, finally finish one part of the pair, and then fit the other one according to it.
Regional state budgetary professional educational institution
"Komsomolsk-on-Amur Aircraft Lyceum"
Training and production workshops
Sawing and fitting
Prepared by: Maria Saltanova
Head: Oleg Sergeevich Zanoskin, foreman industrial training
Sawing
is a type of filing. When sawing, a hole or opening is processed with a file to ensure the specified shape and size after this hole or opening has been previously obtained by drilling, drilling the contour with subsequent cutting out of jumpers, cutting out an open contour (opening) with a hand saw, stamping, or other.
Rice. 4.1. Template and insert:
A - sample;
b - production;
c - liner
Fitting
This is a metalworking operation for mutual fitting by filing two mating parts (pairs).
The fitted contours of pairs of parts are divided into closed(type of holes) and open(type of openings).
One of the fitting parts (with a hole, opening) is called armhole, and the part included in the armhole is insert .
Sawing rules
It is rational to determine the method of preliminary formation of sawed openings and holes: in parts with a thickness of up to 5 mm - by cutting out, and in parts with a thickness of over 5 mm - by drilling or reaming, followed by cutting out or cutting the jumpers.
Fitting rules:
The fitting of two parts (pairs) to each other should be carried out in the following order: first, one part of the pair (usually with external contours) - the liner - is manufactured and finished, and then, using it, as if using a template, the other mating part - is marked and fitted (fitted). armhole.
Typical defects when sawing and fitting parts
Defect
Cause
Distortion of the opening or hole in relation to the base surface of the part
Method of warning
Misalignment when drilling or reaming. Insufficient control when sawing
Failure to comply with the shape of the opening (hole)
Carefully ensure that the tool is perpendicular to the base surface of the workpiece when drilling and reaming an opening (hole). During work, systematically check the perpendicularity of the plane of the opening (hole) being cut to the base surface of the part
Sawing was carried out without checking the shape of the opening (hole) according to the template (inlays). “Gains” for markings when cutting out a contour
First, cut along the markings (0.5 mm to the marking line). The final processing of the opening (hole) is carried out by carefully checking its shape and dimensions with measuring tools or a template (liner)
Defect
Cause
Mismatch of symmetrical contours of the fitting pair (liner and armhole) when they are turned 180°
Method of warning
One of the parts of the pair (counter template) is not made symmetrically
One of the parts of the pair (armhole) does not fit tightly to the other (liner) in the corners
Debris in the corners of the armhole
Carefully check the symmetry of the liner when marking and manufacturing
The gap between the fitting parts is greater than permissible
Follow the rules for processing parts. Cut through the corners of the armhole with a hacksaw or saw with a round file.
Violation of the sequence of supplies
Observe the basic rule of fitting: first, finally finish one part of the pair, and then fit the other according to it
Purpose, types, essence, techniques and execution sequence
The fitting operations of metalworking include: fitting, fitting, lapping and finishing.
For fit One part to another, first of all, it is necessary that one of the parts be completely ready - the fitting is carried out according to it. The most significant obstacles to the fit of sliding parts are the sharp edges and corners of the sawn surfaces. They are adjusted until the mating parts fit into each other freely, without gap. If the connection is not visible in the light, nail it over the paint. On adjusted surfaces, even without paint, traces of friction from one surface to another may be visible. These marks, which look like shiny spots, show that it is these places that interfere with the movement of one part over another. Shiny areas (or traces of paint) are filed with a file until the part is finally ready. During any fitting work, sharp edges and burrs must not be left on the parts; they need to be smoothed with a file, as they can cause injury. The quality of processing of the ends and edges can be judged by running your finger over them.
The concept of “smoothing an edge” should not be confused with the concept of “chamfering”. When chamfering the edge of a part, a small flat strip is made, inclined at an angle of 45° to the side edges of the part.
By fitting is called mutual fit of parts that mate without gap. Both closed and semi-closed contours are fitted. The fitting is characterized by greater processing accuracy. In fitting parts, the hole is called an armhole, and the part included in the armhole is called an insert. Templates, counter-templates, stamping tools (punches and dies), etc. are subjected to fitting. The working parts of the template and counter-template must be fitted so that when the fitted sides of the template and counter-template come into contact, there is no gap between these sides for any of possible options mutual re-edging of the template and counter-template.
Lapping- processing of product surfaces by lapping, which is a tool made of soft materials with grinding powder. Using a lap, the thinnest layer of metal (up to 0.02 mm) is removed from the workpiece. The thickness of the metal layer removed by lapping in one pass does not exceed 0.002 mm. Grinding is carried out after work with a file or scraper for final finishing surface of the workpiece and giving it the greatest accuracy. Lapping is a very precise finishing finishing operation and is used to provide tight, sealed detachable and movable connections (connections of parts of taps, valves that hold liquids and gases well). The precision of grinding in parts is from 0.001 to 0.002 mm or until the mating surfaces completely coincide. The allowance for this operation is 0.01-0.02 mm. The grinding is done on a plate. Electrocorundum, emery (aluminum oxide), silicon carbide, crocus (iron oxide), chromium oxide, Vienna lime, tripoli, crushed glass, diamond dust, GOI pastes and other materials are used as abrasives. The most commonly used lubricants are engine oil, kerosene, gasoline, toluene, and alcohol.
To grind a part, a thin, even layer of abrasive powder mixed with oil is applied to the lapping plate. The part is placed with the ground surface on the plate and moved in a circular motion across the entire plate until a matte or glossy (shiny) appearance of the surface is obtained.
During the grinding process mechanical removal metal particles are combined with chemical reactions. When working with abrasive substances, the surface being treated is oxidized under the influence of the abrasive and oxygen in the air. By moving the lap, this film of oxidized metal is removed from the surface, but the surface immediately oxidizes again. In this way, the metal is removed until the surface acquires the required precision and cleanliness of processing.
Finishing performed on pre-polished surfaces, with an allowance left for finishing from 0.01 to 0.02 mm. Lapping is a type of lapping and is used to obtain not only the required shapes and surface roughness, but also the specified dimensions of parts with high accuracy. Finished surfaces are more durable, which is a determining factor for measuring and testing instruments and very precise parts.
Working tools and accessories
An important condition for high-quality processing of adjusted surfaces and holes is right choice files. Files are selected according to their cross-sectional profile depending on the shape of the processed surfaces and holes: for recesses and holes with square section- square files, for rectangular ones - flat and square files, for triangular ones - triangular, diamond-shaped and semicircular, for hexagonal holes - triangular and square. Files should have a width of the working part no more than 0.6-0.7 the size of the side of the recess or hole, the length of the file is determined by the size of the surface being processed (lengthwise) plus 200 mm. When processing curved surfaces of holes in the form of radius, oval or complex curved contours Round or semicircular files are used, in which the radius of curvature must be less than the radius of curvature of the contour being processed. Fitting is done with files with fine and very fine cuts - No. 2, 3, 4 and 5, as well as abrasive powders and pastes.
Also contributes to high-quality processing of parts correct selection fastening devices, such as hand vices, which allow you to quickly secure the workpiece. Their design allows the workpiece to be clamped in a vice with a conical device that opens and closes the jaws when rotating a round handle with a knurled surface. Oblique jaws for a vice are used for clamping parts when filing inclined surfaces and chamfering. The oblique jaws are inserted between the jaws of a conventional parallel bench vise.
Pattern vices are used to perform operations that require high positioning accuracy and reliable fastening of the part (when marking, drilling, reaming, flat and profile grinding). These vices differ from machine vices in their high manufacturing precision and the ability to install them on three mutually perpendicular planes. The fixed jaw is integral with the body. The design of the movable jaw allows it to move along the precisely ground plane of the body. In this case, the direction of the jaws is set by two keys. The movable jaw is held on the plane of the body by screws that pass through the distance stop and the bar.
The distance stop, when the screws are tightened, allows the parts to move in a sliding fit relative to the housing guides. The jaw is moved using a screw rotating in a nut, fixedly fixed to the body and locked in the movable jaw with a pin. The side surfaces of the pattern vice are strictly perpendicular to the ground base and parallel to each other, and the clamping planes of the jaws are perpendicular to the base and upper plane of the vice body. All main parts of the vice are made of U7A steel and subjected to heat treatment to hardness HRC 55-58 and grinding with tolerances of the second accuracy class. Clamps are widely used in fitting operations performed by a machinist. For example, a differential clamp screw has the following design. A differential clamping screw clamps a stack of plane-parallel parts and regulates both the parallelism of the jaws and the clamping force, which is especially important for pattern work.
The clamp has two clamping bars connected by two screws. The screw is differential, i.e. with two threads different diameters And different steps. The screw has a spring-loaded tip that self-aligns in the recess of the bar. This device allows you to first clamp the parts with a screw, and only then with a screw, which, with the small dimensions of the clamp, allows you to obtain reliable fastening with a significant clamping force.
To facilitate work and ensure higher precision in processing the edges of parts, mechanics use special devices, providing optimal installation workpiece, securely fastening it in the required position and creating an accurate direction for the processing tool (file, needle file, abrasive stone, lapping). Exist various designs devices: from the simplest filing square to complex frame devices with roller guides, protractors, sine rulers. To process straight surfaces of templates and patterns, parallels (marks) are used. The parallel with prismatic guide liners consists of two hardened and well-ground right-angle slats with grooves, which house two guide liners that fit tightly in the grooves. The slats move relative to each other and the workpiece is clamped using two screws.
For metalworking of internal right angles of templates, gauges and pattern tools, sliding squares are used. At manual processing templates, patterns and various gauges are used before and after hardening universal parallel. This device replaces several parallels used to process individual elements of the template profile. It consists of a housing, on the side surfaces of which there is a large number of holes with M6 threads. The holes are located in vertical and horizontal rows at a distance of 10 mm from each other. A strip with longitudinal groove, which serves as a guide plane along which the working tool moves. On the front side of the housing there is a vertical groove with a through slot along its entire length, in which a slider is placed that moves along the groove. In the desired position, the slider is secured with a screw located on the back side of the housing. In the upper part of the slide there is a through hole, the two faces of which form a prism. A screw is screwed into the end of the slide, with the help of which a pin, which serves as an axis, is pressed against the prism. The template to be processed is placed onto this axis using a technological hole when reproducing the arc sections of its profile. The diameter of the protruding part of the pin is 2 mm. Adjustment to a given radius is carried out by moving the slider along the groove while controlling the distance from the axis of the pin to the working plane of the device. Installation is carried out using a block of gauge blocks and using a straight edge.
