Isstari any art product from metal it was decorated with a protective film, and the craftsmen took into account the purpose of the object and the material from which it was made. Perhaps one of the old Kasli craftsmen drew attention to the black-brown coating formed from burnt oil and fat on the walls of cast-iron utensils. Where there was such a film, the dishes did not rust. Then the film began to be deliberately applied to sculpture and other artistic cast iron castings. A durable coating reliably protected the metal from rust and made the work more beautiful, more original.
Craftsmen working with non-ferrous metals are even more inventive. Using simple chemical and heat treatment, they learned to get almost any color on the metal surface. The chemical method of patination - this is the name of this type of finish - makes it possible to obtain a beautiful and durable film on copper, bronze, brass, steel.
Before you start patinating, understand well and strictly observe the precautions in the future. Many chemicals can be poisonous, so keep them in glass vials with well-ground stoppers, away from fire and food products. Keep sulfur separate from other chemicals - its vapors are explosive. Chemical processing of metal can only be done in a fume hood or outdoors in summer. Be sure to wear goggles over your eyes and rubber gloves on your hands. For the preparation of solutions and for the patination process itself, use porcelain, glass or plastic dishes. The plastic cuvettes used in photography are very convenient. When mixing acids with water or other liquids, remember that acid must be poured in small portions into water or into a solution, but not vice versa! If acid comes into contact with the skin, flush the area with tap water and then dampen with a 5% solution of baking soda.
Before moving on to various recipes for patinating solutions, let's talk about the sequence of patination.
Whatever way the metal is patinated, it is pre-cleaned, polished, degreased and bleached. Remove grease with a rag soaked in gasoline or alcohol, and bleach in a ten percent solution of some acid. Metal brightens very quickly. Rinse bleached metal with clean water. Dry the metal in the air or in sawdust from deciduous trees.
Now about the patination process itself. Immerse a small product in the solution as a whole, and patinate a larger one with a brush or a swab mounted on a wooden handle. Many solutions are opaque, so the product lowered into them must be removed and inspected from time to time. When you have achieved the desired color, rinse in clean water and dry.
Some films adhere to the metal rather weakly, while others appear whitish. To fix the film and remove plaque, the product after drying is wiped with natural drying oil, machine or vegetable oil. To visually enhance the relief of a patinated chased work, wipe it with a damp cloth with a fine powder abrasive (for example, ground pumice) or sand the protruding parts of the relief with GOI paste applied to felt or felt soaked in gasoline. The convex parts of the coinage are highlighted, and the natural color of the metal is exposed at the highest points. You need to wipe the coinage very carefully, achieving a smooth transition from the lightest area to the darkest. Wipe the washed and dried chasing with oil or cover with a thin layer of transparent varnish.
In order not to work blindly, but to know in advance what approximate color will turn out on the metal when processed with various solutions, prepare a reference table. Cut out identical rectangles from sheet steel, copper, brass and aluminum. Process them in the solutions, the recipes of which are given in this article. Fix the dried and oiled metal rectangles on a cardboard or wooden tablet, placing steel plates in one row, brass in the other, copper in the third, and aluminum in the fourth. Under each plate, make an inscription in which you indicate the solution used to tint the metal and the processing conditions. While working on the reference table, you will at the same time familiarize yourself with the rules for compiling patinating solutions, as well as learn other methods of decorative metal processing.
PATINATED BRASS
Brown and black colors. Make a solution of 1 liter of water and 60 g of sodium sulfite, which is often called sodium thiosulfite, or hyposulfite. In everyday life, hyposulfite is known as a fixer for photographic paper and film. Add about 5 g of acid (nitric, sulfuric or hydrochloric) to the solution. Immediately there will be a violent reaction with the release of sulfur dioxide. The solution will acquire a cloudy milky color. Dip a brass product into it and after a few seconds remove and inspect. The patina forms very quickly. If the desired color is achieved, rinse the product and dry. The solution has a patinating power for about 20 minutes, then it becomes unusable. True, an aqueous solution of hyposulfite can be stored for a long time, but only if acid is not added to it.
Do not overexpose the metal in solution. Not experienced craftsmen, wanting to achieve a more intense black color, keep the product in solution until a thick black coating forms. This patina is very weak and is easily washed off with a stream of water. Achieving absolutely black color is also not worth it because the natural luster of the metal is lost under a thick film. Whatever color the patina has, the metal should still be slightly translucent from under it.
If, instead of strong acids, about one tablespoon of vinegar is added to the hyposulfite solution, the same reaction will occur with the release of sulfur dioxide, but it will be much slower. To get an almost black color, brass will have to be kept in solution for at least half an hour.
Wipe the plates washed with water after drying with oil.
Reference table of approximate colors obtained on the surface of metals when various ways processing.
On the steel surface:
1 - hyposulfite with lead acetate (blue);
2 - ferric chloride with ferrous sulfate and nitric acid (black-brown);
3 - potassium dichromate (black-blue);
4 - hardening with cooling in oil (black).
On the surface of copper:
5 - sulfuric liver (black);
6 - sulfuric liver with sodium chloride (gray);
7, 8 - copper sulphate with zinc chloride (red-brown).
On the surface of brass:
9 - hyposulfite with acids (black and brown);
10 - chlorine-copper oxide with ammonia (olive, brown, black);
11 - potassium sulfide (orange-red);
12 - sulfuric liver (black and gray).
On the surface of aluminum:
13 - pigments (any color);
14 - smoked (black);
15-natural drying oil with calcination (brown);
16 - turpentine with calcination (olive).
Olive, brown and black colors. Make a solution of four parts of ammonia, five parts of water and two parts of copper oxychloride. Copper oxychloride and ammonia vapor are poisonous, so follow the safety rules that we talked about. Stir the solution with a glass rod.
It will take on a deep dark blue color. A brass object dropped into it quickly turns olive, then dark brown and black. After removing the object from the solution at the desired stage, rinse it with water and wipe it with a dry cloth. The patina is so strong that it can only be erased with abrasive materials. It should not be wiped with oil - the film already has a beautiful metallic sheen.
Orange-red color. Dissolve 5 g of potassium sulfide (potassium sulfite) in a liter of water. A brass object dipped into the solution will become covered with an orange-red bloom in a few minutes. After washing, wipe the metal with oil.
Gray and black colors. A strong and beautiful patina is formed on the surface of brass and copper treated in an aqueous solution of sulfuric liver.
To prepare sulfur liver, you need to mix one part of powdered sulfur with two parts of potash in a tin and put on fire. After a few minutes, the powder will melt, darken and begin to sinter, gradually acquiring a dark brown color. (By the way, the sintering of the patinated mass gave the name "liver" in the old days - from the word "oven", "sinter".)
During sintering, sulfur vapor can ignite with a weak blue-green flame. Do not knock down the flame - it will not degrade the quality of sulfuric liver. Stop sintering after about 15 minutes. For long-term storage, crush sulfur liver into powder and pour into a glass jar with a tight lid. When preparing a solution, add 10-20 g of sulfuric liver powder to one liter of water. The patina obtained on metal in a sulfuric liver solution is strong and beautiful.
COPPER PATINATION
Black and gray colors. Copper, like brass, is well patinated in an aqueous solution of sulfuric liver, acquiring a thick black color. But such intense coloring is not always necessary. Sometimes, to give an antique look to a copper product, it is enough to apply a light gray tint. In a liter of water, pour 2-3 g of sulfuric liver and 2-3 g table salt. After the appearance of a gray color, wipe the product and dry it.
Red-brown color. An aqueous solution of zinc chloride and copper sulphate stains copper red-brown. Mix one part copper sulphate with one part zinc chloride and dilute in two parts water. It only takes a few minutes for the copper to turn red-brown. After washing and drying, wipe the metal surface with oil.
STEEL DECORATION
Blue colour. It is easy to paint steel blue in an aqueous solution of hyposulfite and lead acetate. For one liter of water, you need to take 150 g of hyposulfite and 40-50 g of lead acetate. Steel immersed in the solution slowly turns a muted blue color. But if the solution is heated to a boil, the coloring will accelerate. After washing and drying, wipe the metal with oil.
Blueing. Of the many well-known recipes for bluing steel, we offer you the simplest, but giving beautiful and durable coatings. In a liter of water, dilute 15 g of ferric chloride, 30 g of ferrous sulfate and 10 g of nitric acid in succession. When you lower the product into the solution, a rusty coating will appear on the metal. Remove it with a brush and lower the product into the solution again. After a while, a rusty coating will appear on the metal again, which must also be removed. If the burnishing process is carried out correctly, the brown color on the surface of the steel will become thicker. And to get a thick black-brown, almost black color, this process must be repeated several times. After washing and drying, rub the steel with oil.
Tempering colors on steel due to different temperature heating.
Burnishing and black-blue color. Most often, bluing is understood as obtaining black steel with a slight bluish tint, like a raven's wing. To get this color, dilute in a liter of water 100 g of potassium dichromate, more commonly known as chromic in everyday life. After lowering the product into the solution, hold it there for twenty minutes. After removing from the solution, dry at a high temperature, for example, over an electric stove or over hot coals. The metal will acquire a gray-brown color. Repeat the same operation several times until a deep black color with a bluish tint is achieved. The metal must be wiped with oil.
Temper colors. In addition to chemical, there is another fairly simple way to decorate steel - thermal. (By the way, different colors can be obtained on copper and brass in the same way.) If you heat the metal in a muffle furnace or gas burner, the tint colors on it will quickly begin to change sequentially - from straw yellow to blue-black. The metal is abruptly stopped heating at the moment when the desired color is obtained on it. By heating the chased work with a gas burner or a blowtorch, moving the flame at your discretion, you can achieve different colors of individual sections, a smooth transition from one color to another.
Burnishing with hardening. Heat a metal object red-hot and dip it in machine oil. It will immediately take on a deep black color. So you can decorate small items, for example, decorative chains of pendants.
ALUMINUM DECORATION
Aluminum has many advantages, thanks to which it is readily used by craftsmen. decorative arts. It is light, soft, plastic, has a beautiful silvery color. But aluminum is almost not amenable to chemical patination. The current chemical patination methods require sophisticated equipment. Therefore, tinting, smoking and roasting are often used instead.
Patination with pigments. The easiest way is patination with oil paints. With a piece of cloth, apply a thin layer of paint to the metal, making sure that all areas are completely processed. Then wipe the product with a dry cloth. In raised areas of the relief, the paint is removed more than in the depressions, creating the illusion of a higher relief. The advantages of this patination method are that it is completely safe, and besides, you can create any color of the patina by mixing paints on the palette. It should be noted that only aluminum can be successfully patinated in this way. Instead of oil paint, you can take black ink, graphite powder, black bituminous varnish.
Black and gray colors. Wipe the relief or sculpture with a thin layer of natural drying oil or some vegetable oil. Place the metal over the smoky flame. Smoke small things over a candle, and larger ones over a bunch of candles or over a burning birch bark placed in a tin can. It is convenient to smoke especially large products with the smoke of a torch moistened with kerosene. The smallest particles of soot eat into the drying oil, firmly adhering to the metal surface. To make it convenient to monitor how the soot falls on the metal, the product should be above eye level. You can smoke the metal evenly, but you can achieve an interesting decorative effect, then reducing, then increasing the layer of soot. After applying the soot, place the product over coals or in a muffle furnace. Make sure that the film is well calcined, and not burned out. The disappearance of gloss on any part of the product is a signal that indicates the beginning of the film burnout. During smoking and hardening, observe fire safety rules.
Golden yellow and brown colors. Various shades from golden yellow to dark brown and even black can be obtained by calcining an aluminum product coated with a thin layer of turpentine, drying oil or vegetable oil. Place the product rubbed with oil over a fire or over hot coals. The flame must not touch the surface of the product. To get a uniform color, rotate the product evenly over the fire. When the metal surface acquires the desired color, allow the product to gradually cool.
Aluminum coated with turpentine, after calcination, acquires a golden brown color, and drying oil - red-brown and black. These methods can also be used to decorate cast iron, steel and other metals.
When decorating any metal, always keep in mind that you should not apply too thick a layer of decorative film. The material must always be felt, its natural beauty and characteristic brilliance. Very carefully, you need to use bright open colors, which can variegate the product, violate the integrity of its perception.
In conclusion, we once again remind you of the need to strictly observe the safety rules described at the beginning of the article.
§ 14. FINISHING PRODUCTS WITH PAINTING
1. What is the essence of technological operations performed during the finishing of products?
2. What methods of finishing products do you know?
3. What is the purpose of finishing products?
4. What is the technology for finishing wood products using a stencil?
For more reliable protection of metal surfaces from corrosion and to give them an attractive appearance, they are painted or varnished. Such technological operations are carried out after performing anti-corrosion treatment, that is, removing rust, dust, dirt, scale, and surface primer from the metal surface.
The essence of the primer is to apply a special solution-primer to the surface of the product, which serves for better adhesion of paints and varnishes. The industry produces different types of primers for this (Fig. 160).
If the surface has scratches or dents, it is puttied, that is, it is filled with a special plastic putty paste. To do this, use ready-made putty paste (Fig. 161). The industry produces its various types: for puttying metal, wood, plaster, etc. The most common is the universal putty used for puttying the surfaces of all of the listed materials. Before purchasing this material, you must familiarize yourself with the purpose and technology of its application to the surface, which is indicated in the instructions on the package. Puttying is carried out with a special rubber or metal tool - a spatula (Fig. 162).
Putty is applied with a spatula in a thin layer, first along and then across the surface (Fig. 163).
Rice. 160. Soil mixtures
Rice. 161. Putties
Rice. 162. Types of spatulas: a - rubber; b - metal
Rice. 163. Puttying techniques
Rice. 164. Mixtures for decorative coating: a - varnish; b - paint
In this case, the spatula is placed at an angle of approximately 60 ° to the surface and make sure that there are no traces of the tool on it. Small irregularities are removed with a fine-grained sandpaper after the putty has completely dried.
The last stage in the processing of metal products is decorative processing, that is, painting or varnishing. The type of final processing and the choice of paint or varnish color are determined depending on the purpose of the part or product. The industry produces many types of paints and varnishes (Fig. 164). Therefore, when purchasing them, it is necessary to read the instructions on the package, and before use, thoroughly stir the material until a homogeneous mass is formed.
Paints and varnishes are applied using various tools. For staining, flutes, rollers and brushes of appropriate sizes are used (Fig. 165). When using painting tools, it is necessary to ensure that when dipping them into the paint, there is not too much of it on the working part. To do this, the flute or brush is dipped in about a third of the working part, and after dipping, the roller is shaded by moving it back and forth in the bath so that the paint evenly seeps around its entire perimeter (Fig. 166).
Rice. 165. Tools for coloring: a - flutes; b - roller; c - brushes
Rice. 166. Preparation of tools for applying paint: a - with a flute; b - roller
Rice. 167. Coloring gloves
Staining must be done with special rubber gloves (Fig. 167). After completion of work, they are wiped with swabs to remove paint residues and stored for further work.
Since metal surfaces do not seep through with paint mixtures, drops and traces of leaking paint (streaks) can form on them. After they dry, irregularities are formed that worsen the aesthetic appearance of the product. To prevent this, you need to use thick paint, and it must be applied in a thin layer, carefully rubbing (shading) along and across the surface or up and down, and then to the right and left with a vertically placed workpiece. Methods for applying paint mixtures are shown in Figure 168.
After applying the first layer of paints and varnishes and drying them, a second layer is applied. To give the product the best appearance, the second layer after it dries polished. After staining, the instruments must be prepared for storage. To do this, they must be thoroughly cleaned of paint or primer residues. For this purpose, they are squeezed and wiped, then washed with drying oil and stored on special stands in vessels with water (Fig. 169).
Rice. 168. Methods for applying paint mixtures: a - with a flute; b - roller
Rice. 169. Storage of brushes: a - on a suspension; b - in clamps
Rice. 170. Paint sprayer
Rice. 171. Drawing a picture using a stencil
At present, the use of electromechanical hand tools - sprayers of paint mixtures - spray guns has become widespread. In them, the paint is applied to the surface under the action of compressed air (Fig. 170). You will learn about the features of working with this tool later in the lessons of labor training.
Finishing can be done by applying a pattern to the metal surface using a stencil. To do this, it is fixed on the painted dry surface of the workpiece and a thin layer of paint is applied with a swab or brush, while making sure that stains do not form under the stencil (the amount of paint mixture on the swab or brush should be minimal). After the paint has dried, the stencil is carefully removed (Fig. 171).
While doing finishing works the following safety rules must be observed:
1. Do not put unnecessary materials and tools on the table.
2. Monitor your working posture, maintaining the correct posture.
3. Work with dyes and solvents very carefully, avoiding their contact with open parts of the body, especially take care of the face and eyes.
4. Paint mixtures can be applied in specially designated areas equipped with ventilation.
5. Only oil-based paints and varnishes are used in school workshops.
7. When painting or varnishing products, you need to constantly ventilate the room.
8. Before varnishing, it is advisable to lubricate your hands with petroleum jelly, and after work, wipe them dry with a clean cloth.
9. In case of contact with the skin, wash your hands with soap and water; if the varnish is not washed off, moisten it with ammonia.
10. Handle products with abrasive skins carefully so that parts of the abrasive substances do not get into the eyes.
PRACTICAL WORK №15
Painting of metal surfaces
Equipment and materials: oil paint, drying oil, paint brushes, brushes, glass size 60 x 60 cm, metal brush, sanding paper, polishing paste, felt, sanding, cleaning cloth.
It is carried out in the presence of exhaust equipment!
Work sequence
Preparation of oil paint for work.
Determination of approximate paint density
1. Carefully read the instructions on the paint package.
2. Open the package. Stir the paint until smooth.
3. To check the thickness of the paint, put a drop of it on a piece of clean, dry glass.
4. Put the glass vertically, let the paint drain. The thickness of the paint is considered suitable for use if the length of the paint drip on the glass is 35...50 mm. If the length of the drip is less, dilute the paint with drying oil, if it is longer, add thick paint.
Applying oil paint to metal surfaces
1. Prepare for dyeing products made in previous lessons.
2. Clean the surface of rust.
3. Perform grinding and polishing of the surface, if these technological operations were not performed with respect to the selected object of labor in the previous lesson.
4. Clean the surface of dirt.
5. Apply a coat of paint to the surface.
6. After the first layer has dried, apply the second layer.
7. After the paint has dried again, remove the unevenness with a sandpaper, clean the dirt with a damp cloth, and dry the product.
8. Polish the product.
9. Apply the third coat of paint.
10. To give the painted surface greater strength and shine, after thoroughly drying the painted surface, cover it with oil varnish.
Coloring, paints and varnishes, shading, airbrush.
Brush - a bundle of even bristles, hairs attached to the handle, which is used to apply paint, glue, varnish.
Airbrush - an apparatus for mechanical spraying of non-viscous mixtures of paints.
Shading - the application of a thin layer of paint or varnish by thorough rubbing.
Solid oil is a thick oil that covers metal surfaces.
Fleitz - a flat wide brush (brush) made of soft hair, which smoothes a freshly painted surface.
Nozzle - a device with which the paint mixture is sprayed.
1. What technological operations are called finishing?
2. What are the features of painting metal surfaces?
3. What preparatory technological operations precede staining? varnishing?
Test tasks
1. The process of giving the product an aesthetic appearance is called ...
And decoration
Used varnishing
In finishing
D all answers are correct
D no correct answer
2. A film that protects products from thin sheet metal and wires from influence external environment, is formed as a result of ...
A grinding
B varnishing
In filing
G-burn-in
D painting with oil paints
3. The process of giving the product a beautiful appearance by staining and varnishing is called...
And decoration
Used trim
In hand-painted
Product Finishing The finishing of sheet metal and wire products in the training workshop includes edge deburring, part sanding and painting. These operations give the product a beautiful appearance and increase its resistance to wear and corrosion. For this purpose, products made of thin sheet metal and wire are cleaned with a file and sandpaper and coated with paint or varnish. The edges are cleaned with a fine-grained file. With it, remove burrs, dull sharp corners. Small irregularities, scratches are removed with a sandpaper. For the convenience of cleaning the edges of sheet metal blanks, it is recommended to fix them between two wooden planks in a vise. Thin and short parts are processed on a sheet of sandpaper. The parts are pressed with a wooden block and, with some effort, are moved back and forth along the surface of the skin. Before painting or varnishing the surface, the parts are degreased with special solutions (as directed by the teacher) or wiped with a cotton swab dipped in a soda solution. Paint or varnish is applied to a dry surface by spraying from cans or with a brush evenly over the entire surface (see figure on the right). The oil paint applied with a brush is carefully rubbed in all directions. Enamel paint (enamel) is applied without rubbing. The second layer of paint or varnish is applied after the first has dried. In this case, the paint layer becomes even, and the painted surface takes on a beautiful appearance. Coating with paint or varnish protects the surface of products from corrosion. Brushes are stored in a glass jar with water or in a special suspension. The coating of surfaces of metal products with oxide films is widely used - oxidation. For this purpose, the product is heated in a muffle furnace and cooled in a special solution (prepared by the teacher). The surface of such products has a black or dark blue color. This finishing method is called bluing (blackening). Fast blackening (similar to bluing and oxidation) is the process of imparting a beautiful, uniform black decorative and protective coating to metal products at room temperature. At enterprises, anticorrosion finishing of metal products is carried out by tinkers (tin coating), electroplating (electrolytic coating with chromium, nickel, etc.), metallizers (coating with any sprayed metal). Workers in these specialties must have a good knowledge of the properties of metals and alloys and the arrangement of installations for finishing products. Carry out painting and varnishing work in a ventilated area. Keep hands and clothes clean. Do not touch eyes and face with dirty hands. Do not paint products near heating devices. Wash hands thoroughly with soap after finishing work. Sheet metal and wire Metals are widely used in national economy. They are durable, conduct heat well, electricity , have a special metallic luster. Machine tools, machines, various building structures, many household products are made from metals. Metals are usually used in industry not in pure form, but in the form of alloys. The most important metal alloys include steel and cast iron (iron-carbon alloys), bronze (copper-tin alloy), brass (copper-zinc alloy), duralumin (aluminum alloy with copper, manganese, magnesium, etc.). Metal alloys are produced in the form of sheets, angles, bars of various sections, wire, etc. In the school workshop, they work mainly with thin sheet metal and wire. Such metal is obtained by rolling an ingot on special machines - rolling mills (see the figure on the right). In the figure, the numbers indicate: 1 - blank; 2 - rolls; 3 - rollers. Hot metal is passed between rotating rolls, they compress the ingot and give it the shape of a sheet. Sheets are rolled up. Sheet steel can be of several types: tin - sheet thickness 0.2-0.5 mm, roofing steel - 0.5-0.8 mm, etc. There are black and white tin. Black tin is named because the color of the surface of the sheet after rolling is black. The white plate is covered with a thin layer of tin. This protects it from corrosion (rust). Roofing steel is black or covered with a thin layer of zinc (galvanized steel) or oil paint. Sheet steel is used to make cases of instruments, machines, drainpipes, dishes, cans, etc. Work related to the processing of sheet metal is performed by tinsmiths. They must know the properties of metals and alloys, the design of various machine tools and devices, and have the skills to work with various tools. Wire with a thickness of more than 5 mm (rolled wire) is obtained by rolling hot metal on special mills. Thinner wire is made on drawing mills. There, the wire rod is sequentially pulled through holes of various diameters. A diagram of this process is shown in the figure on the left. They produce steel, copper and aluminum wire. Nails, screws, screws, rivets, springs and other products are made from steel wire. Copper and aluminum wire is mainly used for making electrical wires. Every third ton of steel is produced from scrap metal. It costs 25 times less than the smelting of steel from pig iron. Graphic representation of parts made of thin sheet metal and wire Parts made of thin sheet metal and wire are depicted in the form of a technical drawing, drawing, sketch. Drawings of several products are shown in the figures below. The diameter of the hole, ring is indicated by the sign Ø (see figure on the right). The number next to this sign indicates the diameter of the hole in millimeters. If there are several holes of the same diameter nearby, then in the drawing, above the extension line (starting at one of the holes), the number of holes and their diameter are written. The thickness of the sheet metal part in the drawing is denoted by the letter S, and the number immediately following the letter is the thickness of the part in millimeters. The radius is denoted by the sign R, next to it is put down a number indicating the size of the radius. If the wire diameter is less than 2 mm, then it is depicted in the drawing as a solid thick main line (see the figure on the left). A wire with a diameter of more than 2 mm is shown by two parallel solid thick main lines with an axial dash-dotted line in the middle (see figure on the right). The fold lines in the drawing (sketch) must be shown with a dash-dotted line with two points, the centers of circles, holes - with dash-dotted (center lines) intersecting at right angles. The center dash-dotted lines must intersect the contour lines. When calculating the length of a piece of wire, remember that the circumference is 6.28R. Process of making thin sheet metal products Various sheet metal and wire products are made in the training workshop. Products may consist of one or more parts. Their manufacture includes operations: straightening, marking, cutting (with scissors, wire cutters), drilling, bending, cleaning and finishing. Most often, sheet metal products are obtained by bending flat (from wire - straight) blanks. Marked sheet or wire blanks are called reamers (see figure on the right). In order to unfold any part, its dimensions and the required material are determined from the sketch, and then a workpiece is selected. The workpiece must have a processing allowance. We must strive to ensure that the allowance was as small as possible. After all, when processing a part, the allowance metal turns into waste in the form of chips or sawdust. The selected workpiece is straightened, marked, cut, bent, connected with rivets or bolts, and then the product is finished. The construction of a drawing (sketch) of a product development should begin with an image of its base. After that, other sides are drawn adjacent to the base along the fold lines. The development of a cylindrical product is a rectangle, one side of which is equal to the height of the product, and the other is the circumference of its base. Marking When marking, marking lines (risks) are applied to the surface of thin sheet metal using marking tools and fixtures. The figure shows tools for marking sheet metal workpieces - a scriber (sharp-sharpened steel rod), a marking compasses. Marking can be done using a template - a flat sample part. The template is pressed against the surface of the workpiece (a clamp can be used for this deli) and the contours of the template are traced with a scriber, firmly pressing the tip of the scriber to the edge of the template. The marking of rectangular parts according to the drawing (sketch) begins with determining the base edge of the workpiece and applying the base risk. The smoothest edge of the workpiece is selected as the base for marking. Marking is carried out from it: the base risk is drawn along the ruler (Fig. a), the second risk is drawn along the square at an angle of 90 ° (Fig. 6), size A is laid along the ruler (Fig. c), the third risk is drawn along the square (Fig. d), set aside the size B (Fig. e) and draw the fourth risk along the square (Fig. f). The tip of the scriber should be firmly pressed against the ruler, and the ruler itself should be tilted in the direction of movement. Risk must be applied only once. The tip of the scriber is pressed against a ruler or template, but not placed vertically (see figure on the right). The figure below shows marking with a center punch and a marking compass. With a light blow of a hammer on the punch striker, the centers of arcs and circles are applied (punched) onto the workpiece. The leg of the marking compass is installed in these centers. When marking, the compasses are slightly tilted in the direction of movement, and the force is applied to the leg that is in the center of the circle. Before marking, it is necessary to clean the workpiece from dust, dirt, traces of corrosion and check the serviceability of the marking tools. Markup is a very responsible operation. The quality of the future product depends on how accurately it is performed. You can not draw a scriber on the same place more than once. The scriber must be handled very carefully so as not to injure the eyes or hands. It must be served with a handle away from you, and put on workplace- with a pen towards you. You can not put the scriber in the pocket of a dressing gown, you can only keep it on the table. In production, manual marking is used in the manufacture of templates, models, product samples. AT tool shops marking is carried out on special boring machines. Markers are employed at the marking enterprises. Templates are made by highly qualified toolmakers. Selection and editing of workpieces from sheet metal To choose the right workpiece, you must carefully study the drawing (sketch) of the part and determine the allowance for processing (see the figure on the right). Then the workpiece is straightened (surface leveled), if necessary. Editing is performed before marking and after cutting blanks. Sheet metal (steel, copper, aluminum) up to 0.5 mm thick is ruled by a wooden block - a trowel (see fig. a), which is moved over the surface of the workpiece. The workpiece must be placed on a smooth, hard surface. Sheets of metal with a thickness of more than 0.5 mm are ruled with a wooden hammer - a mallet (see Fig. b). Very thin sheet metal - foil - is ruled with a cotton swab. Editing of metal strips begins with the most protruding part of the strip. To control the editing of metal strips, the workpiece is held by hands at eye level. In factories, sheet metal is corrected on special sheet straightening mills. Sheets of metal are passed between rotating rolls. On the hand that holds the workpiece, you need to put on a mitten. Hands should be protected from cuts on the edge of the workpiece made of metal. When straightening blanks, blows must be applied from the edges of the sheet along the entire perimeter towards the convex part, otherwise the convexity may increase. Approaching a convex place, you should gradually reduce the force of the blow, but strike more often. Sheet metal bending Sheet metal bending is performed in a vise according to the level of the jaws or with the use of special devices - mandrels (see figure on the right). In order not to wrinkle the workpiece, overhead squares made of softer material are put on the vise jaws (see the figure on the left). Bending is performed with a wooden hammer (mallet) or a metalwork hammer, but at the same time, blows are applied not to the workpiece, but to a wooden block - it bends the metal without leaving dents on it. The workpiece is fixed so that the fold line (marking line) is at the level of the corners, vise jaws (fig. right) or mandrel rib (fig. right). With light blows of a mallet or a hammer, the edges of the workpiece are first bent, and then the entire intended part. For a large number of products that need to be bent in the same way, special templates (beds) are made of thick metal. A thin sheet metal plate is driven into the bed and it takes on the desired shape. When working, it is necessary to securely fix the workpiece with the mandrel in a vice. A mitten must be worn on the hand holding the workpiece. You can not stand behind the back of the worker. Bending of sheet metal in production is performed on bending machines. Such bending is called mechanical (see the figure on the right). The main part of bending machines is the die. It consists of a matrix and a punch. The shape of the working part of the matrix and the punch is the same and repeats the shape of the part. A sheet of metal is placed on the matrix. Under the action of the press, the punch enters the matrix and bends the sheet, giving it the desired shape. For parts of different shapes, you need your own stamp. The use of bending dies ensures high precision of products, dramatically increases labor productivity. Cutting thin sheet metal with shears Thin sheet metal can be cut with special shears. Hand scissors consist of two halves. Each half is made as a whole and combines a knife and a handle. The halves are screwed together. According to the location of the cutting knives, hand scissors are divided into left (Fig. left a) and right (Fig. left b). If you look at the scissors from the side of the knives, for the left scissors the upper knife is located on the left, for the right ones - on the right. According to the shape of the cutting knives, straight (Fig. Right a-d) and curved scissors (e) are distinguished. To reduce the effort required to cut a durable material, lever scissors are used (see the figure on the left). The cutting edges of the knives of the scissors must be well sharpened, and the cutting planes should fit snugly against each other and be well secured with a screw. The quality of sharpening scissors can be checked by how well or poorly they cut paper. Sheet metal can be cut in two ways. The first way - scissors are taken with the right hand. The thumb is placed on the upper handle, and the index, middle and ring fingers cover the lower handle. The little finger is placed between the handles: when cutting, they push the handles of the scissors apart (see the figure on the right). If the handles of the scissors move apart tightly, then instead of the little finger, you can use the index finger. In this case, it is placed between the handles of the scissors. The second way to cut sheet metal is that one handle of the scissors (the one on the bottom) is clamped in a vice, and the other is covered with the fingers of the right hand (see the figure on the left). The material in both cases is served with the left hand. This method allows you to significantly increase the pressure between the knives and cut harder material. The workpiece is slightly lifted and fed towards itself, and the blade is directed exactly at the risk. After cutting, the workpiece is straightened, burrs are removed from the edges, sharp corners are blunted, and the cutting quality is checked with a ruler and square. The techniques for cutting a sheet of metal with scissors in a straight line are somewhat different from the techniques for cutting along a circle or other curve, but in any case, it is necessary that the cut line is always visible during the cutting process. When cutting along a curved line (see the figure on the right), there are difficulties in moving the scissors, since in the place of rounding the cut off part of the metal bends worse and interferes with the work of the scissors. In order to avoid this when cutting, for example, a circle from a square sheet of tin, first cut off the corners along straight lines, and then cut out the circle, cutting off a narrow strip of tin (see the figure on the left). When working, the scissors should not be fully opened, but only enough so that they capture the sheet. If you open the scissors too wide, they will not cut, but push the sheet. When cutting thin sheet metal with scissors, the cut off part is strongly bent and the edges of the sheet at the cut point become very sharp. Therefore, on the left hand supporting the sheet, be sure to wear a mitten. The left hand should not be on the cutting line. When cutting a sheet along a long line, do not completely compress the knives, as this can lead to cracks and even breaks in the edges of the material at the cut line. The fastening of the scissors in the vise must be strong and reliable, since if they break, you can injure your hands on the jaws of the vise. Do not touch the cut edges of the workpiece with bare hands. Feed the scissors with the handles away from you, and put the other way around. At the enterprises, sheet metal is cut on special scissor machines. Distinguish mechanical scissors - guillotine and disk. There are two types of guillotine shears: parallel and inclined. In the former, the knives are parallel to each other, in the latter, at a slight angle. In a circular shear, the sheet metal is cut by the sharp edges of the rotating discs (see picture on the left). For curly cutting, nibblers are used, the upper knife of which rotates around the axis, and the lower one is stationary (see the figure on the right). Cutting blanks at the enterprise is performed by metal cutters. They must know well the properties of various metals and the design of industrial scissors, be able to mark workpieces. Recently, metal cutting with a laser beam, a jet of water under high pressure, has become widespread in production. These methods are characterized by high performance and accuracy. Punching and drilling holes. Holes in thin sheet metal can be obtained by punching or drilling. To punch holes with a diameter of up to 8 mm, a punch (beard) is used - a steel rod with a flat working surface (see fig. right a). A sheet of tin is placed on the end of a wooden block, a punch is installed at the desired point and a hole is punched by blows of a locksmith's hammer on the striker (see figure on the right b). The edges of the resulting hole on the underside of the sheet are aligned with blows from a mallet or hammer. In factories, to make holes in sheet metal, instead of a punch, a special tool is used - a punch. Holes are punched on a punching press (see figure on the left). A sheet or several sheets are placed on a matrix with one or more holes. A punch or several punches under pressure enter the matrix and punch holes, pushing out waste - circles with a diameter equal to the diameter of the holes. When punching holes, work with a serviceable hammer. Do not keep fingers near the working part of the punch. More precise holes in metal can be obtained by drilling. Drilling is called technological operation on the processing of materials by cutting with a drill. At the same time, the same techniques and rules for safe work are followed as when drilling holes in wood. The location of the hole is marked with a center punch so that the drill does not slip on the workpiece (see the figure on the right). There are different types of drills. The most common of them are spiral ones (see the figure on the left). During drilling, the cutting part of the drill cuts into the material of the product and removes the chips, which are then removed through the helical grooves located on the guide part. Ribbon allows you to reduce the friction of the drill on the walls of the hole. The shank with a foot serves to secure the drill during drilling. When drilling, the product is fixed motionless, and two movements are simultaneously reported to the drill: the cutting motion is rotational around the axis and the feed motion is translational along the axis of the drill. Tools and accessories for drilling. When drilling, it often becomes necessary to expand the upper part of the hole in order to deepen the head of a bolt, screw, screw, etc. into it. To do this, use a larger diameter drill or a special tool - a countersink (see figure on the right). The operation of processing the upper part of the hole with a countersink is called countersinking. To secure the workpiece during drilling, a machine vice is usually used (see the figure on the right). A fixed sponge is fixed on their base, and a movable sponge can move along the guide using a screw with a handle. The product is installed between the jaws and by turning the screw with the handle, the movable sponge is moved and the product is firmly fixed in a vice. If drilling is done on a drilling machine, then the vice itself can be fixed on the machine table. To do this, notches are made at the base of the vice, and there are special grooves on the machine table. Having installed bolts with a nut in the grooves of the table and the recesses of the vise base, the vise is fixed on the table of the drilling machine. Before installing a machine vise, thoroughly wipe the table support surfaces and vise bases and lightly lubricate them with machine oil. When drilling small diameter holes, it is not necessary to secure the vise. The device of the drilling machine and methods of work. A drilling machine, like any technological machine, consists of the following components: an engine, a transmission mechanism, a working body, and controls. The transmission mechanism serves to transfer movement from the electric motor to the working body, which is the drill. It is mounted in a chuck mounted on a rotating shaft - spindle. Rotation from the electric motor to the spindle is transmitted using a belt drive. By turning the feed handle, the drill chuck can be raised or lowered using a rack and pinion. On the front panel of the machine there are buttons for turning on and off the electric motor. Turn on the machine by pressing one of the extreme buttons, depending on the desired direction of rotation of the spindle. Turn off the machine by pressing the middle red button. A vertical screw-column is fixedly attached to the base of the machine. By turning the handle, you can move the headstock up and down along the screw-column, and fix it in the required position with the handle. A scale is provided to control the depth of blind holes. Depending on the workpiece material, different drilling speeds are required. To do this, set the required spindle speed by transferring the belt drive belt to pulleys of different diameters. Before drilling, remove all unnecessary items from the desktop of the machine. The workpiece with the punched centers of the holes is fixed in a vise. A drill of the required diameter is inserted into the chuck and secured with a special key. To check the correct installation of the drill, briefly turn on the machine (with the permission of the teacher). If the drill is installed correctly in the chuck, its tip does not describe a circle when rotated. If the drill is installed skewed and its runout is observed, then the machine is turned off and the drill is fixed correctly. Then, turning the feed handle, lower the drill and set the vise with the workpiece so that the core coincides with the tip of the drill. Turn on the machine and drill a hole, gently pressing the feed handle without jerks and great effort. When drilling through holes, the workpiece is placed on a wooden block so as not to break the drill and damage the machine table (see figure on the right). When drilling deep holes, it is necessary to take the drill out of the hole from time to time and cool it by dipping it in a container with coolant. At the end of drilling, the pressure on the feed handle must be reduced. Having drilled a hole, you need to smoothly turn the feed wheel, raise the spindle to its highest position and turn off the machine. Drilling can be done with a hand drill, an electric drill (see the figure on the left). When drilling thin sheet metal, a conventional twist drill crushes and tears the workpiece. In this case, drills with special sharpening are used (see the figure on the right). You can work on a drilling machine only with the permission of the teacher. When working on the machine, the dressing gown must be fastened with all buttons, the hair is removed under the headdress. Use protective goggles when drilling. Install the drill in the chuck and the workpiece in the vise, as well as remove the chips from the table, only after turning off the machine. It is impossible to slow down a rotating cartridge with your hands. Do not leave the machine without turning it off. Securely clamp the workpiece in a vise, the drill in the chuck and the chuck in the spindle. When drilling with an electric drill, do not press hard on the handle of the drill. The axis of rotation of the drill when working with a drill must be strictly perpendicular to the plane of the workpiece. At enterprises drilling machines operated by drillers. They must know the device of the machine, be able to set up and maintain it, choose the correct drilling speed, be able to use various drilling devices, sharpen tools, understand the drawings. In the workshops of factories, more complex machines are used than we have just considered. These are vertical drilling, radial drilling, multi-spindle machines and automatic machines that perform drilling operations without human intervention according to a given program. Connection of thin sheet metal parts. There are several ways to connect sheet metal parts. The simplest of them is a seam seam connection. It is obtained in the following way. At a distance of 6 ... 8 mm from the edge of the sheets to be joined, fold lines are marked and the sheets are bent at a right angle (see figure on the left a). Then the edges of the blanks are folded (see the figure on the left b), they are connected into a lock (see the figure on the left c) and the sheets are folded near the seam with a wooden block, as shown in figure d, so that the connection does not come apart. The connection of parts with a seam seam is used in the manufacture of buckets, drainpipes and ventilation pipes, tin cans, as well as when covering the roofs of houses with roofing steel. In factories, this work is done by tinsmiths on seam-rolling machines. Variants of such machines are shown below. In addition to seam seam joining, sheet metal parts can be joined using rivets. Rivets are used to create a so-called "one-piece" connection. Usually, thin metal sheets are connected with the help of rivets, facade plates are fastened, as well as rather heavy structures. Rivets have been used as fasteners since time immemorial. It is enough to visit any archaeological museum to see this with your own eyes. For example, ancient warriors wore armor, metal plates which were connected exclusively by rivets. And if you remember that rivets were used as the main (almost the only) fastener in the construction of the Eiffel Tower and the Aurora cruiser, you involuntarily imbued with respect for the people who invented fasteners so familiar today. Rivets are the fasteners consisting of a mortgage head and a core. They are made of mild steel, copper, aluminum, brass. There are rivets with semicircular (a), countersunk (b), flat (c), semi- countersunk (d) heads (see figure on the left). To connect parts with rivets, first mark the centers of the holes for the rivets. Then holes are punched with a punch or drilled. The dimensions of the rivets depend on the thickness of the parts to be joined. It is recommended to take the rivet diameter equal to twice the thickness of the thinner part. The length of the rivet rod consists of the thickness of the parts to be joined and the length of the protruding part (it is equal to 1.25-1.5 of the rivet diameter), on which the closing head is formed. Often, two workpieces to be joined are drilled at once, clamping them with a clamp or in a vice. The hole diameter D must be 0.1 ... 0.3 mm larger than the rivet diameter d (see figure on the right a). The rivet is inserted into the hole (fig. b), and the length of the protruding part of the rivet should be (1.3 ... 1.6) d. The insert head is placed in the support recess (2) (fig. c) and the parts to be joined are brought together by hammer blows on the tension (1). Then, with circular blows of the hammer (3), the protruding head is riveted (Fig. d) and given the correct shape by means of crimping (4) (Fig. e). When making a riveted connection, it is necessary to check the reliability of the hammer nozzle on the handle. The workpiece must be securely fixed in a vise. You can not stand behind the back of the worker. Rivet joints are used in aircraft construction, shipbuilding, for connecting parts of bridges, and in the manufacture of metal utensils. In industry, workpieces are riveted using pneumatic riveting hammers or special riveting machines. Undoubtedly, rivets have a lot of undeniable advantages. But standard, so-called "full-bodied" rivets also have a rather significant drawback - in order to create a truly reliable connection, great attention must be paid to the quality of work with them. Considering that the rivet must be held tightly on the other side during riveting, this is a rather laborious task. However, progress does not stand still. The development of riveting technology has led to the emergence of blind rivets that solve this problem. The setting tool (see figure on the left) for working with blind rivets is relatively inexpensive, and the convenience of their use is very high. Mechanical engineering, the construction industry, the automotive and furniture industries, and enterprises in the electronics manufacturing industry actively use the blind rivet, since the single-sided fastening technology is definitely more convenient and more reliable than other fastening methods. A single-sided pull (exhaust) rivet consists of two parts: a body and a rod. The body of the rivet is made from various materials : aluminum, steel, stainless steel, copper, MONEL alloy (Ni/Cu=70/30). The core of blind rivets is made of steel or stainless steel. Design features: the rivet has a convex or hidden head. Rivet installation only requires access from one side of the material. Installation: drill through the materials to be fastened, mount the rivet using a special tool. Of the characteristics of blind rivets, attention should be paid to the geometric dimensions (diameter and length of the rivet body). The type of rivet can be ordinary with a shoulder (D head = 2D rivet body, Fig. 1), with an enlarged shoulder (D head = 3D rivet body, Fig. 2), countersunk (Fig. 3) and blind with a water and gas tight body (Fig. four). Manufacture of details from a wire Usually factories let out a wire in rolls. Often the wire is covered with rust or scale, which are removed with sandpaper before starting to manufacture the product. The blanks of the desired length are cut with wire cutters (fig. on the right). The cut piece of wire must be straightened before processing. Straightening of soft wire can be done with wooden blocks (fig. left), with a hammer or mallet on a plate (fig. right), by moving the wire around a cylindrical steel mandrel (fig. left). You can straighten a thin and soft wire by stretching it between the nails driven into the board (see the figure on the right). To give the wire blank the desired shape, it is subjected to bending. Wire bending is carried out using pliers (fig. left) and round nose pliers (fig. below right). Pliers clamp and bend the wire at the desired angle. Details of a complex, curvilinear shape are obtained using round-nose pliers. For the manufacture of products in the form of rings, cylindrical mandrels are used (Fig. Left). Below are several options for wire products. Some of them are used in everyday life and jewelry. When cutting the workpiece, do not bring the wire close to the face. The mandrel must be securely fixed in a bench vise. You can only work with the right tool. You can not keep your left hand close to the bend of the wire blank. Cutting metal with a hacksaw To cut billets from long products, a hand hacksaw is used. A hacksaw blade is a thin band of hard steel with wedge-shaped teeth on one edge. Each tooth is a cutter. The hacksaw blade must be securely fixed in the frame (see figure on the right 5) with the tension screw (1), and the teeth must be directed in the direction opposite to the handle (4). Getting started, you should adjust the tension of the blade in the hacksaw frame. To do this, insert one edge of the blade into the rear head (3) and secure with a cotter pin. Insert the second edge of the blade into the cut of the front head (2) and tighten the blade with the tension thumb screw. Too much tension on the blade, as well as too little, can lead to breakage. According to the marking risk, a shallow cut is made with a trihedral file. This will ensure the exact direction of movement of the blade. During work, you need to take the correct working posture (see the figure on the left): become half-turned to the vise, put your left foot forward and place your feet at an angle to each other. The hacksaw is held with both hands while cutting. The position of the hands is shown in the figure below. The movement of the hacksaw is carried out only by hands, and the body remains motionless. This saves energy and ensures high quality work. A hacksaw can cut strip material only if three or more teeth of a hacksaw blade fit into its thickness. Thinner material is fixed between wooden bars (see figure on the right). Thin blanks are assembled in packages, that is, several pieces are put together and fixed in a vice. When cutting long workpieces, it is not always possible to complete the cut due to the fact that the machine frame rests against their end. Then the canvas is rotated with respect to the frame by 90 ° (see the figure on the left) and continue to work. When cutting with a hacksaw, shaped profile blanks (corner, channel, etc.) are recommended to be fixed in wooden muffs (see the figure on the right). At the beginning of cutting strip and square products, the hacksaw is tilted slightly forward. Gradually, the slope is reduced and after the cut reaches the nearest edge of the workpiece, the hacksaw is returned to a horizontal position. Care must be taken to ensure that the marking risk is preserved. If you cut exactly according to the marking risk, then after sawing off the size of the part will be less than that specified in the drawing, which will lead to irreparable marriage. The forward movement of the hacksaw is working, since at this time the teeth of the blade cut the metal, and the backward movement is idle. When moving the hacksaw forward, it is slightly pressed down, the reverse movement is performed without pressure. The stroke of the hacksaw must be full so that the blade wears evenly along the entire length. You need to move the hacksaw smoothly, without jerks, rhythmically. The speed of the hacksaw can be from 30 to 60 double strokes per minute. To reduce friction, the hacksaw blade is coated with machine oil or other thick lubricant. The workpiece must be securely fixed in a vise. It is necessary to work with a hacksaw smoothly, without jerks. When finishing cutting, it is necessary to loosen the pressure on the hacksaw and hold the part to be cut from below. Do not blow off the chips and sweep them away by hand. You have to use a brush. The illustration shows different options for hacksaws and various devices for sawing metal. Metal cutting By cutting, the workpiece is divided into parts, excess metal (allowance) is removed, lubrication grooves are made in the parts, etc. This operation is carried out using a chisel (fig. on the right) and a hammer. The cutting part of the chisel, like any other cutting tool, has the shape of a wedge. The angle of sharpening (sharpening) depends on the hardness of the metal being processed: the harder the metal, the greater should be the angle of sharpening. For steel, an angle of 60° is recommended, for non-ferrous metals - 35° ... 40°. To cut grooves, a special chisel is used - a cross-cut (fig. on the right). When cutting, hammers weighing 400 or 500 g are used. Before cutting, the workpiece is fixed in a vice slightly to the left of the right edge of the jaws, so that there is room for installing a chisel (fig. on the left). The hammer is placed with a striker to the left on the workbench to the right of the vise, and the chisel is placed on the left, with the cutting part towards itself. A protective mesh (or screen) must be installed at the working place for cutting to protect others from metal fragments. During felling, it is very important to adopt the correct working posture (fig. right). You should stand straight, the body of the body should be turned in relation to the vice, the right shoulder should be against the head of the chisel. The left leg for stability should be extended forward, the body rests on the right leg. The chisel and hammer are held so that the impact part and the edge of the handle protrude by 15 ... 30 mm (fig. on the left). Cutting in a vice can be performed according to the marking risks and according to the level of the vise jaws. In the first case, the workpiece is set so that the marking risk is 1.5 ... 2 mm above the vise jaws. The chisel is placed at an angle of 30 ... 40 ° (fig. on the right) to the surface to be treated. After each blow, the chisel is returned to its original position. In the second case, the marking risks are lowered below the level of the jaws in such a way that after processing an allowance of 1 ... 1.5 mm remains on the surface of the workpiece. Depending on the hardness of the material being processed and its thickness, blows of various strengths are applied to the chisel with a hammer. There are carpal, elbow and shoulder strikes (see the figure below). The wrist (Fig. a) blow removes small irregularities and thin chips, the elbow (Fig. b) - cut off excess metal and cut into pieces a workpiece of small thickness. With a wrist strike, the hammer moves due to the movement of the hand. With an elbow strike, the arm bends at the elbow and the impact becomes stronger (Fig. b). With an elbow blow, excess metal is cut down and the workpieces are divided into parts. Shoulder strike (Fig. C) - thick chips are cut, bars are cut, strips of great thickness. In cases where the workpiece cannot be fixed in a vice, it is processed on a plate (fig. on the left). The chisel is placed vertically on the marking risk and strikes. After each impact, the chisel is moved to half of the cutting edge. This makes it easier to place the chisel in the correct position and create a continuous cut. In a workpiece of great thickness, the marking risk is applied from opposite sides. First, they cut to about half the thickness of the sheet on one side, then on the other. When cutting out a workpiece of complex shape, the cutting edge is placed at a distance of 1 ... 1.5 mm from the marking risk and the workpiece is cut with light blows along the entire contour. After that, they cut along the entire contour with stronger blows. Then the workpiece is turned over and the cutting is completed along the outlined contour. You can only work with the right tool. The impact part of the chisel and hammer must be free of cracks and burrs. The hammer handle must be firmly seated and not cracked. Do not check the quality of cutting by hand. At the end of the cutting, weaken the force of impact. To avoid injury, a rubber washer should be put on the top end of the chisel. Cutting can only be carried out with a protective screen and goggles. You can not stand behind the back of the worker. Manual felling is a labor-intensive operation. AT industrial production it is replaced by other processing methods. Where it is impossible to do without felling, it is performed by fitters using pneumatic or electric chipping hammers. Most often, cutting blanks from sheet metal is carried out on presses using special stamps. Among the high-performance methods that have been used recently, oxygen, laser, etc. should be noted. These installations serve metal cutters. A variety of chisels and crosscuts are shown in the figure below. Sawing blanks from long products With the help of a file, a small allowance is removed from the blank, thereby ensuring that the part has the exact dimensions and shape indicated on the drawing. The main parts of the file are shown below. This is the nose; ribs; faces; heel; ring worn on the handle to prevent splitting of the handle. General form file and notch profile are enlarged in the figure on the left. Notch profiles are: 1 - single, 2 - double, 3 - rasp. Each notch - a file tooth - has the shape of a wedge. Files are made from tool steel. They differ from each other in the shape of the cross section, the type of notch, the number of notches per unit length and the length of the working part. Depending on the shape of the surface to be treated, files of one profile or another are selected (fig. on the right). So, for processing planes, flat files are used, spherical surfaces - semicircular, cylindrical holes - round, rectangular grooves and holes - square, and corners - trihedral. By the size of the teeth of the notch and their number per 10 mm of the length of the working part, files are distinguished (see the figure on the left): bastard files - 5-12 teeth (large notch); personal - 13-26 teeth (medium notch); velvet - 42-80 teeth (fine notch). Files with a very coarse cut are called rasps, those with a very fine cut are called needle files. Bastard files are used only for primary, rough surface treatment of workpieces. They work with personal files when the main layer of metal has already been removed with a bastard file. For filing with a personal file, a metal layer of no more than 0.2 ... 0.4 mm is left. With a velvet file, the workpiece is brought to the specified dimensions. The rasp is used to file soft metals, leather, wood, rubber. Files (fig. on the right) are used for filing small parts made of metal, plastic, wood. Before starting filing, it is necessary to properly organize your workplace, and above all, it is most rational to lay out the tools and workpieces on it. The marked workpiece is firmly clamped in a vise. In this case, the processing surface must be above the level of the vise jaws. When filing, it is necessary to take the correct working position (fig. on the left): you should stand half-turned to the workbench at a distance of 150 ... 200 mm from its front edge, put your left foot forward in the direction of the file. The rounded part of the file handle should rest against the palm of your right hand. Four fingers are wrapped around the handle, and the thumb is placed on top and pressed against the handle. The outstretched fingers of the left hand are placed on the toe of the file, stepping back from the edge by 20 ... 30 mm. During operation, the file makes reciprocating movements: forward - working stroke, backward - idle. During the working stroke, the tool is pressed against the workpiece; during the idle stroke, it is driven without pressure. The tool must be moved strictly in a horizontal plane. The pressing force on the tool depends on the position of the file (fig. right). At the beginning of the working stroke, the left hand presses a little harder than the right. When the middle part of the file is brought to the workpiece, the pressure on the toe and the handle of the tool should be approximately the same. At the end of the working stroke, the right hand is pressed harder than the left. There are several ways of filing: transverse, longitudinal, cross and circular. Cross filing (Fig. Left a) is performed when removing large allowances. With longitudinal sawing of workpieces (Fig. b), the straightness of the machined surface is ensured. It is better to combine these two filing methods: first, filing is done across, and then along. When filing with a cross stroke (Fig. C), good self-control over the progress and quality of work is ensured. First, they file with an oblique stroke from left to right, then, without interrupting work, with a direct stroke, and finish filing again with an oblique stroke, but from right to left. Circular filing (fig. d) is performed in cases where frequent irregularities need to be removed from the treated surface. The correctness of filing is checked with a ruler or square for clearance (fig. on the right): if there is no clearance, the surface is flat. The durability of files largely depends on how you care for them. You can work with a file with a serviceable and firmly attached handle. At the end of the work, the files should be cleaned of dust, sawdust, dirt, oily substances. Files are stored so that their notches do not touch each other. Sawdust from the surface of the product must be removed with a special brush. External thread cutting A thread is a helical groove formed on rotating parts. It is widely used for connecting parts to each other (fastening) and for transmitting movement (as, for example, in a lead screw lathe or vise). In threaded connections, bolts, studs and screws are used. Bolt - a cylindrical rod with a head at one end and threaded at the other (see figure on the right a). Hairpin - a cylindrical rod with a thread on both ends. One end of the stud is screwed into one of the parts to be joined, and the part to be fastened is installed on the other end and the nut (b) is screwed on. Screw - a cylindrical rod with a thread for screwing into one of the connected parts and a head of various shapes (c). The main elements of the thread: helix angle a, thread pitch p, profile angle y, outer and inner diameters (fig. on the left). Depending on the purpose of the threaded connection, different thread types . In the direction of the turns, the thread is right and left (fig. right). Most often cut the right thread. For cutting external fastening threads, a special tool is used - dies. They are round (fig. on the left a), thread-rolling (b) and sliding (c). The round die (fig. on the right) is made in the form of a hardened steel nut. The die thread is crossed by through longitudinal holes. The formed cutting edges in the form of a wedge and a groove ensure cutting of the workpiece and simultaneous chip exit. In order for the end of the rod (blank) to better enter the die from the end sides, its thread has a lower profile height. This is the so-called fence part. Round dies in accordance with the standard are provided for cutting metric threads with a diameter of 1 to 76 mm. They are laid in the sockets of the die holder and fixed there with studs (or bolts) with a slot for a screwdriver. Die 4 (fig. on the left) with special cutouts 6 is fixed in the die holder 5 or in the knob with three or four screws, depending on its size and operating conditions. One or two screws 7 serve for fixing, screws 1 and 3 - for fixing and compressing the die when adjusting its size after cutting through the jumper. The die is unclenched with the help of screw 2. Adjustable threaded rollers are installed in the body of the thread rolling die (Fig. b above). The metal of the workpiece is not cut, but extruded. Due to this, the surface of the thread is cleaner, and the thread itself is better and more accurate. Sliding prismatic dies (Fig. c above) consist of two sliding and retracting half-dice. Of particular interest is a knob for installing and fastening dies (fig. on the right) with an additional guide ring 16, which helps to maintain direction on cylindrical blanks 12 (rods, mold pushers and screws, die removers). An additional device can be used in conventional collars. In the inner part of the holder 1 of the collar there is a machined square window with inserted prismatic dies. A screw 15 is installed on the side of the holder, which presses the rams 9 during operation, and on the sides of the holder, two handles 13 are screwed into the body 11 for gripping by hands. In the lower part of the cage there is a washer 14, fixed with screws 8, and two guide pins 10, along which the ring 16 moves. ). These data are indicated on the plate. Then, according to the table (see table below), determine the diameter of the rod for this thread and select the workpiece. In this case, it must be taken into account that when a thread is cut, metal, especially copper, mild steel, "stretches". As a result of this, the diameter of the rod increases slightly and the pressure on the threaded surface of the die increases. It heats up, the chips stick to the cutting edges, and the thread becomes "torn". All this reduces its quality. Therefore, the diameter of the rod must be less than the outer diameter of the thread by 0.1 ... 0.3 mm, depending on the size of the thread. If the diameter of the rod is less than 0.4 ... 0.5 mm of the outer diameter of the thread, then the thread profile is incomplete. The selected workpiece must be straightened, marked, cut off according to the markup and, fixing it in a vice, chamfer with a file (Fig. right a) so that the intake part of the die captures the metal more easily. The quality of the die should be checked by external inspection and by screwing it onto a bolt or stud with an intact thread. It is also necessary to carefully check the quality of fastening the die in the die holder in order to exclude its possible distortion and slippage in the socket. Before threading, its length is marked on the rod, the rod is fixed in a vice so that the end protruding above the upper plane of the jaws is 20 ... 25 mm larger than the cut part. The rod is placed on a square at an angle of 90 ° to the upper planes of the jaws (Fig. b). The die, fixed in the die holder, is placed on the upper end of the rod and, with a slight pressure, without allowing the die to skew, rotate it (Fig. c). After cutting 1-2 threads of the thread, the coincidence of the axes of rotation of the die and the rod is checked again. After that, the threaded part of the rod, the cutting of the die are lubricated with oil and the die is rotated, evenly pressing both handles of the die holder (Fig. d). The rotation should be reciprocating: one or two turns to the right and half a turn to the left. In this case, the chip breaks, exits through the longitudinal hole. This makes threading easier and improves thread quality. The quality of the cut threads under production conditions is checked with thread micrometers, threaded ring gauges and threaded plugs (see the figure on the left). In school conditions, it is allowed to check the thread with nuts. After finishing work, the die is removed from the die holder, thoroughly cleaned with a brush from chips, wiped with a rag and lubricated with oil. Threading with a die can also be performed on a lathe. When cutting threads, the die should be securely fixed in the die holder. When working, be careful not to get your hand between the die holder handle and the support. Use a brush or oiler to lubricate. Do not blow the chips off the die, but use a sweeping brush. Do not allow oil to come into contact with clothing or hands. In factories, hardened screws are used, which are driven through punched holes in two or more sheet metal parts to be joined. Screws, cutting threads in the holes, connect these parts. This method of threaded connection is economical and speeds up the assembly process. Many factories now use hardened self-drilling screws for steel and cast iron parts that are less hard than the screws. Threads on bolts and studs of small diameter are made on automatic lathes simultaneously with the manufacture of the bolts themselves. Screws and bolts are also stamped on presses. In mass production, knurling of external threads is widespread. After the passage between the rollers, a thread is formed on the rod. Some threaders use carbide inserts instead of rollers. The main terms and concepts that are necessary for mastering the material are described below. The main elements of the thread: The outer diameter of the thread is the diameter of an imaginary cylinder, the surface of which coincides with the tops of the external thread and the troughs of the internal thread. Internal thread diameter - the diameter of the cylinder, the surface of which coincides with the tops of the internal thread and the troughs of the external thread. Mean thread diameter - the diameter of an imaginary cylinder coaxial with the thread, the generatrix of which intersects the thread profile at the point where the groove width is equal to half the thread pitch. Profile angle - the angle between the sides of the profile, measured in an axial section. The top of the profile is a section of the profile that connects the sides of the ledge. Profile cavity - a section of the profile connecting the sides of the groove. Thread pitch - the distance between adjacent profile flanks of the same name in a direction parallel to the thread axis. Thread helix angle - the angle formed by a tangent to a helix to a point lying on the average thread diameter and a plane perpendicular to the thread axis. Profile angle - the angle between the sides of the coil, measured in a plane passing through the axis of the thread. Thread system. The following threads are used in industry: Metric thread - has a triangular profile and serves mainly to connect parts to each other. Metric threads are divided into two groups: metric coarse threads and metric fine threads for diameters 0.25-600 mm. Pipe conical thread - has the same purpose as cylindrical. The required tightness of the connection is achieved by deformation of the conical pipe threads. Conical inch thread with a profile angle of 60 degrees. Conical inch thread is used to obtain tight connections. Inch thread - used for fastening machine parts with bolts, screws and studs. Trapezoidal threads - are used mainly for lead screws of machine tools and other power transmissions. Trapezoidal threads are divided into large, normal and small. Thrust threads - large, normal and small - are used mainly for running and cargo (with a large load) screws with a unilaterally acting load. In rare cases, they are used as fasteners. Rectangular thread - used for cargo and lead screws. The thread is difficult to manufacture and has disadvantages that limit its use. Cylindrical pipe thread - cylindrical pipe thread is used in connections of hollow thin-walled parts, when the connection must be especially tight. Modular thread - used for worms. Scheme of helix lines: a - development of the helix; b - cylindrical triangular thread; c - cylindrical square thread; g - cylindrical rectangular thread; d - cylindrical trapezoidal thread; e - cylindrical round thread; g - single thread; h - two-start thread; and - three-start thread. In order to find out the thread pitch, special gauges are used (see the figure on the right). Cutting an internal thread An internal thread (thread in a hole) is cut with a tap (fig. right). Taps are made from tool carbon, alloy or high speed steel. The tap consists of a shank and a working part. With a shank, the tap is attached to the collar or chuck of the machine. The working part of the tap is a screw with longitudinal or helical grooves for threading. As with dies, the working part of the tap has a chamfer to facilitate the entry of the tool into the hole. Helical grooves, similar to the longitudinal holes in the die, form cutting edges. The shavings come down on them. Manual taps for cutting metric threads are produced in a set that includes two taps for threads up to 3 mm in diameter and three (No. 1-rough, No. 2 - medium and No. 3 - fine) for threads with a diameter of more than 3 mm. The rough tap does the bulk of the work and cuts up to 60% of the metal layer to be removed. The semi-finishing tap cuts up to 30% of the metal layer. The finishing tap gives the thread its final shape and dimensions and cuts off the remaining 10% of the metal layer. The taps included in the kit have different diameters of the threaded part and different shapes of profiles. On the tail part of all the taps of the set, circular risks (1,2,3) are stamped or the numbers of the taps are affixed, and the thread sizes are indicated - diameter and pitch. To rotate the tap when cutting threads by hand, a device is used - a crank (fig. on the left). There are collars - unregulated (fig. a) and adjustable (fig. b). Before proceeding with threading in the hole, mark the place of the hole with its obligatory punching. Taking into account the dimensions of the future thread according to the table (see table below), the diameter of the drill is selected. Thread diameterDrill diameterThread diameterDrill diameterCast ironSteel Cast iron Steel ,43,512,010,010,1 Sometimes you can use a simple method - to find out the diameter of the hole under desired thread subtract the pitch from the thread diameter to get the hole diameter. The size of the threaded hole diameter can be calculated by the formula D=d-1.6t, where D is the hole diameter, mm; d is the diameter of the thread being cut, mm; t - thread depth, mm. The dimensions of the knob for fixing the tap when threading are selected depending on the diameter of the thread being cut. The approximate length of the collar can be determined by the formula L=20D+100 mm, where D is the thread diameter. When cutting an internal thread, the metal is squeezed out, as it were, reducing the diameter of the hole. Therefore, the diameter of the drill should be slightly larger than the inner and smaller than the outer diameter of the thread. If the hole diameter is less than required, the tap will break, and if it is larger, the thread will be incomplete, weakened. The drilled hole is processed with a countersink. The use of this tool allows you to improve the quality, reduce the taper, ovality of the side surface of the hole. A countersink works in the same way as a drill. For high-quality threading, it is important to correctly fix the part in a vice and install the first tap in the hole (fig. above a). The part is fixed so that the surface with the hole is parallel to the planes of the vise jaws, and the tap is perpendicular to the plane of the part and the jaws. Perpendicularity (angle 90 °) is checked with a square (Fig. b). The thread is cut as follows (fig. c). First, tap No. 1 is installed. Its threaded part is preliminarily lubricated with oil. Pressing the collar with the left hand to the tap, with the right hand smoothly rotate it to the right until the tap cuts 1-2 threads. At the same time, they monitor the preservation of the right angle, if necessary, directing the tap. After the tap has taken the correct stable position and threading has begun, the knob is taken with both hands and rotated with light pressure, intercepting every half turn. In order for the chips to break and go into the grooves of the tap, it is rotated back and forth: one and a half turns forward and half a turn back. Having finished the passage with tap No. 1, it is turned out, tap No. 2 is inserted, threaded, the knob is installed and cut. The thread is finally finished with tap No. 3 and the thread is checked (Fig. d). Blind threaded holes are drilled to a depth slightly greater than the length of the thread. The quality of the thread can be checked in the workshop by screwing the appropriate bolt into the hole. When cutting threads, the following defects sometimes occur, which should be avoided: 1) rough or torn cutting - obtained if there is no lubrication, and also due to a skewed tap or die; 2) incomplete profile thread - if the diameter of the hole is greater than the norm or the diameter of the rod is less than the norm; 3) thread misalignment or breakage of the tap - if the diameter of the hole is less than the norm or the diameter of the rod is more than the norm. When cutting threads in ductile and soft metals, it is necessary to periodically unscrew the tap and clean the grooves from chips. Threads should be cut sequentially with a full set of taps. Care must be taken to ensure that there is no distortion of the tap. Special care must be taken when threading blind holes. Be sure to periodically lubricate the cut thread with oil.
Target: Formation of knowledge among students about the concept of stripping sheet metal, wire, plastic.
Tasks:
- educational: give the concept of cleansing; introduce the tools used in cleaning;
- developing: to form the skills of proper work during stripping; develop mindfulness;
- educating: to cultivate accuracy in work.
Lesson type: combined lesson.
Methods and forms: consolidation of the material covered, explanation of theoretical information, practical work.
Equipment: posters, files, sandpaper.
Equipment and materials for performance practical work: files, sheet metal blanks.
DURING THE CLASSES
I. Organizational moment.
II. Lesson topic.
Cleaning of sheet metal, wire, plastic.
The purpose of the lesson: Formation of knowledge among students about the concept of stripping thin sheet metal, wire, plastic
III. Repetition of the studied material.
Poll students on the studied material.
- What is lumber and wood products.?
- What is wood?
- The purpose of a carpentry workbench?
- Sequence of manufacturing parts from wood?
- Marking wood blanks?
- Graphic representation of wood details?
IV. Learning new material.
Teacher:
Cleaning is the process of removing surface defects. CLEAN - smooth, level (end, edge, surface of something). Z. with a file. Z. slice.
Types and sizes of files
Each type of notch has its own advantages and is used for files of a certain purpose.
A simple or single notch is used in the manufacture of certain types of special files (for example, for sharpening saws on wood). It is advisable to use files with a simple notch in all cases when it is required to remove an insignificant layer of metal from a narrow work surface.
Cross, or double, notch is used in the manufacture of general-purpose bench files. In these files, the main notch is made at an angle λ = 25°, and the auxiliary notch is made at an angle ω = 45° (Fig. 1g).
These notch angles provide high productivity.
Dot, or rasp, notch is used in the manufacture of rasp files. Rasps with a point notch have large teeth and capacious grooves, which contributes to better chip separation when filing soft metals, rubber, leather, plastics, etc.
Locksmith's files differ in two main ways: in the shape of the cross section and in the number of notches per centimeter of the length of the file.
Locksmith's files (GOST 1465-59) are made according to the cross-sectional shape of eight types: flat (type A), flat pointed (type B), square (type C), trihedral (type D), round (type D), semicircular (type E), rhombic (type Zh), hacksaw (type K).
According to the number of notches, bench files are divided into six numbers: 0, 1, 2, 3, 4, 5. The notch number is an indicator of the operational purpose of the size range of files according to the pitch of the main notch.
Files with a notch No. 0 and 1, the so-called bastard ones, have the largest teeth and are used for filing parts with an accuracy of 0.2-0.5 mm with a processing allowance of 0.5 to 1 mm.
Files with a notch No. 2, the so-called personal ones, are used for fine filing of parts with an accuracy of 0.02-0.15 mm, while the processing allowance is from 0.1 to 0.3 mm.
Notched files No. 3, 4, 5, the so-called velvet files, are used for finishing parts with an accuracy of 0.01 to 0.005 mm, while the processing allowance ranges from 0.025 to 0.05 mm.
Files are made from tool carbon steel U13 or U13A and hardened for hardness not lower than HRC 54-58.
Rasps differ from metalwork files in a notch, their teeth are large and short in the form of pyramids. The large teeth and large grooves behind each tooth make the rasps suitable for filing soft metals. The teeth of the rasp are arranged in rows perpendicular to its axis. To avoid grooves when filing, the rows are offset relative to each other by half a step between the teeth.
In the copper and tinsmith business, general-purpose rasps (GOST 6876-54) are used for filing parts made of soft metals (aluminum, duralumin, etc.). General purpose rasps are made in four types: flat blunt, flat pointed, round and semi-circular. Rasps of all four types are made in lengths of 250 and 350 mm.
For the manufacture of rasps, tool carbon steel is used, mainly grades U7A, U10A, hardened to a hardness of HRC 35-40.
The smallest files, the so-called needle files, are designed for very fine and precise work. They differ in the shape of the cross section and in the number of notches per centimeter of the file length.
Needles (GOST 1513-67) are made according to the cross-sectional shape of eleven types: flat blunt, flat pointed, square, trihedral, trihedral one-sided, round, semicircular, oval, rhombic, hacksaw and slot.
According to the number of notches, the needle files are divided into six numbers: 1, 2, 3, 4, 5, 6.
Files flat blunt, flat pointed, square, trihedral, round, semicircular, rhombic, grooved are made in two sizes: along the length of the working part 60 and 80 mm and the length of the shank, respectively, 60 and 80 mm.
Three-sided, oval triangular needle files are made in three sizes: along the length of the working part 40, 60, 80 mm and the length of the shank, respectively, 80, 60, 80 mm.
Hacksaw files are made in three sizes: along the length of the working part 60, 80, 40 mm and the length of the shank, respectively, 60, 80, 80 mm.
Files are made from tool carbon steel U12 or U12A and hardened to a hardness of HRC 54-60.
The file has a wooden handle with a clamping ring, which prevents it from cracking when placed on the file shank. The handle should fit tightly on the file shank, for which a hole is drilled in it with a diameter corresponding to the size of the middle part of the shank and a depth equal to the length of the shank. Then, with a red-hot shank of an old file of the same size, a hole is burned out exactly in the shape of the shank for 2/3-3/4 of its length. When putting the handle on the shank, do not hit the file with a hammer, as its cutting part may break. When properly put on, the handle is hit against the locksmith's workbench until it sits tightly on the shank. When putting the handle on the file shank, make sure that it is put on without skew.
Handles are made of wood (birch, beech) or pressed paper. Wooden handles are used more often, as they are more practical. The length of the handle should be one and a half times longer than the file shank.
Handles for general-purpose files are made 90, 100, 110, 120, 130, 140 mm long, with a diameter of 12, 16, 20, 23, 25, 28 mm, respectively. The size of the handle is selected according to the size of the file.
To achieve a good result, the file is moved diagonally to the part, often changing the direction of its movement due to its location or rotating the vise.
Of course, a person is not a robot, so that every file movement can be kept strictly horizontal, even experienced craftsmen have slight deviations from ideal file movements.
In order not to increase these errors, the direction of the file should be changed frequently.
V. Consolidation of the studied material.
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Product finishing
Product finishing from sheet metal and wire in the training workshop includes stripping cr omok, grinding parts and coloring. These operations give the product a beautiful appearance and increase its resistance to wear and corrosion.
For this purpose, products made of thin sheet metal and wire are cleaned file and grinding wheel crusty and cover paint or varnish.
The edges are cleaned with a fine-grained file. With it, remove burrs, dull sharp corners. Small irregularities, scratches are removed with a sandpaper. For the convenience of cleaning the edges of sheet metal blanks, it is recommended to fix them between two wooden planks in a vise. Thin and short parts are processed on a sheet of sandpaper. The parts are pressed with a wooden block and, with some effort, are moved back and forth along the surface of the skin.
Before painting or varnishing the surface, the parts are degreased with special solutions (as directed by the teacher) or wiped with a cotton swab dipped in a soda solution.
Paint or varnish is applied to a dry surface by spraying from cans or with a brush evenly over the entire surface (see figure on the right).
The oil paint applied with a brush is carefully rubbed in all directions. Enamel paint (enamel) is applied without rubbing. The second layer of paint or varnish is applied after the first has dried. In this case, the paint layer becomes even, and the painted surface takes on a beautiful appearance. Coating with paint or varnish protects the surface of products from corrosion.
Brushes are stored in a glass jar with water or in a special suspension.
The coating of surfaces of metal products with oxide films is widely used - oxidation. For this purpose, the product is heated in a muffle furnace and cooled in a special solution (prepared by the teacher). The surface of such products has a black or dark blue color. This finishing method is called bluing (blackening).
Fast blackening(similar to bluing and oxidizing) is the process of imparting a beautiful, uniform black decorative and protective coating to metal products at room temperature.
At enterprises, anti-corrosion finishing of metal products is carried out tinkers (tin plating), electroplating (electrolytic coating with chromium, nickel and etc.), metallizers (coating with any sprayed metal). Workers in these specialties must have a good knowledge of the properties of metals and alloys and the arrangement of installations for finishing products.
Carry out painting and varnishing work in a ventilated area.
Keep hands and clothes clean.
Do not touch eyes and face with dirty hands.
Do not paint products near heating devices.
Wash hands thoroughly with soap after finishing work.
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