Technological features of equipment and tools for metal cutting. Metal chopping purpose and purpose of metal chopping The tool for chopping metal is

One of important stages In the production of blanks and processing of rolled steel, metal cutting is carried out. An alloy is a material that is highly hard, so special equipment is needed to cut it.

The essence of metal cutting

The cutting technology consists of cutting off excess parts of metal using special tools. Used in cases where processing does not require high precision. Most often, cutting sheet metal is necessary to separate scale and inaccuracies that arose during production. The technology is also used for removing burrs, dividing into parts source material. Chopping is a metalworking operation that is performed both manually and using special devices. In the first case, chisels, hammers, and cross-sections are used. It should be noted that metal cutting is a rather difficult process, so its automation greatly simplifies cutting.

What tools are used for manual chopping?

Metal cutting is done using chisels. They are made from tool steel (U7, U8). The edge of such a tool is a blade of great hardness (not less than 53 HRC). Depending on the hardness of the metal being processed, the chisel can be sharpened at an angle of 60° (for steel), 70° (bronze, cast iron), 35-45° (for non-ferrous metals). Less acute angle when processing hard materials necessary so that the end of the chisel maintains its strength and does not break. The tool head, as a rule, has less hardness (so that it does not collapse when hit by a hammer). It gradually wears out and becomes deformed, so it needs to be adjusted. Under no circumstances should you work with damaged chisels, as the hammer may slip and cause injury to the worker.

Kreuzmeisel, hammers

Tools for chopping metal include such a device as a crossmeisel. This is the so-called groove chisel. Designed for making special grooves, grooves, and other holes. Its working surface has a narrower blade width. Figured grooves are made with a similar device - a groover. As percussion instrument hammers are used. They come with both round and square sides, weight is 400-800 grams. It is the hammer that strikes the chisel (crosspiece). To ensure that its working surface is securely fixed and does not slip off the handle, special metal or wooden wedges are often used, which are driven into it. There are different methods of striking: wrist, elbow, shoulder. The brush blow is used to separate thin chips, remove minor irregularities. Cutting grooves and grooves requires an elbow strike. The full swing (shoulder strike) has maximum force. It is necessary when processing thick metal.

Material cutting options

Depending on the location of the tool and the part, vertical and horizontal cutting are distinguished. The first is performed on a slab, an anvil. The part is placed on work surface horizontally and the instrument is held vertically. After striking, the blade is moved so that part of it (about half) is in the newly formed hole. This is necessary to ensure continuous cutting of metal. If the sheet thickness is more than 2 mm, markings must be applied on both sides. First, the part is processed on one side, then turned over. If the material thickness is small, it is recommended to place a sheet under the workpiece mild steel. This will prevent the chisel from getting dull on the anvil. Horizontal cutting (bending) of metal occurs in a vice. In this case, the working tool is mounted at a very small angle to the surface being processed (almost horizontally).

Industrial scale cutting

At enterprises, metal is cut using the following methods: cutting with a band saw, laser, gas, abrasive cutting (with a mixture of water and abrasive material). Laser cutting of metal is based on the use of laser heat, due to which the cutting line is heated to the melting temperature. At the same time, the base material does not heat up and retains its properties. This type processing is highly efficient, the workpiece after cutting does not require any additional processing. However, this method is characterized by high equipment costs. There are also requirements for the thickness of the material - it should not exceed 20 mm. Waterjet cutting eliminates strong thermal effects on the material, the edges do not melt, and the accuracy and quality of the cut are high. Gas treatment is based on directing a stream of oxygen to the part, which burns through the metal. Variety this method- flux-oxygen technology. The method of cutting metal using a guillotine is widely used.

A very popular method of cutting alloys is the use of a guillotine. They are manual, electromechanical, hydraulic, pneumatic. When choosing a guillotine, the serial production and the thickness of the metal that needs to be cut are taken into account. For thin sheets(about 1 mm) fits well manual equipment. Hydraulic drive has great power, all operations are performed at high speed. Such machines do not have much vibration, their maintenance is not difficult, and the cutting accuracy is high. Using an electromechanical drive, metal cutting up to 8 mm thick is carried out. These devices are powerful, safe, and have many additional features.

How metal is cut on a guillotine

The machine is equipped with two knives, one of which is stationary, and the second can make circular movements. The metal is fed by a roller table to the cutting site. The knife is lowered to the marked place, and the workpiece is chopped into the necessary elements. The knife is controlled through a special button. The cutting tool creates a lot of pressure, so there are no burrs and the edges remain smooth. This type of metal cutting has many advantages. Firstly, the cost of the process is low, there are practically no residues and waste. Secondly, the quality of the resulting products is quite high. They can be immediately subjected to further technological processing - painting, drilling, etc. However complex configurations parts cannot be manufactured using such equipment. All modern models guillotines are equipped with a large number of electronics. This allows cutting metal blanks almost fully automatic.

The chisel is a shock- cutting tool, designed for cutting or chipping metal and stone. It is a steel rod with double-sided sharpening and a flat butt designed for striking. The design of the chisel can position it as hand tool or as an attachment for fixing in a hammer drill. The cross-section of the rod can be in the shape of a circle, rectangle, oval or polyhedron. To reduce the risk of injury, an expanding mushroom made of rubber or other metal can be installed on the striking part of the tool, providing a more comfortable hammer hit and dampening recoil.

Scope of application

The tool is designed for mechanical impact with destructive force. The scope of its use is quite extensive, but in most cases it is limited to:

By chipping stones.
Metal chopping.
By knocking down ceramic tiles.
By beating off the rivet heads.
Unscrewing bolts and nuts with torn edges.

To work, you need to lean the sharp part of the chisel against the surface that needs to be knocked off, chipped or cut, and then apply a strong blow to the butt of the tool with a hammer. If it is necessary to unscrew a bolt or nut with torn edges, then the sharp edge is leaned at an angle, after which several light taps are applied to obtain a notch. After a groove is formed on the surface of the metal, several powerful blows are made to the butt of the chisel. In this case, the direction of the push force must correspond to the movement of the thread for unwinding. After using a chisel, the nut or bolt becomes completely unusable.

Types of chisels and their purpose

Although the tool has the simplest design, there are several varieties of it designed to perform specific tasks.

The following types of chisels exist:

Metalworking.
Kreuzmeisel.
Ditcher.
Pike.
Kuznechnoye.
Boaster.

Metalworking The chisel is designed for cutting unhardened metals. It is quite sharp and can be used both for marking on sheet material and for unwinding bolted connections, knocking down rivets and other impromptu tasks. The cutting tip of the tool is slightly wider than the rod. The two-sided slopes gradually taper. Sometimes you can find a microchamfer on a chisel.

Kreutzmeisel a fairly recognizable tool with a narrowed cutting edge, which allows cutting out grooves and various grooves. Such a tool is more highly specialized than a metalworking tool, and therefore is not found as often. However, they can be completely used when knocking down ceramic tiles or rivet heads if there is no more suitable tool at hand.

Ditcher- This is an even more narrowly focused tool designed for cutting out figured channels. It is usually used when necessary hand cutting gaskets for cylinder head made of hard sheet material, as well as other specific tasks when it is impossible to get by with another tool. Form cutting edge can be wavy, semicircular, oval and U-shaped.

Pike It is practically an ordinary chisel, the tail part of which is narrowed. In its design, instead of an impact cap, the rod is ground to a smaller diameter, which allows fastening into a clamping chuck. The shape of the cutting edge can be point, narrow or wide, like a chisel.

Kuznechnoye a chisel can have a wide variety of cutting part shapes. Its main difference is the presence of a special groove in the tail section for the possibility of attachment to a wooden or metal handle. When assembled, it looks a bit like a sharp hammer. The tool is used for chopping or punching holes in red-hot metal. The presence of an elongated side handle allows you to protect the blacksmith’s hands from heat and flying sparks. There are also tools whose handles are welded using electric welding.

Boaster- This is a sharper tool designed for working with stone. Often its working part resembles a spatula. The tool is designed for smooth processing of stone and in most cases is used by sculptors. Typically, a wide rubber mushroom is provided in the striking part of the tool, which is not only designed to protect the hand holding the rod, but also to block the scattering of small pebbles.

How to distinguish a chisel for metal from a tool for stone

Individual designs of tools for different purposes can be very similar, so it can be difficult to figure out which one is intended for metal and which for stone. If the cutting edge is very wide in the shape of a spatula, then this is undoubtedly a tool for working with stone. Tools for metal are always solid cast from one material. It undergoes special hardening, as a result of which the cutting edge is harder than the rod at the shank, which is struck with a hammer. This prevents cracking in case of strong impact. Most stone chisels have carbide tips instead of a cutting edge, which can be easily seen. They provide easier chipping, but are completely unsuitable for metal where chopping is needed.

Tool sharpening

The sharpening angle of the chisel is usually 35, 45, 60 and 70 degrees, depending on its purpose. In most cases, the cutting edge of the tool does not have a microchamfer, so it does not differ razor sharp. To prevent the blade from chipping, it is always slightly dull, but such precaution still cannot completely protect the tool from complete loss of cutting properties. Over time, the cutting edge may deteriorate greatly and will require sharpening. This can be done using sandpaper.

Before starting work, you should prepare a small container with clean water, into which it will be necessary to dip a heated tool to prevent softening of its factory hardening. Sharpening of the tool is carried out along the end part of the emery wheel. The chisel blade is set against the direction of rotation of the emery machine. As a result, sparks should go to the floor. Turning the striking part away from you is not allowed. Depending on the power of the emery, as well as the temperature environment, cooling of the instrument in water should be carried out at intervals of 30 seconds to 1 minute. If you overexpose the edge, it will heat up excessively and lose its hardness, after which it will not be able to cut hard metals.

When sharpening, it is necessary to periodically change the side of contact of the cutting edges, since the chisel has two-sided slopes. Systematic turning allows you to maintain the correct geometry. If you don’t have sandpaper at your disposal, sharpening can be done on a whetstone. In this case, you will have to devote significantly more time. Movement along the block should also be carried out with the blade forward.

Chisels, kreutz-meisel and groovers are used as cutting tools when cutting metals (Fig. 35). Chisels for cutting hot metal are called blacksmith's, and for cutting cold metal - metalworking.

The metalworking chisel consists of three parts: working, middle and impact.

During cutting, the required shape of a part is achieved by breaking the connection between metal grains with the cutting edge of the tool and removing excess metal in the form of chips. In this case, the cutting part is given the shape of a wedge. The chisel is the simplest cutting tool in which the wedge is especially clearly defined (Fig. 36).

The effect of a wedge-shaped tool on the metal being processed varies depending on the position of the wedge and the direction of the force applied to its base.

There are two main types of wedge operation:

1) the axis of the wedge and the direction of the force applied to its base,

Rice. 36. Scheme of the cutting process when working with a chisel: a - distribution of forces on the wedge; b - influence of the sharpening angle on the cutting process; c - the process of chip formation during cutting and the geometry of the chisel

Perpendicular to the surface of the workpiece (Fig. 36, a). In this case, the workpiece is cut (splits) (Fig. 36, b)

2) the axis of the wedge and the direction of action of the force applied to its base form an angle of less than 90° with the surface of the workpiece. In this case, chips are removed from the workpiece (Fig. 36, c).

The shape of the cutting part (Fig. 36, c) and its sharpening angles determine the geometry of the cutting tool (chisel).

The following surfaces are distinguished on the workpiece: machined, machined, and cutting surface.

The surface being processed is the surface from which a layer of material (chips) will be removed.

The treated surface is the surface from which a layer of metal (chips) has been removed.

The edge along which the chips flow during cutting is called the front edge, and the edge opposite to it, facing the workpiece surface being processed, is called the back edge. The intersection of the front and rear edges forms a cutting edge, the width of which on a chisel is usually 15-25 mm.

The angle formed by the sides of the wedge is called the point angle; it is denoted by the Greek letter 3 (beta). The angle between the front edge and the machined surface is called the cutting angle and is designated by the letter 8 (delta). The angle between the front edge and the plane drawn through the cutting edge perpendicular to the surface being machined is called the front angle and is designated by the letter y (gamma). The angle between the rear edge and the machined surface is called the clearance angle and is denoted by the letter a (alpha).

The smaller the sharpening angle, the less effort must be applied to perform cutting. Therefore, the value of the sharpening angle is chosen depending on the hardness of the metal being processed and the tool itself. The greater the hardness and fragility of the metal, the stronger its resistance to penetration of a wedge into it and the greater the sharpening angle of the chisel should be. For cutting cast iron and bronze take p = 70°, for medium hard steel p 60°, for copper and brass p 45°, for aluminum and zinc p = 35°

The larger the rake angle, the easier the chips are separated. However, as the rake angle increases, the sharpening angle of the tool decreases, and therefore its strength. Therefore, the value of the rake angle is also selected depending on the operating conditions of the tool.

The clearance angle is of less importance in the cutting process; its purpose is to reduce friction between the tool and the machined surface. The clearance angle is usually 3-8°

The middle part of the chisel has a shape that is convenient for holding it during chopping. Usually this part of the chisel has rectangular section with oval edges or a polyhedron shape.

The chisel head is always made in the form of a truncated cone with a semicircular upper base. With this head shape, the force of hitting the chisel with a hammer is used with the greatest effect, since the applied blow always falls in the center of the striking part of the chisel. The conical head, in addition, rivets less during operation.

Chisels are made in lengths of 100, 125, 160, 200 mm, the width of the cutting edge is 5, 10, 16, 20 mm, respectively.

Chisels 100-125 mm long are used for small work, and 150-200 mm long for rough work.

The quality of the chisel is determined by compliance with the established heat treatment regime (hardening and tempering) and correct sharpening. Hardening of the working part of the chisel is carried out by heating it for a length of 40-70 mm to a temperature of 800-830 ° (light cherry-red color of heat) and cooling in water for a length of 15-30 mm, followed by tempering until purple tarnish.

The chisel head is hardened in the same way at a length of 15-20 mm with tempering up to gray tarnish.

The degree of hardening of the chisel can be determined with an old file, which is passed along the hardened part of the chisel. If the file does not remove chips from the hardened part of the chisel (only barely noticeable marks remain on it), the hardening is done well.

The Kreutzmeisel (Fig. 35, b) differs from the chisel in having a narrower cutting edge. It is used for cutting out narrow grooves, keyways, etc. To prevent the crosspiece from getting jammed as it goes deeper into the groove, its cutting edge is made slightly wider than the working part that follows it. However, quite often it is used to cut off the surface layer from a wide cast-iron slab: first, grooves are cut with a crossmeisel, and the remaining protrusions are cut off with a chisel. The materials for making the crosspiece and the sharpening angles, the hardness of the working and impact parts are the same as for the chisel.

To cut out profile grooves - semicircular, dihedral, etc., special edges are used - tsmeisel, called groovers (Fig. 35, c), which differ from the crossmeisel only in the shape of the cutting edge. Groovers are manufactured with pointed and semicircular cutting edges. Their dimensions depend on the diameter of the bearing shells and bushings in which the lubrication grooves must be cut.

Groovers are made of U8A steel with lengths of 80, 100, 120, 150, 200, 300 and 350 mm.

It should be noted that the operation of cutting grooves is labor-intensive and responsible; After cutting, the grooves often turn out uneven, with unequal depth, etc.

When sharpening chisels and crosspieces, simple sharpening machines are usually used. The tool to be sharpened is placed on the tool rest 1 of the sharpening machine (Fig. 37, a) and with light pressure it is slowly moved across the entire width of the grinding wheel. Sharpening should be carried out with cooling in water. In this case, you need to ensure that the heating

The tool did not exceed 120“; heating above the specified temperature leads to tempering and reduces the hardness of the cutting edge of the tool. During the sharpening process, the chisel (crossmeisel) should be turned first on one side or the other, this ensures uniform sharpening. The cutting edge of the chisel after sharpening should have the same width and inclination to the chisel axis. The sharpening angle of the chisel or crosspiece is checked using a template, which is a plate with angular cutouts of 70, 60, 45 and 35°. When sharpening a chisel or crosspiece, it is necessary to close the protective screen 2 and the safety casing 3.

After sharpening the chisel or crosspiece, burrs are removed from the cutting edges. The value of the sharpening angle is checked with a template, which is a plate with angular cutouts of 70, 60, 45 and 35° (Fig. 37, b).

Percussion instrument. Types of impact instruments include hammers of various purposes and designs.

Bench hammers are made in two types: with square and round heads (Fig. 38, a, b). The manufacturing process of hammers with a square striker is simpler, they are cheaper and therefore are widely used in metalworking practice. At the same time, hammers with a round striker have the advantage that they have a large weight advantage of the striking part over the rear, providing greater force and accuracy of the blow.

The choice of hammer by weight is essential. The weight of the hammer should match the width of the cutting edge of the chisel. Practice shows that for a normal impact when chopping metal, each millimeter of the width of the cutting edge of the chisel should correspond to 40 g of hammer weight, and each millimeter of the width of the cutting edge of the crossmeissel should correspond to 80 g of hammer weight. The weight of a hammer is determined by its size. When choosing the hammer weight, of course, you also need to take into account the age and physical strength working.

Round-faced metalworking hammers are made in six sizes. Hammers weighing 200 g are recommended for instrumental work, as well as for marking and straightening; hammers weighing 400 g, 500 g and 600 g - for metalwork; Hammers weighing 800 g - 1000 g are rarely used, mainly for repair work.

Square-faced locksmith hammers are manufactured in eight sizes: weighing 50 g, 100 g and 200 g - for metalwork and tool work; weighing 400 g, 500 g, 600 g - for metalwork: cutting, bending, riveting, etc. 800 g and 1000 g are rarely used (when performing repair work).

For heavy work, hammers weighing from 4 to 16 kg, called sledgehammers, are used.

The end of the hammer opposite the striker is called the toe. The toe has a wedge shape, rounded at the end. The sock is used when straightening, riveting and

T. D. Striker a - with a square striker; b - applied with a round striker; c - with inserts made of soft measure on the tall chisel; g - wooden (mall); d - dis-

OR KREUTZ - wedging handles

Hammers are made from steel 50 and 40X and tool carbon steel U7 and U8. In the middle part of the hammer there is an oval-shaped hole that serves to attach the handle.

Working parts of the hammer - square or round shape and a wedge-shaped toe - heat-treated to a hardness of НЯС 49-56. Hammer handles are made of hard wood
(dogwood, rowan, oak, maple, hornbeam, ash, birch or synthetic materials).

The handle has an oval cross-section, the ratio of small to large section is 1 1.5, i.e. free

The end is 1.5 times thicker than the end on which the hammer fits.

The end on which the hammer is mounted is wedged with a wooden wedge coated with wood glue, or a metal wedge on which notches (ruffs) are made. The thickness of the wedges in the narrow part is 0.8-1.5 mm, and in the wide part 2.5-6 mm. If the hammer hole has only a lateral expansion, hammer in one longitudinal wedge; if the expansion goes along the hole, then two wedges are driven in (Fig. 38, e) and finally, if the expansion of the hole is directed in all directions, three steel or three wooden wedges are driven in, placing two parallel and the third perpendicular to them. A hammer whose handle forms a right angle with the axis of the hammer is considered to be correctly mounted.

In addition to ordinary steel hammers, in some cases, for example, when assembling machines, so-called soft hammers with inserts made of copper, fiber, lead and aluminum alloys are used (Fig. 38, c). When struck with a soft hammer, the surface of the workpiece material is not damaged. Due to the scarcity of copper, lead and rapid wear, these hammers are expensive to operate. In order to save metal, copper or lead inserts are replaced
rubber, cheaper and more convenient to use. Such a hammer (Fig. 39) consists of a steel body 7, on the cylindrical ends of which caps 2 made of hard rubber are put on. Rubber pads are quite resistant to impacts and can be easily replaced with new ones when worn out. Hammers of this design are used for precision assembly work, especially when it comes to working with parts of low hardness.

In some cases, especially in the manufacture of products from thin sheet iron, wooden hammers(mallets) (see Fig. 38, d).

The operation is called chopping to remove a layer of material from a workpiece, as well as cutting metal (sheet, strip, profile) into pieces with cutting tools (chisel, cross-meisel or groover with a hammer). The processing accuracy when cutting does not exceed 0.7 mm. In modern mechanical engineering, the metal cutting process is resorted to only in cases where the workpiece, for one reason or another, cannot be processed metal cutting machines. Chopping is done following works : removal of excess layers of material from the surfaces of workpieces (cutting off castings, welds, cutting edges for welding, etc.); cutting off edges and burrs on forged and cast workpieces; cutting sheet material into pieces; cutting holes in sheet material; cutting lubrication grooves, etc.

The cutting is done in a vice on a plate or on an anvil. Blanks large sizes When chopping, they are secured in a chair vice. Trimming of castings, welds and bosses in large parts is carried out on site. Manual cutting This is a very difficult and labor-intensive operation, so it is necessary to strive to mechanize it as much as possible.

Tools used in chopping

The tools used for chopping are cutting tools; they are made from carbon tool steels of grades U7, U8, U8A. The hardness of the working part of cutting tools after heat treatment must be at least HRC 53... 56 over a length of 30 mm, and the hardness of the striking part - HRC 30... 35 over a length of 15 mm. The sizes of cutting tools for chopping depend on the nature of the work performed and are selected from the standard range. Hammers are used as impact tools for chopping. various sizes and designs. Most often when chopping, machinist's hammers with a round striker of various weights are used.

The mechanic's chisel (Fig. 2.20) consists of three parts: working, middle, impact. As with any cutting process, the cutting part of the tool is a wedge (Fig. 2.20, a).

The effect of a wedge-shaped tool on the metal being processed varies depending on the position of the wedge and the direction of the force applied to its base. There are two main types of wedge work when cutting:

The axis of the wedge and the direction of the force applied to it are perpendicular to the surface of the workpiece. In this case, the workpiece is cut into pieces (Fig. 2.20, b);

The axis of the wedge and the direction of the force applied to its base form an angle with the workpiece surface that is less than 90°. In this case, chips are removed from the workpiece (Fig. 2.20, c).

The planes limiting the cutting part of the tool (see Fig. 2.20, c) are called surfaces. The surface along which the chips flow during the cutting process is called the front surface, and the surface opposite to it, facing the workpiece surface, is called the back surface. Their intersection forms the cutting edge of the tool. The angle between the surfaces forming the working part of the tool is called the point angle and is denoted by the Greek letter b (beta). The angle between the rake and machined surfaces is called the cutting angle and is designated by the letter 8 (delta). The angle between the rake surface and the plane drawn through the cutting edge perpendicular to the cutting surface is called the rake angle and is denoted by the letter y (gamma).

The angle formed by the back and machined surfaces is called the clearance angle and is designated by the letter a (alpha).

The smaller the sharpening angle of the cutting wedge, the less force must be applied when cutting. However, as the cutting angle decreases, the cross-section of the cutting part of the tool decreases, and therefore its strength. In this regard, the value of the sharpening angle must be selected taking into account the hardness of the material being processed, which determines the cutting force required to separate the metal layer from the surface of the workpiece, and the impact force on the tool necessary to create the cutting force.

With an increase in the hardness of the material, it is necessary to increase the sharpening angle of the cutting wedge, since the impact force on the tool is sufficiently large and its cross-section must provide the cross-sectional area necessary to absorb this force. The values of this angle for various materials are approximately: cast iron and bronze - 70°; medium hard steel - 60°; brass, copper - 45°; aluminum alloys- 35°.

The clearance angle a determines the amount of friction between the rear surface of the tool and the machined surface of the workpiece; its value ranges from 3 to 8. The value of the clearance angle is adjusted by changing the inclination of the chisel relative to the surface being processed.

Kreutzmeisel(Fig. 2.21) differs from a chisel in having a narrower cutting edge. Kreuzmeisel is used for cutting out grooves, cutting keyways and similar work. In order to prevent jamming of the crosspiece during operation, its working part has a gradual narrowing from the cutting edge to the handle. Heat treatment of working and impact parts, as well as geometric parameters cutting part and the procedure for determining the sharpening angles of the cutting part for cross-sections are exactly the same as for a chisel.

Ditcher(Fig. 2.22) is used for cutting out lubrication grooves in liners and bushings of plain bearings and profile grooves special purpose. The cutting edges of the groover can have a straight or semicircular shape, which is selected depending on the profile of the groove being cut. The groover differs from the chisel and crossmeisel only in the shape of the working part. The requirements regarding heat treatment and selection of sharpening angles for groovers are the same as for chisels and cross-cutters.

Locksmith's hammers(Fig. 2.23) are used in chopping as a striking tool to create cutting force and come in two types - with a round (Fig. 2.23, a) and square (Fig. 2.23, b) striker. The end of the hammer opposite the striker is called the toe; it is wedge-shaped and rounded at the end. The hammer is attached to a handle, which is held in the hand during operation, striking the tool (chisel, cross-cutter, groover). To securely hold the hammer on the handle and prevent it from jumping off during operation, wooden or metal wedges (usually one or two wedges) are used, which are driven into the handle (Fig. 2.23, c) where it enters the hole of the hammer.

Cutting small workpieces(up to 150 mm) from sheet material, wide surfaces small-sized steel and cast iron workpieces, as well as cutting grooves in bearing shells, are performed in a vice.

On a plate or anvil, workpieces are cut into pieces or cut along the contour of sheet material workpieces. Chopping on a slab is used in cases where the workpiece being processed is impossible or difficult to secure in a vice.

In order to give the working part of a chisel, crosspiece or groover the required sharpening angle, it must be sharpened.

Sharpening of cutting tools is carried out at sharpening machines(Fig. 2.24, a). The tool to be sharpened is placed on the tool rest 3 and, with light pressure, it is slowly moved across the entire width of the grinding wheel. During the sharpening process, the tool is periodically cooled in water.

Sharpening cutting wedge surfaces lead alternately - first one side, then the other, which ensures uniform sharpening and obtaining correct angle sharpening the working part of the tool. The grinding wheel must be covered with a casing 2 during operation. Eye protection from contact with abrasive dust produced using a special protective screen 1 or safety glasses. Control of the sharpening angle of the cutting tool during the sharpening process is carried out using a special template (Fig. 2.24, b).

Chopping is a metalworking operation in which, with the help of a cutting (chisel, krenzmeisel, etc.) and impact (machinery hammer) tool, excess layers of metal are removed from the surface of a workpiece (part) or the workpiece is cut into pieces.

Felling is carried out in cases where, due to production conditions, machine processing is difficult to perform or irrational and when high precision processing is not required.

Chopping is used to remove (cut down) large irregularities (roughness) from a workpiece, remove hard crust, scale, burrs, sharp corners of edges on cast and stamped parts, for cutting out keyways, lubrication grooves, for cutting cracks in parts for welding (cutting edges ), cutting off the heads of rivets when removing them, cutting holes in sheet material. In addition, chopping is used when it is necessary to chop off some part from rod, strip or sheet material.

The workpiece is secured in a vice before cutting. Large workpieces are chopped on a slab or anvil, and especially large ones - at the place where they are located.

Depending on the purpose of the workpiece, cutting can be finishing or roughing. In the first case, a chisel removes a layer of metal with a thickness of 0.5 to 1 mm in one working stroke, in the second - from 1.5 to 2 mm. The processing accuracy achieved during cutting is 0.4...1 mm.

When cutting, as in most metalworking operations (filing, drilling, scraping, lapping, etc.), cutting is carried out - the process of removing an excess layer of metal in the form of chips from the workpiece (part) with a cutting tool.

The cutting part of any cutting tool is a wedge with certain angles. Chisel, cutter one wedge, hacksaw blade, tap, die, cutter, file several wedges.

Working tools/angles, chisel sharpening techniques, etc.

Any cutting tool becomes dull sooner or later during use. If it is “disposable”, it has one way - to the landfill. If the instrument can really be restored, why not take advantage of this opportunity?

Let's clarify the terminology. The cutting edge of a tool is formed by two converging planes (or curves, like drills). The sharpening angle is the angle at the apex of convergence of these planes. The sharpness of an edge can be represented as the reciprocal of the width of the “platform” at the top or the diameter of the circle inscribed in it. In practice, the smoother the converging surfaces, the sharper the RO will be. Sharpening angles different instruments vary and depending on the quality of the steel and the material being cut are: for a chisel – 17–25 degrees, for a plane iron – 25–40, for a chisel – 30–40, for a metal chisel – up to 60, for scissors – 45–60, for knives – 20–30 degrees.

Sharpening turning tools

Turning cutters are sharpened on the front and back surfaces. There is only one nuance - the cutter tapers downwards, therefore, so that its side planes in no case come into contact with the workpiece, contact should only be along the cutting edge.

Quick-cutting and carbide-tipped cutters are sharpened to grinding wheel. If the machine does not have a water supply, frequently dip the cutter in a container of water.

Drill sharpening

When sharpening a drill, you need to hold it so as to obtain the desired angle of convergence of the cutting edges. In this case, the cutting edge must be symmetrical.

The easiest way is to draw a line on the tool tool with a felt-tip pen and hold the drill parallel to it. However, simply placing the drill along the line is not enough; you should also turn it desired angle around the axis, and then 180 degrees relative to the first position.

An angle is needed between the edge of the drill and the plane of the table, that is, the outer edge must be below the center, otherwise the drill will not cut the material, but will ride along it with its back surface. To control this angle there is various devices, but it’s easier to stand or sit at a table so that the glare from the lighting is on the outer part of the cutting edge, and then, without changing your body position, turn the drill in your fingers and catch the glare again - the edges will be sharpened at the same angle.

Drill sharpening on the back surface is called single, with it there remains a rather large jumper in the center, which does not cut, but scrapes the metal. If you sharpen it, the drilling speed will increase. There are many ways to sharpen a jumper. In factories it is sharpened with thin abrasive or diamond wheels or on the corner of a wide stone. But you can sharpen the jumper as shown in the photo. Safety glasses are strictly required when sharpening.

Sharpening chisels

This tool is a metal rod, one end of which (the striker) has the shape of a truncated cone with a semicircular base, and the other (the blade) is a wedge. Both ends are quenched and tempered.

The chisel is used for metal processing. Its length is approximately 100–200 mm, blade width is 5–52 mm. The blade of the tool must be well sharpened, since the force of the impact depends on this (the sharper the blade, the less force is applied during impact).

The sharpening angle of the chisel blade is different. A blade with an obtuse sharpening angle works with hard metals. It should be taken into account that medium-hard steel is processed with a blade with a sharpening angle of at least 60°; cast iron, bronze, hard steel – 70°.

A smaller sharpening angle for the chisel blade is required when working with soft metals, such as copper and brass. The sharpening angle of the blade should be approximately 45°. Zinc and aluminum are processed with a chisel whose blade sharpening angle is 35°.

The tool blade is sharpened at sharpening machine. The grit size of the electrocorundum wheels should be 40, 50 or 63.

To control the sharpening angle of the chisel, a special template is used, which is a metal block on which 4 grooves with angles of different sizes are cut (Fig. 1).

Rice. 1. Template for checking the sharpening angle of the chisel

When working with a chisel, it should be taken into account that for pipes made of gray cast iron coated with bitumen, it is recommended to use an ordinary chisel. Pipes with outer surface a layer of hard white cast iron is cut with a chisel with a carbide insert.