Modern methods of metal cutting and its defects. Percussion instruments Device for chopping metal
Metal cutting
CUTTING is a metalworking operation in which a layer of metal is removed from the surface of a workpiece using cutting and impact tools or the workpiece is divided into parts.
Chopping is a rough, preliminary operation. It is intended to prepare the workpiece for subsequent processing.
Chopping is used to remove large irregularities, burrs, sharp edges from workpieces, cutting out grooves and grooves, cutting out holes in sheet material.
A layer of metal up to 2 mm can be removed in one pass. The processing accuracy is 0.5-1 mm.
The cutting tool for chopping is a chisel and cross-cutting tool, and the striking tool is a hammer.
The shape of the cutting part of any cutting tool is a wedge. The force that must be applied, the strength of the tool and the size of the metal layer to be removed depend on how sharp the wedge is and how it is installed in relation to the workpiece being processed.
Chisel consists of working, middle and shock parts. The working part is sharpened, forming a cutting part with cutting edge.
The chisel is made with a length of 100; 125; 160; 200 mm and the width of the working part, respectively, 5; 10; 16: 20 mm.
Kreutzmeisel has the same elements as the chisel. It features a narrower cutting edge and the shape of the working part. Designed for cutting grooves and grooves. Cutting edge width 2; 5; 8; 10; 12 mm.
Ditcher- a type of cross-cutting machine with a rounded cutting edge for cutting out grooves of complex profiles. Made in length 80; 100; 120; 150; 200; 300; 350 mm with cutting edge radius 1; 1.5; 2.0; 2.5: 3.0 mm.
There are two types of locksmith's hammers: square-faced hammers and round-faced hammers.
The hammer consists of a hammer and a handle. The main characteristic of a hammer is its mass. Hammer handles are made of hardwood (birch, oak)
For hard work use hammers weighing 4-16 kg - sledgehammers. In addition to hammers with steel strikers, when assembling and repairing mechanisms and machines, hammers with inserts made of soft metals (copper, aluminum, lead), as well as wooden hammers with round and rectangular strikers are used.
Sharpening of cutting tools is done manually at sharpening machines. The following cutting angles are recommended:
Hard materials (cast iron) 70 degrees
Medium hardness (steel) 60 degrees
Soft (brass, copper) 45 degrees
Aluminum alloys 35 degrees
The sharpening angles are controlled by the template.
Chopping is carried out in a vice, on plates, and anvils.
When chopping in a parallel vice, apply blows in the direction of the stationary jaw. To accurately strike a cutting tool with a hammer, the worker’s body must be turned half a turn to the axis of the vice. The weight of the hammer is selected depending on the width of the cutting part of the chisel and the thickness of the removed layer of metal, usually calculated at the rate of 40 g per 1 mm of the width of the chisel blade and 80 g per 1 mm of the width of the crossmeissel blade.
The metal is cut on a plate with a chisel in a vertical position and a shoulder blow with a hammer. Strip and sheet metal up to 2 mm thick are cut through with one blow, more than 2 mm are cut through approximately half the thickness on both sides, and then broken, bent in one direction or the other.
The blanks are cut down after marking, retreating from the marking line by 2-3mm. After hitting with a hammer, the chisel is moved along the cutting line at a distance less than the width of its cutting part. This results in a smooth groove without steps. When cutting sheet metal and strip metal, the workpiece is clamped so that marking line coincided with the level of the sponges.
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
Cutting technology involves cutting off excess metal parts using special tools. It is 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 to remove burrs and divide the source material into parts. 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 sharp corner during 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. Hammers are used as percussion instruments. 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. A brush blow is used to separate thin chips and remove small 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 horizontally on the work surface, and the tool 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 of mild steel under the workpiece. 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 does not require any additional processing after cutting. 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. Suitable for thin sheets (approx. 1 mm) manual equipment. The 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 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 big amount electronics. This allows you to cut metal blanks in an almost fully automatic mode.
Metal cutting, tools and technological features which we will consider in this article is enough labor-intensive process, which requires not only compliance with safety precautions, but also special human control.
Today there is a huge number various instruments for cutting metal, as well as other auxiliary means for cutting it. In this case, we will have to familiarize ourselves in detail with the procedure for cutting metal and consider with the help of what tools it is performed.
Main purposes
Basically, a procedure such as cutting metal on a guillotine or other machine and device is used in the following cases:
- Cutting down or removing excess layers of metal from the surface of workpiece parts.
- Leveling surfaces that have an uneven shape.
- The procedure for removing hard crust and scale.
- Cutting off burrs and other irregularities on forged and cast parts.
- Trimming excess material, its ends, edges and individual sheets.
- Cutting metal into pieces using a guillotine (for sheet and long material).
- Making holes marked with a specific contour.
- Cutting edges end to end for welding.
- Chopping off the heads of rivets and subsequently removing them.
- Cutting out lubrication channels and keyways.
In this case, the most popular machine is the guillotine, which uses high pressure to cut the material with a sharp movement. Chopping sheet metal guillotine is also possible, but it requires higher pressure compared to small parts and workpieces.
As mentioned above, guillotines are mainly used for cutting metal, but plasma cutting has not yet been canceled. In this case, we will consider the pros and cons of each option separately.
Cutting and bending metal using a guillotine
Guillotines are not that expensive and have a lot of advantages, namely:
- Quick slicing metal parts and removing excess from workpieces.
- Guillotines are easy to use and do not pose any danger to humans when used correctly.
- Currently, there are mechanisms that allow not only chopping, but also bending metal, giving it different shapes.
- Bending sheet metal is possible even when using a compact guillotine.
- It is quite easy to repair the machine yourself due to the fact that there are no complex mechanisms.
- Guillotines are well suited for cutting small holes and channels.
However, these machines also have disadvantages, namely:
- They have a large mass, which in some cases complicates their use.
- The pressure created when cutting metal is carried out by air, which requires a constant connection to a compressor.
- The price of a good guillotine is quite high, but this guarantees its long service life and the quality of processing of the metal that was bent on it.
- Like bending machine Although it is easy to repair and maintain, it does require the selection of special parts.
Against the backdrop of the huge number of advantages of guillotines, a small list of their disadvantages looks insignificant.
Plasma cutting
This auxiliary method of cutting metal has the following qualities:
- quickly, smoothly and efficiently cuts metal of any thickness;
- has compact dimensions;
- ease of use.
Despite the small list of advantages, plasma cutting has a lot of disadvantages, namely:
- Unsafe at work.
- Requires constant connection to oxygen cylinders;
- When using, you must carefully monitor the temperature, otherwise there is a risk of explosion.
- Working with plasma cutting requires the use of a protective helmet or lenses, as high temperature and a bright spark can make a person go blind.
- With its help you can only cut metal; it is impossible to bend or make channels in it.
Plasma cutting still has many disadvantages, but it is valued for its speed. With its help, you can cut sheet metal to size in a matter of minutes.
Metal bending
Bending is a process in which metal is pressed high pressure crank press accepts curved shape. In this case, the use of guillotine equipment is provided, which, in addition to cutting, is also capable of bending metal under high pressure.
Thus, a striking example of bending guillotines and their work is the production of rectangular ventilation systems, as well as many other parts, which are subsequently connected using rivets, forming a single air-ventilation system.
Important. Equipment for cutting, chopping and bending metal requires appropriate maintenance and repair. That is why, after purchasing, it is recommended to choose a workshop that provides the appropriate services.
Purchase of equipment and its further maintenance
Services for the purchase of equipment for cutting and processing rolled metal are provided by large machine-building plants where machines with guillotine and other functions are produced. They can be found on the Internet on the official resources of manufacturers in Moscow, Novosibirsk, Chelyabinsk and many other cities of Russia.
Machine maintenance is carried out both by the manufacturers themselves and by third-party companies whose activities are aimed at servicing and repairing large metal rolling equipment. You can also find such services on the Internet or by requesting recommendations from the equipment manufacturer.
Video: cutting metal with a guillotine.
Results
IN modern life metalworking has undergone a number of innovative changes, automated guillotines and other machines have appeared that, with a correctly specified program, are capable of producing a workpiece without flaws.
Subsequently, this part does not need to be additional processing and it can be sent to the buyer immediately. Of course, a number individual cases requires direct human control and intervention, but the main work is performed by the equipment using a given program.
Metalworking will always be in demand, due to the fact that this material is used everywhere. That is why guillotines and other equipment are manufactured with the expectation that they will last for decades. But this is only possible if the machines are regularly repaired and maintained.
K category: Locksmith work
Metal cutting
At modern methods processing of material or workpieces, metal cutting is an auxiliary operation. It is used in cases where low processing accuracy is required hand tools divide the metal into parts for blanks, remove thick layer metal, eliminate irregularities and tides on forgings and castings, remove the hard crust, cut a groove.
Metal cutting is carried out in a vice, on a plate and on an anvil using a metalworker's hammer, a chisel, a cross-cutting tool, a blacksmith's chisel and a sledgehammer.
Metal cutting can be horizontal or vertical depending on the location of the chisel during the operation. Horizontal cutting is done in a vice. In this case, the rear edge of the chisel is installed to the plane of the vise jaws at an angle of no more than 5°.
Vertical cutting is done on a slab or anvil.
The chisel is installed vertically, and the material to be cut is laid horizontally on the slab.
Rice. 1. Parallel vice: 1 - worm screw, movable jaw, 5 - fixed jaw, 4 - turntable, 5 - turntable screw, 6 - bottom plate, 7 - nut
There are parallel vices (Fig. 1) - cast iron with steel hardened overhead jaws and chair vices (Fig. 2) - steel. The material is cut mainly in a chair vice, since they are stronger than parallel ones. Only thin steel can be cut using a parallel vice.
Chopping of thin metal, chopping of planes, bosses, burrs, cutting of grooves is carried out in a vice, and chopping of thick metal or long strips and rods -on the stove or anvil.
The machinist's hammers used for chopping come with round or square strikers (Fig. 3, a, b).
Rice. 2. Chair vice: 1-lever, 2-washer, 3-screw, 4-casing
The working parts of the hammer are hardened and tempered. The hammer must be in good condition, without cracks, caps, cavities and other defects.
For metal cutting, hammers weighing 500, 600 and 800 g are used. Hammers are mounted on handles made of hard and tough wood (birch, maple, oak, rowan). Handles should have an oval shape, a smooth and clean surface, without knots or cracks. The length of the handle of a hammer weighing 500-600 g is 350 mm, and that weighing 800 g is 380-450 mm.
Rice. 3. Tools for bench cutting: a - a mechanic’s hammer with a round striker, b - a mechanic’s hammer with a square striker, c - a chisel, d - a crosspiece
To prevent the hammer from jumping off during operation, the end of the handle on which the hammer is mounted is wedged with wooden or metal wedges 1-3 mm thick. The wedges are placed along the major axis of the handle section. Wooden wedges are placed on glue, and metal ones are roughed up so that they do not fall out.
The working part of the chisel and the crosspiece is hardened to a length of at least 30 mm, and the head is hardened weaker than the blade (about 15-25 mm in length) so that when struck with a hammer it does not crumble or crack. The rest of the chisel and crosspiece should remain soft.
Chisels and crosspieces should not have cracks, caps or other defects.
The most commonly used chisels are 175 and 200 mm long with blades 20 and 25 mm wide. To cut grooves in steel and cast iron, cross-cutting tools 150-175 mm long with a blade 5-10 mm wide are used.
The heads of the chisel and crosspiece are forged to a cone, which ensures the correct direction of the hammer blow and reduces the possibility of a mushroom cap forming on the head.
Chisels with a blade width of 20 mm have a head measuring 12X12 mm, length 18 mm; with a blade 25-16×28 mm, length 20 mm. Crosspieces with a 5 mm wide blade have a head measuring 8X14 mm, 12 mm long and with a 10 mm blade - 12X28 mm, 15 mm long.
The sharpening angle of chisels and crossbars depends on the hardness of the metal being processed. For chopping cast iron, hard steel and hard bronze, the sharpening angle of the tool is 70°, for chopping medium and soft steel - 60°, for chopping brass, copper and zinc - 45°, for chopping very soft metals (aluminum, lead) -35- 45°.
Rice. 4. Sharpening a chisel on a sharpening machine: a - techniques for holding the chisel when sharpening, b - a template for checking the correct sharpening angle
Locksmith tool sharpened on sharpening machines with abrasive wheels. During sharpening, the working part of the tool (blade) becomes very hot and may become loose. During tempering, the hardness of the hardening is lost and the tool becomes unsuitable for further work. To avoid this, the working part of the tool is cooled with water during sharpening.
In Fig. Figure 6 shows how to hold the chisel when sharpening and check that the angle is sharpened correctly. The productivity and cleanliness of metal cutting depend on correct techniques work.
When chopping, you need to stand steadily and straight, half-turned towards the vice. The hammer is supposed to be held by the handle at a distance of 15-20 mm from the end and applied strong blows to the center of the chisel head. You should look at the chisel blade, not at its head, otherwise the chisel blade will not go properly.
The chisel should be kept at a distance of 20-25 mm from the head.
In Fig. Figure 5 shows the correct position of the body and legs of the worker, as well as how to hold the hammer and chisel.
Metal cutting in a vice is done as follows. Workpieces made of sheet or section steel can be cut in a vice at the level of the jaws or at marks above the level of the jaws of the vice.
Rice. 5. The position of the worker’s body and legs at the vice when chopping and techniques for gripping the tool: a - elbow swing, b - shoulder swing
When chopping at the level of the jaws of the vice, the workpiece is clamped firmly in the vice so that the upper edge protrudes above the jaws by 3-4 mm and the first chips are cut down along the entire length of the workpiece. Then the workpiece is rearranged in a vice so that the upper edge protrudes 3-4 mm above the level of the vice jaws, and the second chip is cut off. This is how the product is sequentially cut to the required size.
When cutting above the level of the vise jaws along the marks, the workpiece is clamped in the vice so that the marked mark is above the level of the vice jaws and parallel to them. The cutting is carried out according to the marked marks sequentially, as when cutting according to the level of the jaws of the vice. When chopping, the chisel blade should be positioned at an angle of 45° to the metal being cut, and the head should be raised upward at an angle of -25-40°, as shown in Fig. 6. With this arrangement of the chisel, the cutting line will be smooth and cutting will be done faster.
A large layer of metal on a wide plane of the workpiece is cut down as follows: the workpiece is clamped in a vice, a chamfer is cut off with a chisel, transverse grooves are cut with a cross-section, and then the protruding edges are cut off with a chisel.
When cutting grooves with a cross-section, the thickness of the chips should be no more than 1 mm, and when cutting off protruding edges with a chisel - from 1 to 2 mm.
Strip steel is cut on a plate or anvil (Fig. 7). First, cut lines are drawn on both sides of the strip with chalk. Then, having laid the strip on the anvil, set the chisel vertically on the marked mark and, with strong blows of the bench hammer, cut the strip to half its thickness.
Then the strip is turned over, cut on the other side and the part to be cut off is broken off.
Round metal is cut in the same way, with the rod turning after each blow. Having cut the rod along the entire circumference to a sufficient depth, break off the part to be cut off.
Metal made of carbon and alloy structural steel with a thickness of up to 20-25 mm can be cut in a cold state on a plate or anvil using forge chisels and sledgehammers (Fig. 6, a, b, c, d).
Rice. 6. The location of the chisel when cutting in a vice: a - at the level of the vice jaws (front view), b - the same (top view), c - above the level of the vice
Rice. 7. Techniques for cutting strip steel on an anvil (vertical cutting)
To do this, cut lines are drawn with chalk on two or four sides of the workpiece. Then the metal is laid on the anvil, the forging chisel is installed vertically on the marking line and the metal is cut along this entire line to the required depth with strong blows of the sledgehammer, gradually moving the chisel. The metal is also cut on the other side or on all four sides, after which the part to be cut off is broken off.
To speed up and simplify cutting, use auxiliary tool-lower (sweeping). The undercut with the shank is inserted into the square hole of the anvil, then the workpiece is placed on the undercut, and a forging chisel is installed on top, as shown in Fig. 8, d, and hit the chisel with a sledgehammer. In this way, the metal is simultaneously cut on both sides with a chisel and undercut.
More productive is mechanized felling metal using pneumatic hammer(Fig. 9), operating under the influence of compressed air at a pressure of 5-6 kgf/cm2.
Rice. 8. Tool for chopping thick steel in a cold state: o, b - blacksmith chisels, c - sharp-nosed sledgehammer, d - blunt-nosed sledgehammer, 3-" position of the chisel and cutting when chopping
Compressed air is supplied to the hammer through hoses from the compressor. A pneumatic hammer consists of a cylinder into the end of which a chisel is inserted, a piston moving in the cylinder, and an air distribution device. Thanks to the air distribution device, the piston receives forward and return motion and moves quickly, forward and backward along the cylinder. During forward movement, the piston hits the chisel, which cuts the metal.
Rice. 9. Pneumatic hammer: a - diagram, 6 - chisel for a pneumatic hammer; 1 - piston, 2 - spool, 3, 4, 5. 9, 10 - channels of the air distribution device, 6 - trigger, 7 - nipple, 8 - annular recess, 11 - cylinder
During the working stroke of the piston compressed air enters through the channel into the right side of the cylinder; at this time, air is displaced from the left side of the cylinder through the channel, annular groove and channel. At the end of the working stroke, compressed air, passing through the channel, moves the spool to the right and goes along the channel, moving the piston back. Air leaves the right side of the cylinder through the channel. Towards the end of the return stroke, the channel is blocked by the piston, the air in the right side of the cylinder begins to compress, moves the spool to the left and the working stroke begins again.
Rice. 10. Cutting a cast iron pipe a - position of the pipe and tool, b - perpendicular position of the chisel
The hammer is put into operation by pressing trigger 6. The worker holds the hammer with both hands and directs the chisel to the cutting site.
Cast iron pipes are cut with a chisel on wooden supports. First, a cutting line is marked along the circumference of the pipe with chalk, and then, placing linings under the pipe, in two or three passes they cut the pipe with a chisel along the marking line (Fig. 10, a), gradually turning it. After checking the depth of the cut groove, which should be at least 1/3 of the thickness of the pipe wall, a part of the pipe is separated with light blows of a hammer.
When working, the chisel must be held perpendicular to the axis of the pipe (Fig. 10, b). The end of the pipe at the cut point must be smooth, perpendicular to the axis of the pipe and coincide with the intended cut line. The correctness of the end is checked by eye, and for control - with a square. More productive cutting process cast iron pipes on manual screw press Khramkova.
A manual screw press (Fig. 11) consists of a welded frame, two side posts with threaded necks in the upper part, onto which a crossbar is attached, attached to the posts with nuts. A special nut with a worm thread is fastened to the traverse with a nut and screw, along which the lead screw moves.
A flywheel is mounted at the top of the lead screw. In the lower part of the racks there is a lower fixed holder with an insertable lower knife, and in the upper part of the racks there is an upper movable holder with an insertable upper knife. The upper movable cage is attached to the lead screw using a plate and bolts and rises and falls with it. The side posts are guides for the upper frame. A channel with posts at the ends is welded to the bottom of the frame plate. This channel is a guiding element when laying the pipe for cutting.
Rice. 11. Manual screw press for cutting cast-iron sewer pipes and the position of the knives when cutting pipes: 1 - lower fixed frame, 2 - frame, 3 - upper movable cage, 4 - bolt, 5 - stand, 6 - traverse, 7 - lead screw, 8 - flywheel, 9 - nut, 10 - screw, 11 - special nut, 12 - lining, 13 - upper knife, 14 - pipe, 15 - lower knife; position / - with the upper holder raised, position // - with the upper holder lowered, position /// - at the moment of cutting the pipes
The knives are attached to the clips with bolts. Inner diameters The blades of the knives should be 2 mm smaller than the outer diameters of the pipes being cut.
Cast iron sewer pipes with a diameter of 2 and 4" are cut using a manual screw press. For each pipe diameter there is a pair of knives and a pair of rollers installed on the channel to feed pipes to the knives.
Work on the press is performed as follows.
First, knives and rollers are installed in accordance with the diameter of the pipes being cut. Using a flywheel, lift the upper clip with the knife and place the pipe on the rollers so that the cutting line coincides with the tip of the lower knife. Then, with a sharp jerk, turn the flywheel in the opposite direction, while lowering the lead screw with the upper knife. From the sharp pressure of the lower and upper knives, a cut first appears on the sides of the pipe, the pipe wedges and then splits into two parts.
The press is serviced by one worker. It takes 1 minute to cut the pipe.
Mechanism VMS-36 (Fig. 12) for cutting cast iron sewer pipes with a diameter of 50 and 100 mm works on the principle of a drive press.
The mechanism has a welded frame on which a gearbox with two heads is mounted. Pipe cutting is done using four movable knives mounted in the chuck of each mechanism head. One head is designed for cutting pipes with a diameter of 50 mm, the second - for pipes with a diameter of 100 mm.
Rice. 12. Mechanism for cutting cast iron pipes VMS-36: 1 - frame, 2 - heads, 3 - knives
The mechanism is powered by an electric motor with a power of 1 kW and a speed of 930 per minute. The engine is started using push-button starters.
To cut pipes, first turn on the electric motor. Then they take a pre-marked pipe and lay it on supports so that the marking line on the pipe coincides with the knife blade. After this, press the pedal with your foot. The knives are lowered onto the pipe, which is cut along the marking line by the pressure of the knives. After. After completing the chopping cycle, the knives return to their original position and the operation of the head automatically stops. The pipe cutting time for one cycle is 3 seconds.
Each of the four knives covers the pipe being cut at a length equal to a quarter of its circumference.
In Fig. 13 planes are shown cutting knives, the geometry of which takes into account the characteristics of the material being cut, i.e., the fragility of cast iron.
To prevent destruction and ensure a smooth and smooth cutting surface of the pipe being cut, the cutting edges of the knives are made intermittent due to cut transverse grooves. The radius of the circle formed by the cutting edges of the knives must be less than the outer radius of the pipe being cut. The blade sharpening angle is 60°. The cutting process occurs as follows.
When approaching, the knives first touch the pipe at eight points. As they approach further, they crash into the pipe; holes are formed, located around the circumference. Microcracks appear near the holes, directed from hole to hole and deep into the metal. During the process, microcracks merge and running cracks are formed in the same direction, which advance the feed of the knives. This causes one end of the pipe to separate from the other.
Using knives of the described design, rings 20 mm long can be cut from cast iron sewer pipes.
Rice. 13. Planes of cutting knives: 1 - pipe, 3 - knives
When chopping, in order to avoid bruises and injuries, the following precautions must be observed: – firmly place the hammer or sledgehammer on the handle; – securely strengthen the metal in a vice and, when chopping on an anvil, support the part of the workpiece being chopped off; – use fencing nets when cutting hard or brittle metal so that flying fragments do not injure a person working or being nearby; – work with serviceable tools and on serviceable machines; – when cutting pipes on a press, wear gloves.
Before cutting pipes, it is necessary to check the serviceability of the mechanism, electrical equipment and protective fences.
Metal chopping is used to remove an excess layer of metal, cut out a hole, or cut a workpiece into pieces. The cutting is done on an anvil or a massive metal plate. Smaller parts for cutting are clamped in a vice.
It should be noted that when cutting, high precision processing is impossible; it is used either for rough processing of the workpiece or in cases where precision is not required.
Metal chopping tool
The following metalworking tools are used in the process of cutting metal: chisels, cross-cutters and groovers.
The cutting blade of a plumber's chisel is shaped like a wedge. The blade and head of the chisel must be hardened and tempered. The chisel head is a truncated cone with a semicircular base. This is done so that the hammer blow always falls in the center of the striker. The length of the chisel is usually 10-20 cm, the width of the blade is from 5 to 52 mm. The sharper the chisel is sharpened, the less impact force is required to cut metal. However, it must be borne in mind that hard and brittle metals require larger angle sharpening. In other words, hard metals cut with a blade with a more blunt sharpening angle. Thus, for cutting bronze, cast iron, hard steel and other hard materials, a chisel blade sharpening angle of 70° is required. Medium-hard steel should be cut with a chisel with a blade sharpening angle of 60°. Soft materials - copper, brass - can be chopped at a sharpening angle of 45°. Very soft materials, such as aluminum alloys and zinc, require a sharpening angle of 35°.
To cut out narrow grooves and grooves, a type of chisel with a narrower cutting edge is used. This instrument is called a crossmeissel. The working surface of the crossmeissel is sharpened in the same way as that of a chisel.
It is most convenient to cut out lubrication grooves in bearing shells and bushings using groovers. Their main difference from chisels and cross-cutters is the curved edge of the cutting part.
When working with a chisel, depending on the purpose of the work, three types of blows are used.
A brush blow is used to remove a thin layer of metal, minor irregularities, and also when it is necessary to cut a sheet of thin steel. Wrist strikes should be performed at a pace of 40-60 beats per minute, with only the hand moving. When swinging, it is recommended to unclench your fingers, holding the hammer handle only with your index and thumb, and when hitting, squeeze the hand.
An elbow strike has greater force compared to a wrist strike. The rate of blows is slow, about 40-50 per minute. When swinging your arm, it is recommended to bend your elbow to full, the ring and middle fingers Unclench slightly. Elbow strikes are used to cut grooves and grooves, as well as to remove a layer of medium-thick metal.
The shoulder strike is the most powerful. The force of the blow is achieved by a large swing, in which the arm moves in the shoulder joint. The fingers, hand and elbow work as with the wrist and elbow strike, but when swinging, the arm, bent as much as possible at the elbow joint, should be raised so that the hand is at ear level. The pace of the blows should be even slower - 30-40 per minute. Such blows are used for processing large surfaces, chopping thick metal, and also in cases where it is necessary to remove a large allowance in one chisel pass.
The quality of the cutting and the safety of the person doing it also depend on how he holds the tool. The fingers on the hammer handle are located at a distance of 15-30 mm from its end, and thumb placed on the index finger. The chisel should be held at a distance of 20-30 mm from its head; fingers should not be squeezed tightly. The likelihood of the hammer jumping off the chisel head is significantly reduced if top part chisels, put on a rubber washer with a diameter of 50 mm and a thickness of approximately 10 mm.
When performing this type of work with metal, it is important to ensure that the chisel is positioned correctly relative to the workpiece being processed. In the case of cutting along the plane of the jaws of the vice, the angle between the axis of the chisel and the plane of the jaws should be approximately 45°. When cutting is directed perpendicular to the plane of the jaws of the vice when removing a layer of metal, the angle between the plane of the workpiece and the axis of the chisel should be 30-35°. If the angle is too large, the chisel will go deep into the metal upon impact, creating a significant unevenness of the processed surface. If the angle of inclination is not large enough, the chisel will slide along the surface of the metal rather than cutting it.
An important note - when new to working with metal, when hitting a chisel with a hammer, they usually look at the head of the chisel, which the hammer hits. This is a serious mistake that leads to a decrease in the quality of work. You need to look at the cutting edge of the chisel to control the angle of inclination and see the result of each blow. In this case, it is possible to control the quality of work and adjust the chisel inclination and impact force without interrupting work.
When placing the workpiece in a vice, you need to ensure that the marking marks are located exactly at the level of the jaws and are not skewed. The part of the metal to be cut (chips) must be located above the level of the vise jaws.
- Metal cutting
Metal cutting in modern plumbing classified as auxiliary operations. It is carried out if necessary to remove from metal surface hardened crust, divide the workpiece into several parts, eliminate tides and various irregularities on castings and forgings.
1
Metal chopping is usually done using a sledgehammer, a cross-cutting hammer, a hammer, a forge and a chisel on a plate, in a regular vice or on an anvil. It is also possible to cut steel or non-ferrous metal sheets using a guillotine.
A chisel is a solid steel rod with a wedge-shaped cutting edge. If you are chopping and cutting metal that is classified as non-ferrous, the sharpening angle of the chisel is from 35 to 45 degrees. But when processing steel sheets, the specified angle is chosen to be 60 degrees.
A crosspiece is a narrow chisel that is used to produce narrow grooves and grooves. The working parts of a narrow and ordinary chisel must be hardened to a length of about 3 centimeters. It is also necessary to harden the metal on the head of the tool (by about 1.5–2.5 centimeters) so that it cracks and does not become discolored when the chisel is hit with a hammer.
Plumbing most often involves the use of chisels with blades of 2 and 2.5 centimeters (the width of the working tool) with a total length of 20 and 17.5 centimeters. Crosspieces have a smaller blade width (no more than 10 cm) and a length of up to 17.5 cm. Note that the heads of chisels (regular and narrow) are usually given a cone-shaped shape, which:
- reduces the risk of a mushroom-shaped cap forming on the head;
- facilitates the process correct application hitting the tool with a hammer.
It is very important to ensure that the chisels do not have any serious defects on their surface (for example, spots or deep cracks). Safety precautions strictly prohibit the use of such a tool to perform any type of metal processing (bending, chopping, cutting).
Chisels should be sharpened periodically to ensure they do not lose their cutting ability.
Sharpening is carried out using abrasive wheels on special sharpening machines. When performing this process, the chisel blade is cooled (ordinary water is used). If you do not cool the tool, there will be excessive heating of its working part, which in most cases leads to tempering, which will simply ruin the chisel. Safety precautions prohibit them from working after unsuccessful hardening.
Metal cutting (as well as its bending) is carried out using metalworker's hammers of standard weight (from 400 to 800 grams). Their oval-shaped handles are made of wood with high performance viscosity and hardness (rowan, maple, birch, oak). The length of the handles varies between 35–45 centimeters; they should not contain cracks or knots that could damage the hands of the person processing (bending, cutting, chopping) metal products.
Separately, let’s say that the ends of the handles of chopping hammers must be fixed with thin (1–3 millimeters) wedges made of steel or wood. Metal wedges are roughened after installation, and wood wedges are secured with special glue.
2
Depending on how the working tool is positioned in relation to the product during the operation, two cutting options are distinguished. She may be:
- vertical;
- horizontal.
The vertical process is performed on an anvil or on a slab. With this kind of cutting, products requiring processing are laid horizontally on work surface, and the chisel is placed vertically in relation to them. Horizontal cutting is carried out in a vice. In this case, the edge (back) of the working tool is mounted to the jaws of the vice (to their plane) at a very small angle (almost completely horizontal).
Sheet metal cutting is often done on a slab (on an anvil). In this case, the tool is placed on the mark (special markings applied to the workpiece), then one blow is carried out with a hammer. After this, the blade is mounted in such a way that half of it is placed in the hole that was made. Cutting the sheet according to this scheme, firstly, simplifies the process of installing the chisel in the desired position, and secondly, it guarantees a continuous cut.
In cases where sheet metal with a thickness of more than two millimeters is being cut, the product is marked on both sides. In this case, the workpiece is processed first on one side, then it is turned over to the other side and cut completely. If the sheet thickness is less than two millimeters, it is recommended to place a piece of soft grade steel on its reverse side. This will prevent the working tool from becoming dull when it hits the anvil.
Another point that should be taken into account when processing sheet products with complex configurations is that they require cutting a small groove of shallow depth. The indicated groove is made from the marking at a distance of about 1–2 millimeters. After this, you can cut the metal along the groove at full force until the cut contour shows itself on back side products. And then you will need to complete the operation by turning the workpiece over.
Bending and cutting of sheets can also be done in a vice. In this case, the product is fixed so that the markings are located several millimeters lower in relation to the marking jaws. Chopping metal in a vice under such conditions allows you to leave a small allowance on the product, which is used for finishing edges of the sheet (filing them). The cutting tool is tilted to the edges of the vice jaws at an angle of 45–60 degrees, and to the cutting plane – at an angle of no more than 40 degrees.
3
Many large enterprises use electric and pneumatic hammers, which greatly facilitate the metal processing process. Sheet blanks They are often cut out with a guillotine, using special stamps and presses. To process high-strength steels, plasma or technology can be used. In addition, a machine for cutting reinforcement is often used (in essence, we are talking about cutting metal with a guillotine).
Industrial cutting and bending metal sheets and products due to the mentioned units significantly simplifies the metalworking operation and also reduces the cost of work. It makes sense to use a guillotine or a press when products are produced from metals of any kind. non-standard forms. Chopping machines are indispensable in the production of embedded parts and steel strips.
Guillotine processing involves the use of knives and scissors to cut metal. These tools do not crumple the edges of the workpieces; their cuts are very precise and truly neat, which is rarely achieved when using a hammer and chisel. Also, cutting with a guillotine ensures the absence of:
- sickle-shaped deviations;
- hangnails;
- uneven bevels;
- small nicks.
Moreover, the mentioned flaws do not appear on the material even when workpieces with a small thickness are processed.
Industrial presses (equipped with an electric motor, screw for manual operation) are usually used for chopping made of cast iron. Such mechanisms function quite simply. The mechanic mounts the rollers and knives of the press to the cross-section of the pipes being processed, then places the tubular products on the rollers, ensuring that the blades of the lower part match cutting tool with the intended cutting line.
After this, the engine starts, if we are talking about an electrically driven machine, or manually lowers the upper knife onto the pipe. When the knives are compressed (from below and from above), a cut is formed on the workpiece (it is located on the sides of the pipe). Then the product wedging occurs and it splits. The design of the presses is such that one specialist can service such mechanisms.
