Metal cutting
FELLING - this is a locksmith operation in which a metal layer is removed from the surface of the workpiece using cutting and impact tools or the workpiece is divided into parts.
Chopping is a rough, preliminary operation. It is designed to prepare the workpiece for further processing.
Cutting is used to remove large irregularities, burrs, sharp edges from blanks, cutting grooves and grooves, cutting holes in sheet material.
In one pass, a metal layer of up to 2 mm can be removed. The processing accuracy leaves 0.5-1 mm.
When cutting, a chisel and crosshead are a cutting tool; a hammer is a percussion tool.
The shape of the cutting part of any cutting tool is a wedge. The force that needs to be applied, the strength of the tool, and the size of the metal layer to be removed depends on how the wedge is pointed and how it is installed with respect to the workpiece being machined.
Chiselconsists of a working, middle and shock parts. The working part is sharpened, forming a cutting part with a 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.
Crossheadhas 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. The width of the cutting edge 2; 5; 8; 10; 12 mm.
Groove- A type of crosshead with a rounded cutting edge for cutting complex profile grooves. Make a length of 80; one hundred; 120; 150; 200; 300; 350 mm with a radius of curvature of the cutting edge 1; 1.5; 2.0; 2.5: 3.0 mm.
Percussion instruments
Two types of hand hammers are made: square hammer and round hammer
The hammer consists of a hammer and a crank. The main characteristic of a hammer is its mass. Hammer handles are made of hardwood (birch, oak)
For heavy work use hammers weighing 4-16 kg-sledgehammers. In addition to hammers with steel hammers, when assembling and repairing mechanisms and machines, hammers with soft metal inserts (copper, aluminum, lead), as well as wooden hammers with round and rectangular hammers, are used.
Sharpening of cutting tools is done manually on grinding machines. The following sharpening angles are recommended:
Hard materials (cast iron) 70 degrees
Medium Hardness (Steel) 60 degrees
Soft (brass, copper) 45 degrees
35 degree aluminum alloys
Point angles are controlled by a pattern.
Cutting is carried out in a vice, on stoves, and on anvils.
When cutting in a parallel vise, strike in the direction of the fixed sponge. For accurate striking with a hammer on a cutting tool, the worker’s body should be turned half a turn to the axis of the vice. The mass of the hammer is selected depending on the width of the cutting part of the chisel and the thickness of the metal layer to be removed, 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 crosshead of the chisel.
The metal is cut on the plate with a vertical position of the chisel and a shoulder blow with a hammer. Strip and sheet metal with a thickness of up to 2 mm are cut from one blow, more than 2 mm are cut through about half the thickness on both sides, and then broken, bent to one and the other side.
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 in a vice of sheet and strip metal, the workpiece is clamped so that the marking line coincides with the level of the jaws.
Perhaps the most common operations in plumbing are metal modeling: filing, cutting, chopping, threading, drilling holes.
For metal cutting, the following bench tools are used: a chisel, crosshead and grooves (Fig. 4).
Fig. 4. Chopping tool: a - chisel; b - crosshead.
Fig. 4 (continued). Chopping tool: in - grooves; g - template for sharpening control.
Cutter Blade chisels(Fig. 4, a) has the shape of a wedge. The blade and hammer must be tempered and tempered. The chisel head is a truncated cone with a semicircular base. This is done so that the blow of the hammer always falls in the center of the striker. The length of the chisel is usually 100-200 mm, the width of the blade is from 5 to 52 mm. The sharper it is sharpened, the less impact force is required for cutting metal. However, it must be borne in mind that hard and brittle metals require a larger sharpening angle, and not a smaller one. In other words, hard metals are cut with a blade with a blunter sharpening angle. So, for chopping bronze, cast iron, solid steel and other solid materials, a blade sharpening angle of 70 ° is required. Steel of medium hardness needs to be cut with a chisel with a sharpening angle of 60 °. Soft materials - copper, brass - can be chopped at a grinding angle of 45 °. Very soft materials, such as aluminum alloys and zinc, require a sharpening angle of 35 °.
To cut narrow grooves and grooves, a variety of chisels with a narrower cutting edge are used. This tool is called crosshead(Fig. 4, b). The technique and the angle of sharpening the working surface of the crosshead for chopping materials of different hardness are similar to sharpening a chisel.
It is most convenient to cut lubrication grooves in bearing shells and bearings grooves (Fig. 4, c). Their main difference from the chisel and crosshead is the curved edge of the cutting part.
The quality and speed of metal cutting depends on the sharpening of the cutting tool.
In order to perform the operation of sharpening a chisel or crosshead, a locksmith will need a grinder and a simple template. To do this, you can use any sufficiently powerful electric motor, on the axis of which it is possible to fix removable grinding wheels (since the cutting tools are made of tool steel - carbon, alloy and high-speed, it is advisable to use electrocorundum wheels with a grain size of 40, 50 or 63 on a ceramic bond) . The template is a bar of metal of small thickness, with grooves cut out in it, making angles of 35, 45, 60 and 70 ° (Fig. 4, d).
During sharpening, the chisel should be located at an angle of 30–40 ° to the periphery of the circle. It should be moved along the entire width of the circle with a slight pressure, periodically turning over with one or the other side - this ensures the symmetry of the cutting edges and the uniformity of sharpening. The side faces are sharpened so that after sharpening the edges they remain flat, the same in width and have one angle of inclination.
After each contact of the chisel blade with the grinding wheel, it should be immersed in water for rapid cooling (otherwise, with gradual cooling, the blade may lose its chopping properties).
The burrs remaining on the blade after sharpening must be removed with a fine-grained abrasive block.
From the book: Korshever N.G. Metal Works
Chisel (billhook with cuttings) is one of the oldest tools for processing cold or hot metal. Scientific and technological progress has made a very minor improvements into this tool, proposing to use high-strength materials and formalizing the blade sharpening angles. However, the appearance and methods of working with a chisel have not changed for many centuries. This article provides complete information about the forging tool for cutting metal, types, the ability to do it yourself or purchase a factory-made billhook.
Chisel blade and hammer subjected to hardening and tempering. The length is usually 10-20 cm., and the width of the blade is 5-5.2 mm. Blade sharpening angle depends on the metal for which the chisel will be used for cutting - the harder or more brittle the metal is, the more blunt the grinding angle should be. Standard sharpening angles for cutting various metals the following:
- solid steel, bronze, cast iron - 70 degrees;
- steel of medium hardness - 60 degrees;
- copper, brass - 45 degrees;
- zinc, aluminum alloys - 35 degrees.
The tool is also widely used for more specialized tasks, such as punching grooves and narrow grooves. This tool is called crosshead.
The main design difference a blacksmith's chisel from a bench is a hole in its middle part for mounting on a wooden handle. Cutting part a blacksmith's chisel is called a knife, its length is from 30 to 50 mm. The length of the entire tool for cutting cold metal is 16-19 cm., For cutting hot metal - 18-24 cm.
Cold chisel forging
What are the types: intrinsically safe with a wooden handle and others, photo
There are several types of blacksmith chisels:
- The intrinsically safe tool is intended for work in potentially explosive zones. The hammer of such chisels is made of bronze alloys, which ensures the presence of antimagnetic properties and a high level of corrosion resistance, the handle is made of wood.
Blacksmith's chisel. Photo KovkaPro
- Chisels thin blade designed for cutting hot metal, with thicker - for the separation of cold billets.
- The shape of the working part is straight and round.
Hooks
Sweeping is a tool that acts like an inverted chisel. Sweeps are used to speed up the cutting of metal or to interrupt strip material.
The hooks have a tetrahedral tail, which is inserted into the corresponding groove on the anvil. Metal cutting is carried out between the hook mounted on the anvil and the chisel - these tools are produced in pairs.
Materials for the manufacture of chisels and hooks
Standards require the use of the following materials in the manufacture of chisels:
- tool carbon steel (U7, U8, U9, U7A, U8A, 6XC, 9XC) intended for metal cutting;
- structural steel (45, 50, 40X, 60C2), equipped with carbide inserts (VK15, VK20, VK25, VK30, VK8V), designed for stone cutting.
Chisel sharpening, angle
Sharpening is performed on a special grinding machine. The chisel is imposed on the handle and, slightly pressing, slowly move along the entire width of the rotating abrasive wheel, alternately sharpening one or the other face. In this case, the blade should often be lowered into cold water to prevent overheating of the metal, in which it loses the necessary hardness.
After sharpening on the grinding wheel, the burrs are removed from the chisel, and then the cutting edge is tucked on the abrasive wheel.
Hot chisel forging with a sharpening angle of 70-80 degrees
Knife sharpening angle the chisels for hot cutting is not more than 50, and cold - not less than 60 degrees.
Important! The wooden handle on which the blacksmith chisels are mounted does not wedge (in order to avoid kickback and breakage).
In conclusion the correct sharpening angles of the blade is checked with a special template. As such a template, a bar of metal is used in which grooves are cut. The angles in these grooves have the required values, therefore, by inserting a sharpened chisel blade into this groove, you can visually determine the correctness of sharpening.
Requirements
The main requirement for a blacksmith's chisel is its serviceability. The safety of using the tool includes several characteristics that a chisel and its individual parts should have:
- Fighters must have smooth surface, without chips, cracks, burrs, deformation.
- The handle must be made of hardwood or synthetic materials, should have an oval shape with a thickening to the free end and a smooth surface, without cracks. Metal handles are also used, also not tightly seated and cable handles.
- Chisel length should not be less than 150 mm.
- When working with a chisel, individual parts of the metal can fly to the sides, therefore it is necessary to use safety glasses.
Malfunctions
Among the most common damage to a blacksmith's chisel are:
- kink;
- dullness;
- the appearance of chipping;
- deformation, curvature of the striker;
- cold hardening on a striker, which is fraught with chips and flying fragments.
Kink chisel
Malfunctions arise in case of incorrect cutting, during prolonged use of the tool, in the presence of factory defects. Periodically (at least once a quarter), it is necessary to inspect the chisel for any damage to the hammer or handle. Defective tools that have defects must be removed from service.
Do it yourself, the manufacturing process (forging) in the forge, how to harden
Blacksmith chisel possible make yourself, in industrial and domestic conditions. How the production is carried out, how to properly insert the firing pin on the metal handle, as well as hardening is clearly demonstrated in the video.
Cutting an operation is called in which, with the help of a chisel and a bench hammer, layers of metal are removed from the workpiece or the workpiece is cut.
The physical basis of the cutting is the action of the wedge, the shape of which is the working (cutting) part of the chisel. Cutting is used in cases where machining of workpieces is difficult or irrational.
With the help of cutting, metal roughness is removed (chopped) from the workpiece, hard peel, scale, sharp edges of the part are removed, grooves and grooves are cut out, sheet metal is cut into pieces.
Felling is usually carried out in a vice. Cutting the sheet material into pieces can be performed 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 tool carbon steel U7A or U8A. It consists of three parts: shock, medium and working. Shock part 1 is tapering upward, and its apex (striker) is rounded; for the middle part 2 the chisel is kept during cutting; working (cutting) part 3 has a wedge-shaped shape.
Figure 8 Bench Chisel
The angle of sharpening is selected depending on the hardness of the material being processed. The following sharpening angles are recommended for the most common materials:
For solid materials (solid steel, cast iron) - 70 °;
For materials of medium hardness (steel) - 60 °;
For soft materials (copper, brass) - 45 °;
For aluminum alloys - 35 °.
Crosshead - a chisel with a narrow cutting edge (Figure 10), designed for cutting narrow grooves, keyways of low accuracy and cutting heads of rivets. 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 with a wide chisel.
Hand hammers , used in the cutting of metals, there are two types: round and with square briskly. The main characteristic of a hammer is its mass.
Round hammer hammers have a number : 1st to 6th . The nominal weight of the hammer No. 1 is 200 g; No. 2 - 400 g; No. 3 - 500 g; No. 4 - 600 g; No. 5 - 800 g; No. 6 - 1000 g. Hammers with a square hammer are numbered from 1st to 8th and weigh from 50 to 1000 g.
Material of hammers - steel 50 (not lower) or steel U7.
The working ends of the hammers are heat-treated to a hardness of HRC 49-56 at a length equal to 1/5 of the total length of the hammer at 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 - locksmith operation to split the whole a piece(blanks, parts) into parts. It is carried out without chip removal: with nippers, scissors and pipe cutters and with chip removal: with hacksaws, saws, milling cutters and special methods (gas cutting, anode-mechanical and electric spark cutting, plasma cutting).
The wire is cut with nippers (nippers), the 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 circular saws, in special ways.
The essence of the operation of cutting metal with pliers (nippers) and scissors is to separate the wire, sheet or strip metal into parts under pressure from two wedges moving towards each other (cutting knives).
Nippers cut (bite off) steel parts of circular cross section and wire. They are made with a length of 125 and 150 mm (for biting 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 sharply at an angle of 55-60 °. Nippers are made of tool carbon steel U7, U8 or steel 60-70. The sponges are heat treated to a hardness of HRC 52-60.
Manual scissors designed for cutting sheet mild 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 thermally machined to a hardness of HRC 52-58. The cutting edges of the blades are sharpened sharply at an angle of 70 °. When closed, the scissor blades 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 scissor handles 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. Scissors are made of U8A tool steel and heat treated to a hardness of HRC 52-58. The angle of sharpening of the cutting edges of the knives 75-85 °.
Pipe cutters designed for manual cutting of thin-walled (gas) pipes made of mild steel, cutting is performed without removing chips. 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 with a working roller; at the same time it is fixed on the guide rollers and tightened by a screw.
Hacksaw (Figure 9, a) is used to cut relatively thick sheets of metal and round or profile rolled products. Hacksaw can also cut slots, grooves, trimming and cutting blanks along the contour and other work. They are made of steel U8-U12 or 9XC with a hardness of the cutting part HRC 58-61, and the core - HRC 40-45. It consists of a frame. 1 tensioning 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 Manual hacksaw a - device, b - sharpening angles, c - tooth set-up “by tooth”, d - tooth set-up “by blade”. |
Each tooth of the blade has the shape of a wedge (incisor). On it, as on the cutter, distinguish the rear angle α, point angle β , the rake angle γ and the cutting angle δ \u003d α + β (Figure 9, b). When cutting teeth, take into account the fact that the resulting chips should be placed between the teeth before they exit the cut. Depending on the hardness of the materials being cut, the tooth tooth corners can be: γ \u003d 0-12 °, β \u003d 43-60 ° and α \u003d 35-40 °. In order for the width of the cut made by a hacksaw to be slightly larger than the thickness of the blade, the tooth alignment is performed “by tooth” (Figure 9, at)or “on the canvas” (Figure 9, g) This prevents the web from jamming and makes work easier. |
§ 3. Tools and devices for metal cutting
Cutting is a locksmith operation in which, using a cutting tool (chisel), excess metal layers are removed from the workpiece or part or the workpiece is cut into pieces.
With modern methods of processing material or workpieces, chopping metal is an auxiliary operation.
Metal felling is carried out in a vice, on a stove and on an anvil using a bench hammer, a chisel, a crosshead, a blacksmith's chisel and a sledgehammer.
Metal felling is horizontal and vertical, depending on the location of the chisel during the operation. Horizontal cutting is carried out in a vice. In this case, the rear face of the chisel is set to the plane of the jaw lips almost horizontally, at an angle of no more than 5 °. Vertical cutting is performed on a stove or anvil. The chisel is installed vertically, and the chopped material is laid horizontally on the plate.
Hammers weighing 400, 500, 600 and 800 are used for lockmaking. Hammers are mounted on handles made of hard and viscous wood (birch, maple, oak, mountain ash). Handles should be oval, with a smooth and clean surface, without knots and cracks. The length of the handle of a hammer weighing 400-600 g is 350 mm, the weight of 800 g is 380-450 mm. To prevent the hammer from slipping during operation, the end of the handle on which the hammer is mounted is wedged with 1-3 mm thick wooden or metal wedges. Wedges are placed along the major axis of the handle section. Wooden wedges are placed on the glue, and metal wedges are sealed so that they do not fall out.
The working part of the chisel and crosshead- (5, c, d) is hardened to a length of at least 30 mm, and the head is hardened weaker than the blade (to a length of about 15-25 mm) so that it does not crumble or crack when hit with a hammer.
The rest of the chisel and crosshead must remain soft. Chisels and crossheads should not have cracks, captivity and other defects.
The most commonly used chisels are 175 and 200 mm long with blades 20 and 25 mm wide. For cutting grooves in steel and cast iron, crossheads 150-175 mm long with a blade 5-10 mm wide are used. The chisel and crosshead heads are forged onto a cone, which ensures the correct direction of impact with a hammer and reduces the possibility of the formation of a mushroom cap on the head.
The angle of sharpening of chisels and crossheads depends on the hardness of the metal being processed. For chopping cast iron, hard steel and solid bronze, the tool sharpening angle is 70 °, for chopping medium and mild steel - 60 °, for chopping brass, copper and zinc -45 °, for chopping very soft metals (aluminum, lead) - 35- 45 °.
Grinding tools are sharpened on grinding machines with abrasive wheels. During sharpening, the working part of the tool (blade) is very hot and may release. When tempering, the hardness of 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. Figure 6 shows how to hold the chisel when sharpening and how to check the correct sharpening of the angle.
§ 4. Rules and techniques for cutting metal
Productivity and cleanliness of metal cutting depend on the correct working methods. When cutting, stand steadily and straight, half-turn to the vise. The hammer is supposed to be held by the handle at a distance of 15-20 mm from the end and inflict strong blows in the center of the chisel head. You should look at the chisel blade and not at its head, otherwise the chisel blade will go wrong. The chisel is supposed to be kept at a distance of 20-25 mm from the head.
Billets made of sheet steel or steel can be cut in a vise by the level of the sponges or by risks above the level of the jaws of the vise.
When cutting according to the level of the vice jaws (8, a, b), the workpiece is clamped firmly into the vice so that the upper edge protrudes 3-4 mm above the jaws and cut the first chip for the entire length of the workpiece. Then the workpiece is rearranged in a vice so that the upper rib protrudes 3-4 mm above the level of the jaws of the vice, and cut the second chip. So sequentially chop off the product to the desired size.
When cutting above the level of the vise jaws (8, c), the workpiece is clamped in risks in a vice so that the marked risk is above and parallel to the level of the vise jaws. Cutting is carried out according to marked risks sequentially, as in the case of cutting according to the level of vice jaws. When cutting the chisel should be located at an angle of 45 ° to the metal being cut off, and the head is raised upward at an angle of 25-40 °. With this arrangement of the chisel, the cutting line will be rooted and cutting will be faster.
A large layer of metal on a wide plane of the workpiece is cut as follows: the workpiece is clamped in a vice, a chamfer is cut off with a chisel, transverse grooves are cut with a cross-cutel, and then the protruding faces are cut with a chisel. When cutting through the grooves with the crosshead, the chip thickness should be no more than 1 mm, and when cutting the protruding faces with a chisel, from 1 to 2 mm.
Strip steel is cut on a stove or anvil (9). Pre-cut lines on both sides of the strip with chalk. Then, laying the strip on the anvil, set a bench chisel vertically on the marked risk and, with strong blows of a bench hammer, cut the strip into half its thickness. Then they turn the strip over, cut it on the other side and break off the chopped part.
Round metal is cut in the same way, with the rotation of the bar after each stroke. Chopping the bar around the entire circumference to a sufficient depth, break off the chopped part.
Carbon and alloyed structural steel with a thickness of up to 20-25 mm can be cut in the cold state on a stove or anvil using forging chisels (10, a, b) and a sledge hammer (10, c, d). To do this, on-t * “ip, Four sides of the workpiece are applied with chalk lines of the cut. Then the metal is laid on the anvil, the forging chisel is mounted vertically on the marking line and, with strong blows, the sledgehammers cut the metal along this entire line to the required depth, gradually rearranging the chisel. Metal is also cut from the other side or from all four sides, after which the chopped part is broken off. To speed up and simplify the felling, an auxiliary tool is used - nizhik (hooking). Cutting with a shank is inserted into the square hole of the anvil, then the workpiece is placed for cutting, and a blacksmith chisel is installed on top, as shown in 10, D and a hammer hit the chisel. Thus, simultaneous cutting of metal occurs on both sides with a chisel and a hook.
Cast-iron pipes are cut with a chisel on wooden lining. First, along the circumference of the pipe, the line of the cut is marked with chalk, and then, laying linings under the pipe, for two or three passes cut the pipe with a chisel along the marking line (I, a), gradually turning it. After checking the depth of the cut groove, which should be at least 7z of the pipe wall thickness, part of the pipe is separated with light hammer blows. During operation, the chisel must be held perpendicular to the axis of the pipe (11, b). The end of the pipe in the place of the cut should be flat, perpendicular to the axis of the pipe and coincide with the intended line of the cut. The correctness of the Butt is checked by eye, and controlled by a square.
§ 3. Mechanisms and devices for metal cutting
More productive is the mechanized cutting of metal with a pneumatic hammer (12), working under the action of compressed air with a pressure of 5-6 kgf / cm2. Compressed air is supplied to the hammer through hoses from the compressor. The pneumatic hammer consists of a cylinder /), into which a chisel, a piston / moving in the cylinder, and an air distribution device are inserted. Thanks to the air distribution device, the piston receives translational and reverse motion and quickly moves back and forth along the cylinder. With translational motion, the piston hits the chisel, which cuts the metal. The hammer is turned on by pressing the trigger 6. The worker holds the hammer with both hands and guides the chisel to the place of cutting.
A manual screw press (13) is used for cutting pig-iron sewer pipes with a diameter of 50 and 100 mm. It consists of a welded bed 2, two lateral struts 5, having a threaded neck in the upper part of the beam, on which the beam 6 is mounted. The beam is attached to the columns with nuts. On the traverse, with a nut and screw, the lower fixed holder with an inserted lower knife is placed in the lower part of the racks, and the upper movable holder 3 with an inserted upper knife in the upper part of the racks. The upper movable cage is fastened with a lead screw by a cover plate 12 and bolts 4 and with them rises and falls. Side racks 5 are guides for the upper clip. A channel with welded ends is welded to the bottom of the bed plate. This channel is a guiding element when laying a pipe for cutting.
Knives are bolted to the clips. The inner diameters of the blades of the knives should be 2 mm less than the outer diameters of the cut pipes. For each pipe diameter there is a pair of knives and a pair of rollers mounted on the channel for supplying pipes to the knives.
The press works as follows. First, knives and rollers are installed in accordance with the diameter of the pipes being cut. Having lifted the upper holder with the flywheel with the knife, lay the pipe on the rollers so that the cut line coincides with the tip of the lower knife. Then, with a sharp jerk, turn the flywheel in the opposite direction, while lowering the spindle with the upper knife. From the sharp pressure of the lower and upper knives, an incision appears on the sides of the pipe, the pipe wedges and then splits into two parts. The press is served by one worker.
The VMS-36A mechanism (14) for cutting cast iron sewer pipes with a diameter of 50 and 100 mm works on the principle of a drive press. A gearbox with two heads 2 is mounted on the welded bed / mechanism. One head is designed for cutting pipes with a diameter of 50 mm, the second for pipes with a diameter of 100 mm. The pipes are cut with four movable knives mounted in the cartridges of the heads of the mechanism. The mechanism is included in the operation from an electric motor with a power of 1.5 kW, with a rotation speed of 1420 rpm. The engine is started by foot pedal.
To chop the pipes, first turn on the electric motor. Then
take a pre-marked pipe and lay it on the supports so that the marking line on the pipe coincides with the knife blade. After that, they press the pedal with the foot. The knives are lowered onto the pipe, which is cut off along the marking line from the pressure of the knives. After chopping, the knives return to their original position and the operation of the head automatically stops. The cutting time of pipes of one cycle is 3 s. Each of the four knives covers the chopped pipe at a length equal to a quarter of its circumference. 15 shows the planes of cutting knives, the geometry of which takes into account the features of the material being cut, i.e., the fragility of cast iron. To prevent destruction and ensure a smooth and even cut surface of the pipe being cut, the cutting edges of the knives are made intermittent due to the cut transverse grooves. The radius of the circle formed by the cutting edges of the knives should be less than the outer radius of the chopped pipe. Knife sharpening angle 60 °. The cutting process is as follows.
When rapprochement knives at the first moment touch the pipe at eight points. With further approach, they crash into the pipe; holes formed around the circumference are formed. Microcracks occur near the holes, directed from hole to hole and deep into the metal. During the process, microcracks merge and running cracks of the same direction form, which are ahead of the blade feed. This leads to the fact that one end of the pipe is separated from the other.
Knives of the described design can be cut from cast-iron sewer pipes of a ring 20 mm long.
When cutting, the following precautions must be observed to avoid bruises and injuries:
firmly stick a hammer or sledgehammer on the handle;
reliably strengthen the metal in a vice and, when cutting on the anvil, support the cut-off part of the workpiece
use enclosing nets when cutting hard or brittle metal so that flying fragments do not damage a person who is working or who is near;
work with a working tool and working machines;
when cutting pipes on the press, work in gauntlets.
Before cutting pipes, it is necessary to check the serviceability of the mechanism, electrical equipment and protective fences.