Cutting is called an operation for removing a layer of material from the workpiece, as well as cutting metal (sheet, strip, profile) into pieces with cutting tools (chisel, cross-meisel or groover with a hammer). Processing accuracy during felling does not exceed 0.7 mm. In modern mechanical engineering, metal cutting is resorted to only in those cases when the workpiece, for one reason or another, cannot be processed on metal-cutting machines. Cutting perform following works : removal of excess layers of material from the surfaces of workpieces (cutting off castings, welds, cutting edges for welding, etc.); trimming edges and burrs on forged and cast blanks; cutting into pieces of sheet material; punching holes in sheet material; cutting oil grooves, etc.

Cutting is carried out in a vise on a plate or on an anvil. Blanks large sizes when cutting, they are fixed in a chair vice. The trimming of castings, welds and bosses in large parts is carried out on site. Manual cutting is a very difficult and time-consuming operation, so it is necessary to strive to mechanize it as much as possible.

Cutting tools

The tools used in cutting are cutting tools; they are made of carbon tool steel grades U7, U8, U8A. The hardness of the working part of the cutting tools after heat treatment should be at least HRC 53 ... 56 for a length of 30 mm, and the impact part - HRC 30 ... 35 for a length of 15 mm. The dimensions of cutting tools for cutting depend on the nature of the work performed and are selected from the standard range. As percussion instrument hammers are used for cutting various sizes and designs. Most often, when cutting, metalwork hammers with a round head of various weights are used.

The locksmith's chisel (fig. 2.20) consists of three parts: working, middle, shock. As with any cutting, 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 operation during 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 less than 90° with the workpiece surface. In this case, chips are removed from the workpiece (Fig. 2.20, c).

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

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

The smaller the angle of sharpening of the cutting wedge, the less force must be applied when cutting. However, with a decrease in the cutting angle, the cross section of the cutting part of the tool also decreases, and hence its strength. In this regard, the value of the taper angle must be chosen 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 a cutting force.

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

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

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

ditcher(Fig. 2.22) is used for cutting lubrication grooves in bushings 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 ditcher differs from the chisel and the crosscut only in the shape of the working part. The requirements for heat treatment and the choice of sharpening angles for groovers are the same as for chisels and crosscuts.

Locksmith hammers(Fig. 2.23) are used when cutting as a percussion tool to create a cutting force and are of 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 has a wedge-shaped shape and is rounded at the end. The hammer is fixed on the 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 hammered into the handle (Fig. 2.23, c) where it enters the hammer hole.

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

On a plate or anvil, workpieces are chopped into pieces or cut out along the contour of workpieces from sheet material. Cutting on a plate is used in cases where it is impossible or difficult to fix the workpiece in a vice.

In order to give the working part of a chisel, crosscut or groover the necessary sharpening angle, it is necessary to sharpen it.

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

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

felling is an operation in which, with the help of a chisel and a metal hammer, layers of metal are removed from the workpiece or the workpiece is cut.

The physical basis of cutting is the action of a wedge, the shape of which is the working (cutting) part of the chisel. Cutting is used in cases where the machining of workpieces is difficult or irrational.

With the help of cutting, metal irregularities are removed (cut down) from the workpiece, hard crust, scale, sharp edges of the part are removed, grooves and grooves are cut, and sheet metal is cut into pieces.

Cutting is usually done in a vise. The cutting of the sheet material into pieces can be carried out on the plate.

The main working (cutting) tool during cutting is a chisel, and a hammer is a percussion tool.

Cold chisel (Figure 8) is made of U7A or U8A carbon tool steel. It consists of three parts: shock, middle and working. shock part 1 it is performed tapering upwards, and its top (the striker) is rounded; for the middle part 2 the chisel is held during cutting; working (cutting) part 3 has a wedge shape.

Figure 8 Bench chisel

The angle of sharpening is selected depending on the hardness of the material being processed. For the most common materials, the following taper angles are recommended:

For hard materials (solid steel, cast iron) - 70 °;

For medium hard materials (steel) - 60°;

For soft materials (copper, brass) - 45°;

For aluminum alloys - 35°.

Kreutzmeisel - a chisel with a narrow cutting edge (Figure 10), designed for cutting narrow grooves, keyways of low accuracy and cutting rivet heads. Such a chisel can also be used to remove wide layers of metal: first, grooves are cut with a narrow chisel, and the remaining protrusions are cut down with a wide chisel.

Locksmith hammers , used in metal cutting are of two types: with round and with square briskly. The main characteristic of a hammer is its mass.

Hammers with a round face are numbered : 1st to 6th . Nominal weight of hammer No. 1 - 200 g; No. 2 - 400 g; No. 3 - 500 g; No. 4 - 600 g; No. 5 - 800 g; No. 6 - 1000 g. Square hammers are numbered from 1 to 8 and weight from 50 to 1000 g.

Hammers material - steel 50 (not lower) or U7 steel.

The working ends of the hammers are heat treated to hardness HRC 49-56 for a length equal to 1/5 of the total length of the hammer from both ends.

For locksmith work, hammers with a round striker No. 2 and 3, with a square striker No. 4 and 5 are used. The length of the hammer handle is approximately 300-350 mm.

3.4 Metal cutting

Cutting - plumbing operation to separate the whole piece(blanks, parts) into parts. It is carried out without chip removal: with wire cutters, scissors and pipe cutters and with chip removal: with hacksaws, saws, cutters and special methods (gas cutting, anode-mechanical and electric spark cutting, plasma cutting).

The wire is cut with needle nose pliers (nippers), sheet material - with scissors; round, square, hexagonal and strip material of small sections - with hand saws, and large sections on cutting machines with hacksaw blades, circular saw blades, special methods.

The essence of the operation of cutting metal with needle nose pliers (nippers) and scissors is to separate the wire, sheet or strip metal on parts under pressure of two wedges (cutting knives) moving towards each other.

Pliers cut (bite off) round steel parts and wire. They are made with a length of 125 and 150 mm (for cutting off wire with a diameter of up to 2 mm) and a length of 175 and 200 mm (for diameters up to 3 mm).

The cutting edges of the jaws are straight and sharpened at an angle of 55-60°. Cutters are made from U7, U8 carbon tool steel or steel 60-70. Sponges are thermally processed to hardness HRC 52-60.

Hand scissors designed for cutting sheet mild steel, brass, aluminum and other metals. They are made in lengths of 200 and 250 mm for cutting metal with a thickness of up to 0.5 mm, 320 mm (for a thickness of up to 0.75 mm), 400 mm (for a thickness of up to 1 mm).

The material of the scissors is steel 65, 70. The scissor blades are heat-treated to a hardness of HRC 52-58. The cutting edges of the blades are sharply sharpened at an angle of 70°. The blades of the scissors in the closed state mutually overlap, and the overlap at the ends does not exceed 2 mm.

Chair scissors cut sheet metal up to 3-5 mm thick. One of the handles of the scissors is bent at an angle of 90° and is rigidly attached to a table or other base. The length of the working handle of the scissors is 400-800 mm, the cutting part is 100-300 mm.

Lever scissors used for cutting sheet metal up to 5 mm thick. The scissors are made from U8A tool steel and heat treated to a hardness of HRC 52-58. The angle of sharpening of the cutting edges of the knives is 75-85°.

Pipe cutters Designed for manual cutting of thin-walled (gas) pipes made of mild steel, cutting is performed without removing chips. They are available in two sizes: for cutting pipes from 1/2 to 2" and for pipes - from 1 to 3".

The main parts of the pipe cutter are rollers: one cutting (working) and two guides. The pipe is cut by a working roller; at the same time, it is fixed on guide rollers and tightened with a screw.

Hand saw (Figure 9, a) is used for cutting relatively thick sheets of metal and round or shaped rolled products. A hacksaw can also be used to cut slots, grooves, trim and cut blanks along the contour, and other work. They are made from U8-U12 or 9XC steels with the hardness of the cutting part HRC 58-61, the core - HRC 40-45. It consists of a frame 1 , tension screw with wing nut 2, handles 6, hacksaw blade 4, which is inserted into the slots of the heads 3 and fastened with pins 5.

Figure 9 Hand saw a - device, b - sharpening angles, c - tooth setting "on the tooth", d - tooth setting "on the canvas".

Each tooth of the blade has the shape of a wedge (cutter). On it, as well as on the incisor, a rear angle is distinguished α, taper angle β , rake angle γ and cutting angle δ= α + β (Figure 9, b). When notching the teeth, it is taken into account that the resulting chips must be placed between the teeth before they exit the cut. Depending on the hardness of the materials being cut, the blade tooth angles can be: γ = 0-12°, β = 43-60° and α = 35-40°. So that the width of the cut made with a hacksaw is slightly larger web thickness, carry out the setting of the teeth “on the tooth” (Figure 9, in) or “along the canvas” (Figure 9, G). This prevents the blade from jamming and makes work easier.

Cutting is an operation in which, with the help of a chisel and a metalwork hammer, layers of metal are removed from the workpiece or the workpiece is cut.

Physical basis cutting is the action of a wedge, the shape of which is the working (cutting) part of the chisel. Cutting is used in cases where the machining of workpieces is difficult or irrational.

With the help of cutting, metal irregularities are removed (cut down) from the workpiece, hard crust, scale, sharp edges of the part are removed, grooves and grooves are cut, and sheet metal is cut into pieces.

Cutting is usually done in a vise. Cutting sheet material into parts - can be performed on a plate.

The main working (cutting) tool during cutting is a chisel, and a hammer is a percussion tool.

The bench chisel (11) is made of tool carbon steel. It consists of three parts: shock, middle and working. The shock part / is made tapering upwards, and its top (the striker) is rounded; for the middle part 2, the chisel is held during cutting; working (cutting) part 3 has a wedge shape. The angle of sharpening is selected depending on the hardness of the material being processed.

For the most common materials, the following taper angles are recommended: for hard materials(hard steel, cast iron) - 70°; for materials of medium hardness (steel) ~ 60°; for soft materials(copper, brass) "- 45 °; for aluminum alloys- 35°.

The working and impact parts of the chisel are subjected to heat treatment (hardening and tempering). The degree of hardening of the chisel can be determined by running a file over the hardened part of the chisel: if the file does not remove chips, but slides over the surface, the hardening is done well.

To cut out narrow grooves and grooves, a chisel with a narrow cutting edge is used - a cross-cutting tool. Such a chisel can also be used to remove wide layers of metal: first, grooves are cut with a narrow chisel, and the remaining protrusions are cut down with a wide chisel.

For cutting out profile grooves (semicircular, dihedral, etc.), special crosscut groovers are used, which differ only in the shape of the cutting edge.

Bench hammers used in cutting metals are of two types: with a round and with a square head. The main characteristic of a hammer is its mass. For cutting metals, hammers weighing from 400 to 600 g are used.

The cutting of metals is a very labor-intensive operation. To facilitate labor and increase its productivity, mechanized tools are used. Among them most widespread has a pneumatic chipping hammer (12) It is driven by compressed air, which is supplied through hose 3 from a permanent pneumatic network or a mobile compressor. When chopping metal, the trigger 2 is pressed, squeezing the spool 4. Air, entering through the air channels, moves the striker 6, which strikes the shank of the chisel 7 inserted into the barrel 5. During cutting, the pneumatic chipping hammer is held with both hands: with the right - by the left handle - behind the end of the trunk, and guide the chisel along the cutting line.

Cutting is a locksmith operation in which, with the help of a cutting tool (chisel, crosscut or groover) and a percussion tool (locksmith's hammer) with. workpieces or parts are removed excess metal layers or the workpiece is cut into pieces.

Cutting is carried out in cases where it is not required high precision processing. The processing accuracy achieved during felling is 0.4-0.7 mm.

Cutting is used to remove (cut off) large irregularities (roughness) from the workpiece, remove hard crusts, scale, burrs, sharp corners of edges on cast and stamped parts, for cutting keyways, lubrication grooves, for cutting cracks in parts for welding (cutting edges ), cutting off rivet heads when they are removed, punching holes in sheet material.

In addition, cutting is used when it is necessary to chop off some part from a bar, strip or sheet material.

Cutting is carried out in a vice, on a plate or on an anvil. Billets and castings of small sizes during cutting are fixed in a chair vise. Pruning of defects in welds and tides in large parts is carried out on site.

Cutting metal with a hand chisel is a very time-consuming and difficult operation. Therefore, it is necessary to strive to mechanize it as much as possible.

The means of mechanization of metal cutting are: replacement of cutting by processing with an abrasive tool, as well as replacement of a manual chisel with a pneumatic or electric chipping hammer.

Starting cutting, the mechanic must prepare his workplace. Having taken a chisel and a hammer from the workbench box, he places the chisel on the workbench on the left side of the vise with the cutting edge towards him, and the hammer - with right side vise with a striker directed towards the vise.

Of great importance for felling is the correct position of the locksmith's body. When chopping, it is necessary to stand at the vise steadily, half-turned to them; the body of the worker must be to the left of the vise axis. Put the left leg half a step forward so that the axis of the foot is at an angle of 70-75 ° in relation to the vise. Move the right leg back a little, turning the foot at an angle of 40-45 ° with respect to the axis of the vise.

The hammer must be taken by the handle so that the hand is at a distance of 20-30 mm from the end of the handle (Fig. 32, a). The handle is clasped with four fingers and pressed to the palm; at the same time, the thumb is placed on the index finger and all fingers are tightly squeezed. Hold the chisel with your left hand, without squeezing your fingers strongly, at a distance of 20-30 mm from the head (Fig. 32, b).

In the process of cutting, the chisel should be directed at an angle of 30-35 ° with respect to the surface being processed (Fig. Fig. 33, a). With a smaller angle of inclination, it will slide, and not cut (Fig. 33, b), and with a larger one, it will unnecessarily go deep into the metal and give large processing irregularities (Fig. 33, d).

Essential to the process manual felling in a vice has also correct installation chisels in relation to vertical plane fixed jaw vise. The normal setting of the cutting edge of the chisel should be considered an angle of 40-45 ° (Fig. 34, a). At a smaller angle, the cut area increases, the cutting becomes harder, and its process slows down (Fig. 34, b). At a larger angle, the chips, curling,

Creates additional resistance to the cut, the cut surface is rough and torn; it is possible to shift the workpiece in a vice (Fig. 34, c).

The quality of cutting depends on the type of swing and hammer blow. There are carpal, elbow and shoulder blows. With a wrist swing, hammer blows are made with the power of the hand. Such a blow is used in light work to remove thin chips or to remove small irregularities. With an elbow strike, the arm bends at the elbow, the blow is stronger. Elbow strike is used in conventional felling, when it is necessary to remove a layer of metal of medium thickness, or when cutting grooves and grooves. With a shoulder strike, the swing is the largest, and the blow is the strongest. A shoulder strike is used when cutting thick metal, when removing large layers in one pass, cutting metal and processing large planes.

When cutting with the use of a brush stroke, an average of 40-50 strokes per minute is used; with harder work and shoulder impact, the cutting rate is reduced to 30-35 beats per minute.

The blow of the hammer on the chisel should be as precise as possible. It is necessary that the center of the hammer striker falls into the center of the chisel head, and the hammer handle with the chisel forms a right angle. You can only cut with a sharply sharpened chisel; a blunt chisel slips off the surface, the hand quickly gets tired of this and, as a result, the correctness of the blow is lost.

The size of the chip removed by the chisel depends on physical strength working, chisel size, hammer weight and hardness of the metal being processed. Cutting is considered the most productive, in which a layer of metal 1.5-2 mm thick is removed in one pass. When removing a thicker layer, the locksmith quickly gets tired, and the cutting surface is unclean.

The cutting of brittle metals (cast iron, bronze) should be carried out from the edge to the middle of the workpiece in order to avoid chipping off the edge of the part. When cutting viscous metals ( mild steel, copper, brass) it is recommended to periodically moisten the cutting edge of the chisel engine oil or soapy emulsion.

Cutting in a vice can be performed at the level of the vise jaws or above this level - according to the marked risks. Thin metal is most often cut at the level of the vise jaws, and wide surfaces of the workpiece are cut above the level.

When chopping wide surfaces, to reduce the time, you should use a crosscut - a mudflow and a chisel. First, the grooves are cut through with a crosscut, and then the protrusions formed are cut down with a chisel.

In order to perform cutting correctly, you need to have a good command of the chisel and hammer, i.e., hold the chisel and hammer correctly, without misses and correctly swing and hit the chisel head with a hammer.

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Details Category: Long products

metal cutting

felling divide the workpiece into parts, remove excess metal ( allowance), make lubrication grooves in the details, etc. This operation is carried out using chisels (fig. right) and a hammer.

cutting part chisel, like any other cutting tool, has the shape wedge .

Tapering angle (sharpening) depends on the hardness of the metal being processed: the harder the metal, the greater the sharpening angle should be. For steel, an angle of 60° is recommended, for non-ferrous metals - 35° ... 40°.

A special chisel is used to cut grooves - kreuzmeisel(fig. right).

When cutting, hammers weighing 400 or 500 g are used.

Before cutting, the workpiece is fixed in a vise 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 are applied to the chisel with a hammer different strength.
Distinguish carpal , ulnar and shoulder punch ( see fig. below).

Kistev (rice. a) with a blow remove small irregularities and thin chips, ulnar (rice. b) - cut off excess metal and cut into pieces the workpiece is not thick. At carpal On impact, the hammer moves due to the movement of the hand.
At elbow on impact, the arm bends at the elbow and the impact becomes stronger (Fig. b). Loktev the excess metal is cut off with a blow and the blanks are divided into parts.
Shoulder blow (Fig. in) - cut down thick chips, cut bars, strips of great thickness.

In cases where the workpiece cannot be fixed in a vice, it is processed on stove(fig. 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 punching a workpiece 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 good 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 carried out locksmiths by 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 are used in recent times, it should be noted oxygen, laser, etc. These installations serve metal cutters.

A variety of chisels and crosscuts are shown in the figure below.