the workpiece must be securely installed and firmly fixed;

defective scrapers are not allowed to work (without handles or with cracked handles);

when working with grinding heads, observe the electrical safety rules.

CUTTING AND FILLING

51. Sawing

Sawing is the processing of holes in order to give them the desired shape. The processing of round holes is made by round and half-round files, triangular - by three-edged, hacksaw and rhombic files, square - by square files.

Sawing in the workpiece square hole.    First, mark the square, and in it - the hole, then drill the hole with a drill, whose diameter is 0.5 mm less than the side of the square.

Further processing of the sides is carried out until the square head is light, but does not fit tightly into the hole.

Sawing in the workpiece triangular holes.    They mark the contour of the triangle, and in it - the hole and drill it with a drill, without touching the marking marks of the triangle. The gap between the sides of the triangle and liners when checking the probe should be no more than 0.05 mm.

52. Fit and fit

By fit called the processing of one part on another in order to perform the connection. This operation is widely used in repair work, as well as in the assembly of individual products.

When any fitting work can not leave sharp edges and burrs on the details, they need to smooth out a personal file. How well the edge is smoothed can be determined by tracing it with your finger.

By fitting    is called the exact mutual fitting of parts, connecting without gaps in any reverses. It is done by fitting files with small and very small notches - № 2, 3, 4 and 5, as well as abrasive powders and pastes.

In the manufacture and fitting of templates with a semicircular outer and inner contours, first produce a part with an inner contour - armhole. To the treated armhole customized (fit) insert.

Manual sawing, fitting and fitting are very time consuming operations. However, when performing assembly and repair work, as well as during final processing of parts obtained by stamping, it is necessary to perform these works manually. The use of special tools and accessories (manual files with interchangeable plates, files from wire covered with diamond chips, filler prisms, etc.) increases the productivity of work when sawing and fitting.

BREAST AND ARRAY

  53. General information. Lapping materials.

General information. Lapping    called processing of parts working in pairs, to ensure the best contact of their working surfaces.

  Fine-tuning    - it is a finishing treatment of parts in order to obtain accurate dimensions and low surface roughness.

The lapping and finishing are carried out by abrasive powders or pastes applied to the surfaces to be treated, or a special tool, the lapping.

The allowance for grinding is 0.01 ... 0.02 mm, for fine tuning - 0.001 ... 0.0025 mm.

The accuracy of lapping is 0.001 ... 0.002mm. Lapping provides accuracy to 5 ...

... 6 qualities and roughness up to Rz 0.05.

Hydraulic pairs, valves and saddles in internal combustion engines, working surfaces of measuring instruments are lapped.

Lapping materials. Abrasive materials    (abrasives) are fine-grained crystalline powdered or massive solids used for machining materials.

Abrasives are divided into natural and artificial, and distinguished by hardness.

Hard Natural Abrasives    - These are minerals containing aluminum oxide (emery) and silicon oxide (quartz, flint, diamond).

Hard artificial abrasives   - get in electric furnaces, have high hardness and uniformity of composition. These include: electrocorundum - normal (1A); white (2A); chromium (3A); monocorundum (4A); silicon carbides (carbocorund) green (6C); black (5C); boron carbide (kb); cubic boron nitride (KBN); elbor (L); synthetic diamond (AC). Used in the processing of cast iron, brittle and difficult materials.

Soft abrasive materials    - micro powders M28, M20, M14, M10, M7, M5 and GOI pastes. Used for final finishing work.

Diamond paste    - natural and synthetic have twelve grains divided into four groups having each its own color:

coarse grain (AP100, AP80, AP60) red;

medium grain (AP40, AP28, AP20) green;

fine grain (AP14, AP10, AP7) blue;

fine grain (AP5, AP3 and AP1) yellow.

Diamond pastes use the proportion of grinding and finishing products from hard alloys, steels, glass, ruby, ceramics.

The consistency of diamond paste is divided into solid, oily and liquid .

Lubricants    for grinding and finishing, they accelerate these processes, reduce roughness, and also cool the surface of the part. For lapping (finishing) of steel and cast iron, kerosene is more often used with the addition of 2.5% oleic acid and 7% rosin, which significantly improves the productivity of the process.

54. Cleaners

Lapping is performed with a special tool - priter, the shape of which should correspond to the shape of the surface to be treated.

Flat lapping    are cast iron plates, which bring the plane. Flat ground for pre-treatment has grooves with a depth and width of 1 ... 2 mm, located at a distance of 10 ... 15 mm, in which the remains of abrasive material are collected. Grounding for final finishing make smooth.

Cylindrical lap    used for finishing cylindrical holes. Such lapings are (a) unregulated and (b) -regulated. Regulation of the diameter of the priter is carried out with nuts.

Cartoons grinding in hard abrasive material.    There are two ways - direct and indirect.

With direct mode   the abrasive powder is pressed into the lap to work. Round grinding with a diameter of more than 10 mm is carcassed on a hard steel plate, on which an abrasive powder is poured with a thin, even layer.

After caricaturing, the rest of the abrasive powder is removed with a hair brush, the lap is slightly lubricated and used for work.

Indirect way It consists in coating the lap with a layer of lubricant, which is then sprinkled with an abrasive powder.

Add new abrasive powder during operation should not be, as this leads to a decrease in the accuracy of processing.

Ground materials. Prints made of cast iron, bronze, copper, lead, glass, fiber and hardwood, oak, maple, etc. For the finishing of steel parts, it is recommended to make lap-joints from medium-hard cast iron (HB 100 ... 200), for thin and long lapping use Steel St2 and St3 (HB 150 ... 200). Steel lap wears out faster than cast iron ones, therefore they are lubricated with GOI pastes in order to obtain a mirror surface.

Methods of lapping and finishing.    For productive and accurate lapping, it is necessary to properly select and strictly dose. amount of abrasive materials  as well as lubricants. When lapping it is necessary to consider   pressure on the parts to be ground  . Typically, the pressure at lapping is 150 ... 400kPa (1.5 ... 4kgs / cm). At the final lapping pressure must be reduced.

Lapping flat surfaces    usually produced on fixed cast iron finishing plates. Lapping on the plates gives very good results, so they are processed parts that require high precision machining (patterns, gauges, tiles, etc.).

Preliminary fine-tuning is carried out on a plate with grooves, and the final one - on a smooth plate in one place, using only the remnants of the powder that has remained on the part from the previous operation.

Quality control refinement.    After finishing the surface, check for paint (on a well-finished surface). The plane when fine-tuning is controlled with a curved ruler with an accuracy of 0.001mm. It should be borne in mind that in order to avoid control errors, all measurements should be carried out at 20 C.

Safety.    When performing lapping and finishing work it is necessary: ​​to clean the surface to be treated not with your hand, but with a rag; handle with pastes carefully, as they contain acids; comply with safety requirements when working with a mechanized tool, as well as on machine tools.

PAIKA, PEOPLE, BONDING

55.General information about soldering. Solders and fluxes

  General information. Soldering   - is the process of obtaining permanent connection of materials with heating below the temperature of their autonomous melting by wetting, spreading and filling the gap between them with molten solder and their adhesion during the crystallization of the seam. Soldering is widely used in various industries.

The advantages of soldering include: slight heating of the connecting parts, which preserves the structure and mechanical properties of the metal; preserve the size and shape of the part; bond strength.

Modern methods allow soldering carbon, alloyed and stainless steels, non-ferrous metals and their alloys.

  Solders -   This quality, durability and operational reliability of the soldering connection. Solders should have the following properties:

have a melting point below the melting point of brazing materials;

Study questions:

??one. 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 of performance of metalworking" College ISTiD (branch) of NCFU in Pyatigorsk Goncharov Oleg Yuryevich College teacher

Theme 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 Cutting is a type of sawing. When sawing, the file is processed by a hole or opening to ensure a given shape and size after this hole or opening is preliminarily obtained by drilling, drilling the contour, followed by cutting down the bridges, cutting the open loop (opening) with a manual hacksaw, punching, or other. quality control of processing (size and configuration) is performed by special testing tools - templates, workings, inserts, etc. (Fig. 1.1) along with the use of universal measuring instruments.

Continuation of 1 question Fig. 1.1. Template and liner: a - template; b - development; c - liner Fitting is a metalworking operation for mutual fitting with the methods of filing two mating parts (pair). Fitting contours of pairs of parts are divided into closed (like holes) and open (like openings). One of the fitting parts (with a hole, aperture) is called the armhole, and the part entering 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 pre-formation of sawn openings and holes: in details up to 5 mm thick, by cutting, and in details over 5 mm thick, by drilling or boring, followed by cutting or cutting jumpers. 2. When drilling, reaming, cutting down or cutting jumpers, it is necessary to strictly monitor the integrity of marking markers, leaving allowance for processing of about 1 mm. 3. A rational sequence of processing openings and holes should be observed: first, treat straight parts of surfaces, and then curvilinear sections connected with them.

Continuation of question 2 4. The process of sawing openings and holes must be periodically combined with checking their contours with a control pattern, liner or development. 5. The corners of the openings or holes must be cleaned with the file edge of the corresponding cross-sectional profile (No. 3 or 4) or with files, checking the quality of the workings with the workings. 6. The final treatment of the surfaces of the holes should be done with a longitudinal stroke. 7. For the final calibration and finishing of the hole, you should use cuts, pulling and piercing on a screw or pneumatic press (Fig. 2.1). Fig. 2.1. Cylindrical firmware

Continuation of question 2 8. The work should be considered completed when the control template or liner is completely, without rolling, enters the opening or hole, and the clearance (clearance) between the template (insert, output) and the sides of the contour of the opening (opening) is uniform. The fitting rules: 1. The fitting of two parts (a pair) to each other should be done in the following order: first, one piece is made and finished (usually with outer contours) - the liner, and then, as a template, it is laid out and fitted (fitted) ) another mated part - armhole. 2. The quality of fitting should be checked for clearance: in the gap between the parts of a pair, the clearance should be uniform. 3. If the contour of a pair of parts - liner and armhole - is symmetrical, they must mate with a uniform clearance when transforming through 180 °.

3. Typical defects when sawing and fitting parts, the reasons for their occurrence and methods of warning. Defect Cause Method of warning. Distortion of the opening or hole with respect to the base surface of the part. Distortion during drilling or drilling. Inadequate control when sawing Carefully monitor the tool perpendicularity of the base surface of the workpiece when drilling and reaming the hole (hole). In the course of work, systematically check the perpendicularity of the plane of the sawed opening (hole) of the base surface of the part. Non-compliance with the shape of the opening (hole) Cutting was performed without checking the shape of the hole (hole) using a template (shu contributions). “Notches” for marking when you are cutting a contour First, sawing should be performed according to the marking (0.5 mm to the marking line). Final processing of the opening (opening) should be carried out with a thorough check of its shape and size with measuring tools or a template (insert).

Continuation of 3 questions Disagreement of symmetrical contours of the fitted pair (liner and armhole) when re-styling by 180 ° adjacent to the other (liner) in the corners Zavaly in the corners of the armhole Follow the rules for processing parts. Cut with a hacksaw or with a round file cut the corners of the armhole. The gap between the parts to be fitted is more than permissible. Disturbance of the fixing.

Fit is called machining one part over another in order to complete the connection. For a fit, it is necessary that one of the parts is completely finished, fitting on it. Fit is widely used in repair work, as well as in the assembly of individual products.

Fitting a file is one of the most difficult in the work of a locksmith, as you have to handle in hard-to-reach places. It is advisable to carry out this operation bornapilniki, grinding borgolovkami, using filing and stripping machines.

When fitting the liner to the finished hole, the work is reduced to the usual filing. When fitting over a large number of surfaces, the two mating base sides are first treated, then the other two are adjusted to the desired conjugation. Details must enter one into the other without pitching, freely. If the product is not visible on the lumen, they lead on the paint.

Sometimes traces of friction of one surface over another can be distinguished on customized surfaces and without paint. Traces that look like shiny spots ("fireflies") show that this place interferes with the movement of one part over the other. These places (protrusions) are removed, achieving or lack of gloss, or uniform gloss over the entire surface.

When any fitting work can not leave sharp edges and burrs on the details, they need to smooth out a personal file. How well the edge is smoothed can be determined by tracing it with your finger.

Fitting is the exact reciprocal fit of the parts, connecting without gaps in any beats. The fitting is characterized by high processing accuracy, which is necessary for backlash-free coupling of parts (the light gap of more than 0.002 mm is visible).

Both closed and semi-closed circuits are fitted. Of the two parts to be fitted, it is accepted to call the hole an armhole, and the part entering the armhole is an insert.

Arms are open (Fig. 336) and closed (see Fig. 335). It is done by fitting files with small and very small notches - № 2, 3, 4 and 5, as well as abrasive powders and pastes.

In the manufacture and fitting of templates with semicircular outer and inner contours, at first, a part with an inner contour is made - an armhole (1st operation) (Fig. 336, а). To the treated armhole, they fit (fit) the liner (Fig. 336.6) (2nd operation).

When processing the armholes, at first, wide planes are precisely sawn off as base surfaces, then, in outline, the edges (narrow faces) 1,2,3 and 4, then the semicircle is marked with compasses, cut out with a hacksaw (as shown in dashed figure); make an exact filing of a semicircular recess (Fig. 336, c) and check the accuracy of processing with the insert, as well as for symmetry with respect to the axis using calipers.

When processing the liner, they first saw wide surfaces, and then the ribs 1, 2 and 3. Next, cut corners and cut with a hacksaw. After that, an exact filing and fitting of the fins 5 and 6 are carried out. Then, an exact filing and fitting of the liner to the armhole are performed. The accuracy of fitting is considered sufficient if the liner enters the armhole without tilting, pitching and gaps (Fig. 336, d).

In the manufacture and fitting of oblique inserts and doray-type armholes (Fig. 337, з, 6), I first process - * - the liner (processing and testing it is easier). Processing is carried out in the following order (Fig. 337.6). At first, wide planes are precisely sawn off as base surfaces, then all four narrow edges (edges) 1, 2, 3 and 4. Next, mark sharp corners (Fig. 337, c), cut them with a hacksaw and accurately cut them. First, edges 5 and 6 are filed (Fig. 337, c, d) in a plane parallel to edge 7, then edges 7 and 8 (Fig. 337, a) along a ruler and at an angle of 60 ° to edge 4. The acute angle (60 ° ) measured angular pattern.

The cross-section is processed in the following order. At first, wide planes are precisely sawn, and then all four edges are sawn.

Next, the groove is cut, a hacksaw is cut (in Fig. 337, shown in strokes), and the fins 5, 6 and 7 are filmed. 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 groove width gets the exact size according to the shape of the protrusion of the liner. The accuracy of fitting is considered sufficient if the liner enters the armhole tightly by hand, without gaps, pitching and distortions (Fig. 337, e).

Manual sawing, fitting and fitting are very labor-intensive operations. In modern conditions, these operations are performed using metal-cutting equipment for general and special purposes, in which the role of locksmith is reduced to machine control and dimensional control.

Curvilinear and shaped parts are processed on grinding machines with special profiled abrasive wheels. Electrospark, chemical and other processing methods that exclude additional finishing manually are also widely used.

However, when performing assembly and repair work, as well as during final processing of parts obtained by stamping, it is necessary to perform these works manually.

The use of special tools and devices to improve the performance of sawing and fitting. Such tools and devices include manual files with interchangeable blades and files from wire covered with diamond chips, filing prisms, filing basting, etc.

  Fit and Fit

TO  category:

Glare, lapping, etc.

Fit and Fit

Fit is called machining the part over another in order to complete the connection. For a fit, it is necessary that one of the parts is completely finished, fitting on it. Fit is widely used in repair work, as well as in the assembly of individual products.

Fitting a file is one of the most difficult in the work of a locksmith, as you have to handle in hard-to-reach places. It is advisable to carry out this operation Borna-pilnik, grinding borgolovkami, using filing and stripping machines.

When fitting the liner to the finished hole, the work is reduced to the usual filing. When fitting to a large number of surfaces, the two mating base sides are first processed, then the other two are fitted to obtain the desired pairing. Details must enter one into the other without pitching, freely. If the product is not visible on the lumen, they lead on the paint.

Fig. 1. Sawing a square hole: a - marking, b - taking sawing

Sometimes traces of friction of one surface over another can be distinguished on customized surfaces and without paint. Traces that look like shiny spots (“fireflies”) show that this place interferes with the movement of one part over the other. These places (protrusions) are removed, achieving or lack of gloss, or uniform gloss over the entire surface.

When any fitting work can not leave sharp edges and burrs on the details, they need to smooth out a personal file. How well the edge is smoothed can be determined by tracing it with your finger.

Fitting is the exact reciprocal fit of the parts, connecting without gaps in any beats. The fitting is characterized by high processing accuracy, which is necessary for backlash-free coupling of parts (the light gap of more than 0.002 mm is visible).

Both closed and semi-closed circuits are fitted. Of the two parts to be fitted, it is accepted to call the hole an armhole, and the part entering the armhole is an insert.

Armholes are open and closed. It is done by fitting files with small and very small notches - № 2, 3, 4 and 5, as well as abrasive powders and pastes.

In the manufacture and fitting of templates with semicircular outer and inner contours, a part with an inner contour is first made - an armhole (1st operation). To the treated armhole customized (fit) insert (2nd operation).

When processing the armholes, at first, wide planes are precisely sawn off as base surfaces, then, in rough outline, the edges (narrow faces) 1, 2, 3 and 4, then the semicircle is marked with compasses, cut out with a hacksaw (or shown with a dash in the figure); make an exact filing of a semicircular recess and check the accuracy of processing with the liner, as well as for symmetry with respect to the axis with the help of calipers.

When processing the liner, they first saw wide surfaces, and then the ribs 7, 2 and 3. Then the corners are marked and cut with a hacksaw. After that, an exact filing and fitting of the fins 5 and 6 are carried out. Then, an exact filing and fitting of the liner to the armhole are performed. The accuracy of fitting is considered sufficient if the liner enters the armhole without tilting, pitching and gaps (Fig. 336, d).

In the manufacture and fitting of oblique inserts in the doym-type armholes, the liner is first treated (processing and testing it is easier). Processing are in the following order. At first, wide planes are precisely sawn off as base surfaces, then all four narrow edges (edges) 7, 2, 3 and 4. Next, mark sharp corners, cut them with a hacksaw and accurately cut them. First, the ribs are sawn in a plane parallel to the rib 7, then the ribs 7 and 8 along the ruler and at an angle of 60 ° to the edge 4. The sharp angle (60 °) is measured with an angular pattern.

The cross-section is processed in the following order. At first, wide planes are precisely sawn, and then all four edges are sawn.

Next, the groove is cut, grooved with a hacksaw, and the edges 5, 6 and 7 are filmed. First, the groove width is made less than required by 0.05-0.1 mm while maintaining the strict symmetry of the side edges of the groove with respect to the axis of the armhole, the groove depth is immediately accurate size. Then, when fitting the liner and the armhole, the groove width gets the exact size according to the shape of the protrusion of the liner. The accuracy of fitting is considered sufficient if the liner enters the armhole tightly by hand, without gaps, pitching and warps.

Manual sawing, fitting and fitting are very labor-intensive operations. In modern conditions, these operations are performed using metal-cutting equipment for general and special purposes, in which the role of locksmith is reduced to machine control and dimensional control.

Curvilinear and shaped parts are processed on grinding machines with special profiled abrasive wheels. Electrospark, chemical and other processing methods that exclude additional finishing manually are also widely used.

However, when performing metalwork, repair work, as well as during final processing of parts obtained by stamping, it is necessary to perform these works manually.

The use of special tools and devices to improve the performance of sawing and fitting. Such tools and devices include manual files with interchangeable blades and files from wire covered with diamond chips, filing prisms, filing basting, etc.

Fig. 2. Fitting: a - marking, b - fitting, c - filing, d - liner check

Fig. 3. Fit the oblique inserts: a - layout of the outer corners, b - sawing the outer surface, c - layout of the marking of inner corners, d - sawing the inner corners, e - check with the liner

Fit. To fit one part to another, it is first of all necessary that one of the parts be completely finished; on it and is fit. The file fit operation is one of the most difficult in the work of a mechanic. Performing this operation must show a lot of patience and perseverance.

In moving parts, the most significant obstacle is sharp edges and corners of the sawn surfaces. They need to be carefully repaired until the fitting parts fit into one another freely, without pitching. If the connection to the lumen is not visible, they lead on the paint. Usually, on customized surfaces and without paint, traces of friction of one surface over another are distinguished. These traces, having the appearance of shiny spots, show that these places interfere with the movement of one part over the other. Brilliant places (or traces of paint) must be removed with a file until the part is completely finished.

When any fitting work can not leave sharp edges and burrs on the details; they need to be smoothed with a personal file. How well the edge is smoothed can be determined by tracing it with your finger.

Rib smoothing cannot be mixed with chamfering. When chamfering on the edge of the parts do a small flat ribbon, inclined at an angle of 45 ° to the side edges of the part.

Fitting. The final fit of the parts — the point of Vyuya, without gaps, pitching and tilting — is called a fit. Templates, counterpatterns, die tools (punches and dies) and various other products are fit. In the template and countermount, the working parts must be very precisely stocked - so that when the matched sides of the template and countermount come in contact, there is no gap between these sides for any of the possible reciprocal rearrangements of the template and countermount.

The fitting can be performed when processing semi-closed and closed circuits. Both those and others are called proimy. The correctness of their contours is checked by small gauge-templates, which are made by the mechanics themselves. Such small testing tools are called workings. Consider the production of armholes on practical examples. Suppose you want to make a semicircular liner and armhole of 3 mm thick sheet steel.

Fig. 1. Seams: a - semi-closed loop: 1 - template (armhole), 2 - counter pattern (insert); b - closed loop: 3 - hexagonal arch, 4 - trihedral armhole; biquadratic armhole, liner and production

This work is done like this:

1. Cut the workpiece, each with a size of 82 X 45 X 3 mm.
  2. Outline the order of processing. It should start with an armhole, as it is easier to process and easier to measure with a measuring instrument.
  3. When making a part with an armhole, first clean and accurately saw off the wide surface and one narrow side 1 taken as the base. Then mark the armhole and the other three sides, cut out the armhole with a hacksaw and precisely cut the second side 3 parallel to the side and roughly cut the sides 2 a 4. Then proceed to sawing a semicircle 5 with a semicircular file, and during processing it is checked with a circular caliber of 40 mm in diameter, and the position center check with a caliper (from surface 3). Caliper readings when measuring a finished semi-circle should be equal to the height of the template plus the radius value.
  4. Next, make the second part-liner (counter pattern). First, a wide surface is treated, then three sides 6, 7 and 11; having done this, they mark sides 8 and 10 and the semicircle of the insert 9, cut a semicircular projection with a hacksaw, and proceed to filing sides 8 and 10; while ensuring that these parties were parallel to the base side 6 and lay in the same plane. Then cut a semicircular protrusion with a diameter of slightly more than 40 mm to an accuracy of 0.1 mm.
  5. When all of the above is done, proceed to fitting the liner at the armhole. The accuracy of the final fitting should be such that the liner enters the armhole without lumen, pitching and misalignment at any of the two possible edging at 180 °.
  6. After finishing the fitting, final finishing of the external surfaces is carried out.

Fig. 2. Fitting the armhole and liner

Consider the manufacture of a template with a hexagonal armhole and liner to it. Dimensions of the template 80X80X4 mm, liner 44 X 50 X 4 mm.

This work is done like this:
  1. First of all cut blanks.
  2. Work begins with the manufacture of liner; to him fit and fit in the armhole of the template. First, a wide surface is filleted as a base for processing the sides. Then the hexagon is laid out and sawn along the markings of its side, observing strict parallelism between each two opposite sides. The filing is carried out using flat-parallel basting with a rail screwed at an angle of 120 °.
3. Make a template with a hexagonal armhole, starting its processing with filing a wide surface of the workpiece. After that, saw the sides, then mark the circumference of the hole and hex. The hole diameter should be 1-2 mm smaller than the liner between its parallel sides.
  4. Starting the filing of the armhole, saws in the corners of a triangular file roll two parallel sides, behind them are the neighboring sides with checking the angles of the workings, and the parallelism of opposite sides - a caliper. Dimensions sawn hexagonal holes should be 0.05-0.08 mm smaller than the liner size. This allowance is removed in the process of fitting.
  5. Begin the fitting of the hexagon armhole on the liner, workings and calipers. It is conducted on parallel sides of the hexagon in the size of the liner, with verification of neighboring sides in the workings. An armhole is considered to be finalized and accurate if the liner is tilted in a hexagonal hole through each face in one or the other direction without distortions, pitching and gaps.

Fig. 3. The fitting of the hexagonal armhole on the liner and making

Fitting means mutual fitting of two parts that mate without a gap. Both closed and semi-closed circuits are fitted. The fit is characterized by high processing accuracy. Of the two parts to be fitted, it is accepted to call the hole an armhole, and the part entering the armhole is an insert.

In the manufacture and fitting of templates with a semicircular outer and inner contour, first produce a part with an inner contour - armhole (Fig. 151, d). To the treated armhole fit the liner.

Processing armholes are in the following order. At first, broad planes are precisely sawn off as base surfaces, then in rough outline — edges 1; 2; 3 and 4, after which the semicircle is marked with a compass, cut out with a hacksaw (as shown by the dotted line in the figure); produce an exact filing of a semicircular recess and check the accuracy of processing on a template, as well as on symmetry with respect to the axis using calipers.

When processing the liner, they first saw wide surfaces, and then the ribs 1, 2 and 3. Next, cut corners and cut with a hacksaw. After that, an exact filing and fitting of the fins 5 to 6 are performed. Then, an exact filing and fitting of the liner to the armhole are performed. The accuracy of fitting is considered sufficient if the liner enters the armhole without bias, pitching and gaps.

In the manufacture and fitting of oblique inserts and armored dovetail, shown in Fig. 151, d, first process the liner (processing and checking it easier).

The liner is processed in the following order. At first, wide planes are precisely sawn off as base surfaces, then all four narrow edges 1, 2, 3 and 4. Next, mark the sharp corners, cut them with a hacksaw and accurately cut them. First, edges 5 and b are sawed in a plane parallel to edge 7, then edges 7 and 8 along a ruler and at an angle of 60 ° to edge 4. The sharp angle (60 °) is measured with an angular pattern.

Next is the markup, cutting the groove with a hacksaw (shown in the figure by the dotted line) and filing the edges 5; 6 and 7. First, the groove width is made less than the required one by 0.05-0.1 mm while maintaining the strict symmetry of the side edges of the groove with respect to the armhole axis, the depth of the groove is immediately accurate in size. Then, when fitting the liner and the armhole, the groove width gets the exact size according to the shape of the protrusion of the liner. The accuracy of fitting is considered sufficient if the liner enters the armhole tightly by hand, without gaps, pitching and warps.

The filing prism (fig. 152, a) consists of two plates 1 with guides 2 and 3. The side surface of the plate has threaded holes 7 for fastening the clamping bar 4, rectangle 5 and ruler 6 with a bolt. The blank of all four narrow edges 1, 2, 3 and 4. Next, mark the sharp corners, cut them with a hacksaw and accurately saw off. First, edges 5 and b are sawed in a plane parallel to edge 7, then edges 7 and 8 along a ruler and at an angle of 60 ° to edge 4. The sharp angle (60 °) is measured with an angular pattern.

Fig. 152. Filling prism (a), filing reception (b)

The cross-section is processed in the following order. First, wide planes are precisely sawn off, after which all four edges are filed.

Next is the marking, cutting the groove with a hacksaw (shown in the figure by a dotted line) and filing the edges 5; 6 and 7. First, the groove width is made less than the required one by 0.05-0.1 mm while maintaining the strict symmetry of the side edges of the groove with respect to the armhole axis, the depth of the groove is immediately accurate in size. Then, when fitting the liner and the armhole, the groove width gets the exact size according to the shape of the protrusion of the liner. The accuracy of fitting is considered sufficient if the liner enters the armhole tightly by hand, without gaps, pitching and warps.

The use of special tools and devices to improve the performance of sawing and fitting. Such tools and devices include manual files with interchangeable plates and files from wire covered with diamond chips, filing prisms, filing marks, etc.

The manual file with replaceable plates has a body made of light alloy, in which replaceable inserts of high-quality carbon steel are firmly fixed. Plates have notches. Under each tooth there is a hole through which the removed chips are pressed, which prevents the teeth from clogging with chips.

This file is used to process steel, aluminum, copper, as well as wood, leather, rubber and other materials. After wear, the plates are changed. Experience has shown that prefab files are much more productive than normal ones

The filing prism (fig. 152, a) consists of two plates 1 with guides 2 and 3. The side surface of the plate has threaded holes 7 for fastening the clamping bar 4, rectangle 5 and ruler 6 with a bolt. The blank is placed between guides 2 and 3 so that a layer of metal to be removed, protruded above the planes of the guides, and firmly fix the clamping plate 4. The prism is fixed in a metal vice (Fig. 152, b). Squares 5 and ruler 6 are used to verify the installation of the workpiece.

The sliding frame is a type of filler prism and has the same purpose. It consists of two metal rectangular bars with grooves along the edges, which include two guide rails connecting these bars.

The rectangular block is tightly connected with screws to one end of the guide rails. Such a device allows installation in the sliding frame of blanks of different sizes (within the length of the guide rails).

The frame is installed in a metalwork vice, after which the workpiece is clamped in it, which is then sawn.

Questions for self-test

1. What are the features, techniques and rules of fitting?
2. How does sawing and fitting of three-sided holes occur?
3. What devices are used for sawing and fitting?