Chopping is a metalworking operation in which, with the help of a cutting tool (chisel, cross-cutter or groover) and a percussion tool (machinery hammer), workpieces or parts, excess layers of metal are removed or the workpiece is cut into pieces.

Felling is carried out in cases where it is not required high precision processing. The processing accuracy achieved when cutting is 0.4-0.7 mm.

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

In addition, cutting is used when it is necessary from rod, strip or sheet material cut off some part.

The cutting is done in a vice, on a plate or on an anvil. When cutting, small-sized blanks and castings are secured in a chair vice. Trimming of weld defects and bosses in large parts is carried out on site.

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

The means of mechanizing metal cutting are: replacing the cutting with an abrasive tool, as well as replacing the manual chisel with a pneumatic or electric chipper.

When starting chopping, the mechanic must prepare his workplace. Taking a chisel and a hammer out of the workbench box, he places the chisel on the workbench on the left side of the vice with the cutting edge facing him, and the hammer with right side vice with the striker pointing towards the vice.

The correct position of the mechanic's body is of great importance for cutting. When chopping, you need to stand steadily at the vice, half-turning towards it; The worker’s body should be to the left of the vice axis. Place your left leg half a step forward so that the axis of the foot is located at an angle of 70-75° relative to the vice. Move your right leg back a little, turning your foot at an angle of 40-45° relative to the axis of the vice.

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 grasped with four fingers and pressed against the palm; in this case, the thumb is placed on the index finger and all fingers are squeezed tightly. Hold the chisel with your left hand, without squeezing your fingers too tightly, at a distance of 20-30 mm from the head (Fig. 32, b).

During the cutting process, the chisel should be directed at an angle of 30-35° relative to the surface being processed (Fig. 33, a). At a smaller angle of inclination, it will slide rather than cut (Fig. 33, b), and at a larger angle, it will unnecessarily go deeper into the metal and produce large processing unevenness (Fig. 33, d).

Also essential for the process of manual cutting in a vice is correct installation chisels towards vertical plane fixed vise jaw. Normal installation cutting edge chisels should be considered an angle of 40-45° (Fig. 34, a). At a smaller angle, the cutting area increases, the cutting becomes heavier, and the process slows down (Fig. 34, b). At a larger angle, the chips, curling,

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

The quality of the cut depends on the type of swing and hammer blow. There are blows of the hand, elbow and shoulder. In a wrist swing, hammer blows are made with the force of the hand. This blow is used for light work to remove thin chips or when removing small irregularities. With an elbow strike, the arm bends at the elbow, resulting in a more powerful blow. The elbow strike is used in ordinary cutting, 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 greatest, and the blow is the strongest. The shoulder blow is used when chopping thick metal, when removing large layers in one pass, cutting metal and processing large planes.

When chopping using a wrist blow, the average is 40-50 blows per minute; with heavier work and shoulder impact, the cutting rate is reduced to 30-35 beats per minute.

The impact 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 that the hammer handle and chisel form a right angle. You can chop only with a sharply sharpened chisel; a blunt chisel slips from the surface, this quickly tires the hand and, as a result, the correctness of the blow is lost.

The size of the chips removed by a chisel depends on physical strength working, the size of the chisel, the weight of the hammer and the hardness of the metal being processed. The most productive is considered to be cutting, in which a layer of metal 1.5-2 mm thick is removed in one pass. When removing a layer of greater thickness, the mechanic quickly gets tired, and the cutting surface turns out to be unclean.

Chopping brittle metals (cast iron, bronze) should be done from the edge to the middle of the workpiece to avoid chipping off the edge of the part. When cutting tough metals ( mild steel, copper, brass) it is recommended to periodically wet the cutting edge of the chisel machine oil or soap emulsion.

Chopping in a vice can be done at the level of the jaws of the vice or above this level - at the marked marks. At the level of the vise jaws, thin metal is most often cut, and above the level - wide surfaces of the workpiece.

When chopping wide surfaces To reduce the time, you should use a cross-cutting tool and a chisel. First, grooves are cut with a cross-section, and then the resulting protrusions are cut off with a chisel.

To perform chopping correctly, you need to have good command of the chisel and hammer, that is, hold the chisel and hammer correctly, without slipping, and correctly swing and hit the head of the chisel with the hammer.

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Metal cutting

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

Cutting part chisels, like any other cutting tool, have the shape wedge .

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

A special chisel is used to cut grooves - kreutzmeisel(picture on the right).

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

Before chopping, the workpiece is secured in a vice slightly to the left of the right edge of the jaws so that there is room for installing the chisel (Fig. on the left). The hammer is placed with the striker to the left on the workbench to the right of the vice, and the chisel is placed on the left, with the cutting part towards itself. A protective mesh (or screen) must be installed at the cutting workplace to protect others from metal fragments.

When chopping, it is very important to adopt the correct working posture (picture on the right). You should stand straight, your body should be turned towards the vice, your right shoulder should be against the head of the chisel. For stability, the left leg should be pushed forward, the body rests on the right leg.

The chisel and hammer are held so that the striking part and the edge of the handle protrude 15...30 mm (Fig. on the left).

Chopping in a vice can be done according to the marking marks and according to the level of the vice jaws. In the first case, the workpiece is installed so that the marking mark is 1.5... 2 mm above the jaws of the vice. The chisel is placed at an angle of 30... 40° (fig. on the right) to the surface to be processed. After each blow, return the chisel to its original position.
In the second case, the marking marks 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 strengths.
Distinguish carpal , ulnar And shoulder blows( see fig. below).

Kistev (rice. A) remove small irregularities and thin chips with a blow, elbow (rice. b) - cut off excess metal and cut the workpiece into pieces without large thickness. At carpal When struck, the hammer moves due to the movement of the hand.
At elbow When hitting, the arm bends at the elbow and the blow becomes stronger (Fig. b). Elbow the excess metal is cut off with a blow and the workpieces are divided into parts.
Shoulder blow (Fig. V) - cut down thick shavings, cut rods, strips of large thickness.

In cases where the workpiece cannot be secured in a vice, it is processed on stove(picture on the left). The chisel is placed vertically on the marking line and blows are struck.
After each blow, the chisel is moved halfway along the cutting edge. This makes it easier to position the chisel in the correct position and create a continuous cut. In workpieces of large thickness, marking marks are applied on opposite sides. First, cut to about half the thickness of the sheet on one side, then on the other.

When cutting a workpiece complex shape The cutting edge is placed at a distance of 1 ... 1.5 mm from the marking line and the workpiece is cut with light blows along the entire contour. After this, they chop along the entire contour with stronger blows. Then the workpiece is turned over and cutting is completed along the designated contour.

You can only work proper tool. The impact part of the chisel and hammer must be free of cracks and burrs.
The hammer handle must be firmly seated and free of cracks.
Do not check the quality of the cut by touch.
At the end of the cut, ease the force of the blow.
To avoid injury, place a rubber washer on the top end of the chisel.
Felling can only be done if there is protective screen and safety glasses.
You cannot stand behind someone working.

Manual cutting is a labor-intensive operation. IN 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, blanks from sheet metal are cut out on presses using special dies. Among the high-performance methods that are used in Lately, it should be noted oxygen, laser, etc. These installations serve metal cutters.

The variety of chisels and crosscuts is shown in the figure below.

Training Guide for Preparation
workers in production

Workshop on plumbing work

Sharpening chisels and crosspieces

The quality of metal cutting depends on the serviceability and correct sharpening cutting tool. The sharpening angle is chosen depending on the type of metal being processed: 70° - for cast iron and bronze; 60° - for steel; 45° - for copper and brass.

The chisel or kreidmeisel is sharpened to sharpening machine in the following sequence.

1. First, they study the labor safety requirements when working on sharpening machines, then inspect the sharpening machine and prepare it for start-up.

2. Put on safety glasses and turn on the sharpening machine motor.

Rice. 50. Sharpening the chisel and cross-section on a sharpening machine

3. Take a chisel or cross-section in your hands (Fig. 50), smoothly bring the cutting edge to cylindrical surface grinding wheel (towards the movement).

4. With light pressure, the chisel or crosspiece is slowly moved left and right across the entire width of the circle, alternately sharpening one or the other surface. When sharpening, it is necessary to ensure that the cutting edge is straight, and the bevels of the cutting surfaces are symmetrically located relative to the axis of the chisel or cross-section. To reduce heat during sharpening, the end of the chisel or crosspiece is periodically cooled in water.

Rice. 51. Checking the sharpening angle of the chisel using a template

The quality of sharpening is checked: a) the value of the sharpening angle is controlled using a flat template with angular cutouts of 70, 60, 45° - in the light (Fig. 51); b) the straightness of the cutting edge is checked with a ruler; c) the correct sharpening of the sharpening angle in relation to the axis of the chisel is established by eye.

Control questions

1. List the basic techniques for chopping metal and when they are called hand, elbow and shoulder strikes?
2. In what cases are chisels and crosspieces used in work?
3. What are the sharpening angles of the chisel and cross-section for cutting cast iron and aluminum?
4. How to cut a workpiece from sheet steel and why is the cutting edge of the chisel rounded?
5. What are the requirements safe work at manual chopping and sharpening the chisel and crosspiece?

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 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.

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.

Percussion instruments

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 heavy work, hammers weighing 4-16 kg - sledgehammers - are used. In addition to hammers with steel strikers, when assembling and repairing mechanisms and machines, hammers with inserts made of soft metals (copper, aluminum, lead) are used, as well as wooden hammers with round and rectangular strikers.

Sharpening of cutting tools is done manually on 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. For precise hammer blows cutting tool The worker’s body should be turned half a turn towards 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 2mm thick is cut through with one blow, more than 2mm is 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 and strip metal in a vice, the workpiece is clamped so that the marking line coincides with the level of the jaws.

The chisel (cleaver with a handle) is one of the oldest tools for processing cold or hot metal. Scientific and technological progress has contributed greatly minor improvements into this tool, offering high-strength materials for use and formalizing the sharpening angles of the blade. However appearance and the methods of working with a chisel have not changed for many centuries. This article presents full information about blacksmith tools for cutting metal, types, the possibility of making it yourself or purchasing a factory-made cleaver.

Blade and head of a chisel are subjected to hardening and tempering. The length is usually 10-20 cm., and the blade width is 5-5.2 mm. Blade sharpening angle depends on the metal for which this chisel will be used - the harder or more brittle the metal is, the more obtuse the sharpening angle should be. Standard sharpening angles for cutting various metals the following:

• hard steel, bronze, cast iron - 70 degrees;
• medium hard steel – 60 degrees;
• copper, brass – 45 degrees;
• zinc, aluminum alloys– 35 degrees.

It is also a widely used tool for more special tasks, such as cutting out grooves and narrow grooves. This tool is called crossmeisel.

The main design difference blacksmith's chisel from a metalworker's is a hole in its middle part for mounting on 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 cutting forge chisel

What types are there: intrinsically safe with a wooden handle and others, photo

There are several types of blacksmith chisels:

• Non-sparking tools are designed for use in potentially explosive areas. The striker of such chisels is made of bronze alloys, which ensures antimagnetic properties and high level corrosion resistance, handle made of wood.

Blacksmith chisel. Photo ForgingPRO

• Chisels with thin blade are designed for cutting hot metal, with thicker ones for separating cold workpieces.
• The shape of the working part can be straight or round.

Sweeps

The undercut is a tool that acts like an upside-down chisel. Undercuts 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 a hook mounted on an anvil and a chisel - these tools are produced in pairs.

Materials for making chisels and hooks

Standards require the following materials to be used in the manufacture of chisels:

• carbon tool steels (U7, U8, U9, U7A, U8A, 6ХС, 9ХС), intended for cutting metals;
• structural steels (45, 50, 40Х, 60С2), equipped carbide inserts(VK15, VK20, VK25, VK30, VK8V), designed for cutting stone.

Sharpening chisels, angle

Sharpening is performed on a special sharpening machine. The chisel is placed on the tool rest and, pressing slightly, slowly moved along the entire width of the rotating abrasive wheel, alternately sharpening one or the other edge. In this case, the blade should be lowered frequently cold water to prevent overheating of the metal, during which it loses the necessary hardness.

After sharpening is completed on the grinding wheel, the burrs are removed from the chisel, and then the cutting edge is threaded on the abrasive wheel.

Hot forging chisel with a sharpening angle of 70-80 degrees

Knife sharpening angle chisels for hot cutting is no more than 50, and cold - not less than 60 degrees.

Important! The wooden handle on which the forging chisels are mounted is not wedged (to avoid kickback and breakage).

In conclusion The correct sharpening angles of the blade are checked with a special template. As such a template, a metal block 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 correct sharpening.

Requirements

The main requirement for a blacksmith chisel is its serviceability. Safety of using the tool includes several characteristics that the chisel and its individual parts must have:

• The strikers 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 towards the free end and a smooth surface, without cracks. Metal handles are also used, which also do not fit tightly, and rope handles.
• Chisel length should not be less than 150 mm.
• When working with a chisel, individual parts of the metal may fly off to the sides, so it is necessary to wear safety glasses.

Malfunctions

Among the most common breakdowns of a forging chisel are:

• break;
• dullness;
• the appearance of notches;
• deformation, curvature of the striker;
• cold hardening on the striker, which is fraught with chips and flying fragments.

Chisel striker broken

Malfunctions arise in the event of incorrect felling, when long-term operation tool, if there is a manufacturing defect. Periodically (at least once a quarter) it is necessary to inspect the chisel for any damage to the striker or handle. Faulty tools that have defects must be removed from service.

With your own hands, the manufacturing process (forging) in a forge, how to harden

Forge chisel possible make it yourself, in industrial and home conditions. How production is carried out, how to properly attach the firing pin to a metal handle, and how to harden it is clearly demonstrated in the video.