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Metal bending and straightening

Techniques for manual and machine straightening of strip, sheet, round material and hardened products

In the process of editing by hand, the hammer must be held by the end of the handle, as well as when cutting metal. Blows should be applied only with the convex part of the striker; from strikes with the edge of the striker, nicks remain on the surface of the straightened part.

When editing, you need to choose the right places to hit. The blows should be well-aimed, commensurate with the magnitude of the curvature, and their number should gradually decrease as you move from the largest bend to the smallest. Editing is considered complete when all irregularities disappear and the workpiece is straight, which can be checked by applying a ruler. Hand and machine editing of metals should be done in gloves.

Manual dressing of strip metal is carried out on a straightening plate or anvil with a metalworker's hammer.

The simplest is the straightening of metal bent along a plane. This type of editing is the most common; it is usually performed without much difficulty. It is more difficult to straighten metal curved along the edge. If in the first case the task is to simply level the plane, then here one has to resort to tensile deformation of a part of the metal. Even more difficult is the straightening of twisted strips.

Sometimes all of these types of bends are found in one workpiece. To completely straighten such a metal, you need to implement a whole range of techniques.

Rice. 1. Billets from strip steel to be straightened (a, b, c); strip steel dressing techniques (d, e, f)

The curved strip is placed on the slab with the curved part upwards and, holding it with the left hand, with the right hand, strong blows are applied with a hammer to the convex places (Fig. 1, d), hitting first at the edges of the convexity and gradually, as the strip is straightened, bringing the blows closer to the middle of the convexity. The greater the curvature and the thicker the strip, the stronger the blows should be and, conversely, as the strips straighten, they weaken them, finishing with light blows. In the process of straightening, the strip must, as necessary, be periodically rotated from one side to the other. Having straightened the wide side, they begin to edit the ribs by turning the workpiece on the edge. After one or two blows, the strip should be turned from one edge to another. With a decrease in curvature, the impact force is also reduced.

Editing of strips bent to the edge is carried out by straightening. In such cases, strong blows are applied with the toe of a hammer for the purpose of one-sided stretching (lengthening) of the bending points; strikes with a striker should be applied from stretching points on the plane to the edges of the strip or workpiece.

Straightening strips with a twisted (spiral) bend is recommended to be done by unwinding. Such a workpiece is clamped in a vise and untwisted with a hand vise and a lever. Finish editing on a plate or on an anvil with light blows of a hammer.

More rational is editing with the help of special devices.

The straightening of a thin steel strip bent along the edge is carried out in a different sequence: the curved strip is placed on the plate and, pressing it with the left hand, the right hand strikes with a hammer in rows along the entire length of the strip, gradually moving from the lower edge to the upper. At first, the blows should be strong, and as you move to the upper edge, they should be weaker, but more often applied. With this method of straightening (straightening), the lower edge is extended more than the upper one, and the strip becomes even.

The elimination of irregularities after editing is checked by eye, and more precisely, on a marking plate along the clearance or by applying a ruler to the strip.

Sheet metal straightening is a more complex operation. It depends on the type of deformations that acted on the sheet metal in the process of rolling, cutting blanks, electric gas cutting, punching, etc.

All sheet deformations can be divided into three types. The first type of deformation includes bulges and dents in the middle of the sheet or workpiece. The second type of deformation is characterized by waviness of the edges and edges of the sheet. The third type of deformation includes both bulges and waviness of the edges of the sheet and workpieces. This type of deformation is called mixed, or complex. Depending on the type of deformation, the editing of the sheet has its own characteristics.

Editing a sheet with bulges is carried out in the following way. The sheet is placed on the plate with the bulge up and the bulge is circled with chalk.

Rice. 2. Editing thin sheet steel: a-bands (arrows indicate the direction of blows, and dots indicate the density and strength of blows with a hammer); b and c-sheet steel; d and b-methods of editing with mallets and trowels

The edges of the sheet will touch the plate. Then, supporting the sheet with the left hand, the right hand strikes with a hammer from the edges of the sheet towards the bulge. On fig. 64b, as an example, the schemes of striking are shown, and the arrows indicate their direction. Under the action of such impacts, the flat part of the sheet adjacent to the plate will be stretched, and the bulge will gradually straighten.

If there are several bulges on the sheet, then blows should be applied in the intervals between the bulges. As a result, the sheet is stretched, and all the bulges are reduced to one common one, which is straightened in the above way.

It must be remembered that if a sheet with a convex edge does not adjoin the plate, then it should be pressed either by hand or by placing a load on the convex part of the sheet. If you do not do this and strike with a hammer on a sheet that is not tightly adjacent to the plate, then it will have many dents, but drawing metal along the edges of the sheet will not work. At the same time, the dressing time increases, noise is created, tiring the worker.

Having straightened the sheet on both sides, you should see how much the bulge has decreased. If it is still significant, then it is necessary to repeat the blows in the same order, but with less force until straightness is obtained throughout the sheet.

Editing a sheet that has a deformation in the form of waviness along the edges, but with an even middle, is shown in Fig. 2, in. Before editing, putting the sheet on the plate, some kind of load is placed on one of its wavy edges, while the other is pressed against the plate by hand. This position is saved when editing the sheet. From the impact of impacts, the sheet in the middle part will be stretched and the waves along the edges of the sheet will begin to disappear. After that, the sheet should be turned over and continue editing in the same way until the required straightness is obtained.

Editing of thin sheets is carried out with wooden mallets; very thin sheets put on a right slab and smooth with trowels.

The most productive method of straightening sheet metal is straightening on rotary sheet straightening machines. The essence of this process lies in the fact that the sheets or parts to be straightened are passed between two rows of rolls arranged in a checkerboard pattern. The machine has paired input guide rolls arranged one below the other and paired exit guide rolls. The speed of rotation of the input guide rolls is slightly less than that of the output rolls, due to which, in addition to straightening, the sheet is also subjected to slight stretching, which also contributes to the alignment of the workpieces.

Dressing speed from 3 to 6 m/min. with sheet metal thickness from 0.6 to 3 mm. Sheet editing

metal is also produced on three-, five-, seven- or more roll machines.

Straightening of bar metal with a diameter of up to 20 mm and a length of up to 3 m is usually carried out with a bench hammer on a plate. The straightening process in this case is reduced to striking with a hammer on the convexity of the bar placed on the plate, checking the straightness by eye and the gap between the plate and the bar. In the process of dressing, the bar should be rotated around its axis all the time. Long bars are straightened on special roller straightening machines.

Shafts and round blanks up to 35-40 mm in diameter are better and safer to straighten on a manual screw press between two prisms. In this case, the shaft is mounted on the prisms of the press table with the convex side up. The distance between the prisms is adjustable within 150-300 mm. Editing is carried out by pressing the screw (or punch) on the convex part of the shaft. The deflection value is determined here in the centers using an indicator.

Rice. Fig. 3. Scheme of straightening curved shafts on a manual screw press: a-example of straightening; b-control of editing by the indicator; in-device for straightening

On fig. 3, e shows a diagram special device for straightening shafts in the centers. The device consists of grippers, which, depending on the location of the curvature of the shaft, can move along the rocker arm and be fixed with screws. In the center of the rocker is a screw with a prismatic tip. When straightening the shaft, the device is installed so that the prismatic tip is against the place of greatest curvature, then it is pressed with screw 5 until the required shaft deflection is obtained.

Shafts of large cross section with a significant deflection are preheated at the deflection points, after which they are corrected with the help of devices.

In some cases, hardened parts or tools are deformed. The cause of deformation (warping) is the internal stresses created by the rapid cooling of parts in the quench liquid. To eliminate the curvature of such parts, they are subjected to editing.

Depending on the nature of the edit, various hammers are used: when editing parts or tools on which traces of hammer blows are unacceptable, soft hammers (made of copper, lead) are used. When editing, associated with significant deformation of the hardened part, they use a bench hammer weighing from 200 to 600 g or a special straightening hammer with sharp heads. The dressing plate must have a smooth, polished surface. The warped part is placed on the slab with the bulge down, tightly pressing it with the left hand to the slab and holding it by one end, and light, but frequent and accurate blows are applied with the toe of the hammer in the direction from the center of the concavity to its edges. Thus, stretching of the upper metal fibers on the concave side of the part and its straightening is achieved.

Edit details more complex shape, for example, a square, in which, after hardening, the deformation caused a violation of the perpendicularity of the sides, is produced as shown in Fig. 66. If the square has an angle of less than 90 °, then it must be edited At the top inner corner, and if the angle is greater than 90 °, then the straightening of the square should be carried out at the top of the outer corner. are finishing

editing when the edges of the square will accept correct form and both angles will be 90°.

In the case of warping of parts or tools along the plane and along a narrow edge, they should be edited separately: first along the plane, and then along the edges.

Rice. 4. Techniques for straightening (straightening) hardened products: on the straightening headstock; 6 and in-editing the square (hatching indicates the places of impact)

It should be noted that precise parts and tool blanks that have been straightened under a cold press or hammer must be subjected to repeated tempering to relieve stress.

The curvature of the parts is checked by eye (Fig. 82, a) or by the gap between the plate and the part laid on it. The edges of the curved places are marked with chalk.

When editing, it is important to choose the right places to hit. The force of impacts should be commensurate with the amount of curvature and gradually decrease as you move from the greatest bend to the smallest. Editing is considered complete when all irregularities disappear and the part becomes straight, which can be determined by applying a ruler. Editing is done on an anvil correct plate or reliable linings, excluding the possibility of parts slipping from them upon impact.

Editing of strip metal is carried out in the following order. On the convex side, the boundaries of the bends are marked with chalk, after which on left hand they put on a mitten and take a strip, and: they take a hammer in their right hand and take a working position (Fig. 82.6).

The strip is placed on a regular slab so that it lies flat on the slab with a convex upwards, touching at two points. Impacts are applied to the convex parts, adjusting the impact force depending on the thickness of the strip and the magnitude of the curvature; the greater the curvature and the thicker the strip, the stronger the blows. As the strip is straightened, the impact force is weakened and the strip is often turned from one side to the other until it is completely straightened. With several bulges, first straighten those closest to the ends, and then located in the middle.

The results of editing (straightness of the workpiece) are checked by eye, and more precisely, on a marking plate along the clearance or by applying a ruler to the strip.

Metal dressing round section. After checking by eye on the convex side, the boundaries of the bends are marked with chalk. Then a bar is placed on a slab or anvil (Fig. 83) so that the curved part is convex upwards. Hammer blows are applied on the convex part from the edges of the bend to the middle part, adjusting the impact force depending on the diameter of the rod and the size of the bend. As the bend is straightened, the impact force is reduced, finishing with light blows and turning the bar around its axis. If the bar has several bends, first those closest to the ends are corrected, then those located in the middle.

Sheet metal dressing is more complex than previous operations. Sheet material and blanks cut from it may have a wavy or bulged surface. On workpieces that have waviness along the edges (Fig. 84, a), wavy areas are first outlined with chalk or a soft graphite pencil. After that, the workpiece is placed on the plate so that the edges of the workpiece do not hang down, but lie completely on the supporting surface, and, pressing it with your hand, begin editing. To stretch the middle of the workpiece, hammer blows are applied from the middle of the workpiece to the edge, as indicated in Fig. 84, in circles. Circles of smaller diameters correspond to smaller strokes, and vice versa.

Stronger blows are applied in the middle and reduce the force of the blow as you approach its edge. In order to avoid the formation of cracks and work hardening of the material, it is impossible to apply repeated blows to the same place of the workpiece.

Particular care, attention and caution are observed when straightening blanks from thin sheet material. They apply light blows, since with an incorrect blow, the side faces of the hammer can either pierce the sheet blank or cause the metal to be drawn out.

When straightening workpieces with bulges, warped areas are identified, and it is established where the metal is more bulging (Fig. 84.6). The convex sections are outlined with chalk or a soft graphite pencil, then the workpiece is placed on the plate with the convex sections up so that its edges do not hang, but lie completely on the supporting surface of the plate. Editing begins from the edge closest to the bulge, along which one row of hammer blows is applied within the limits indicated on the surface covered with circles (Fig. 84, d). Then they strike on the second edge. After that, a second row of blows is applied along the first edge and again they go to the second edge, and so on until they gradually approach the bulge. Hammer blows are applied often, but not strongly, especially before the end of the edit. After each impact, its impact on the workpiece at the site of impact and around it is taken into account. Do not allow several blows to the same place, as this may lead to the formation of a new convex area.

Under the blows of the hammer, the material around the convex place is pulled out and gradually leveled off. If there are several bulges on the surface of the workpiece at a small distance from each other, with hammer blows at the edges of individual bulges, these bulges are forced to connect into one, which is then ruled by blows around its borders, as indicated above.

Thin sheets are ruled with light wooden hammers (mallets - Fig. 85, a), copper, brass or lead hammers, and very thin sheets are placed on a flat slab and smoothed with metal or wooden blocks(Fig. 85,b).

Editing (straightening) of metal

Straightening (straightening) of hardened parts. After hardening, steel parts sometimes warp. The straightening of parts that are bent after hardening is called straightening. The straightening accuracy can be 0.01 - 0.05 mm.

Depending on the nature of the straightening, hammers with a hardened head or special straightening hammers with a rounded side of the head are used. In this case, it is better to place the part not on flat plate, but on the straightening headstock (Fig. 86, a). Impacts are applied not on the convex, but on the concave side of the part.

Products with a thickness of at least 5 mm, if they are not hardened through, but only to a depth of 1-2 mm, have a viscous core, so they are straightened relatively easily; they need to be straightened as raw parts, i.e., strike at convex places.

Editing a hardened square, in which the angle between the flanges has changed after hardening, is shown in fig. 86.6-g. If the angle has become less than 90 °, then hammer blows are applied at the top of the inner corner (Fig. 86.6 and d on the left), if the angle has become more than 90 °, blows are applied at the top of the outer corner (Fig. 86, c and d on the right).

In the case of warpage of the product along the plane and along a narrow rib, straightening is performed separately - first along the plane, and then along the rib.

Editing of short bar material is carried out on prisms (Fig. 87, a), regular plates (Fig. 87.6) or simple linings, striking with a hammer on convex places and curvatures. Having eliminated the bulges, straightness is achieved by applying light blows along the entire length of the bar and turning it with the left hand. Straightness is checked by eye or by the gap between the plate and the bar.

Strongly springy and also very thick workpieces are dressed on two prisms, striking through a soft pad to avoid nicks in the workpiece. If the forces developed by the hammer are insufficient for straightening, manual or mechanical presses are used.

Editing shafts (up to 30 mm in diameter) on hand presses (Fig. 88, a) is performed as follows. Shaft 2 is placed on prisms 4 and 5, and the pressure is carried out with a screw 3. The deflection value is determined here in centers 7 using indicator 6 (Fig. 88.6).

To eliminate residual stresses in the places of straightening, the responsible shafts are slowly heated for 30 - 60 minutes to a temperature of 400 - 500 ° C and then slowly cooled.

Hardening is done by laying a curved shaft on a flat slab with a bulge down and applying frequent and light blows to the surface of the shaft with a small hammer (Fig. 89, a). After the appearance of a work-hardened layer on the surface (Fig. 89.6), the gap between the shaft and the plate disappears, and the dressing is stopped.

Editing by heating method (impactless). Profile metal (corners, channels, tees, I-beams), hollow shafts, thick sheet steel, forgings are corrected with heating of a curved place (bulge) blowtorch or welding torch until cherry red; the metal layers surrounding the bulge are cooled with raw asbestos or wet ends (rags) (Fig. 90).

Since the heated metal is more ductile, when cooled by a jet compressed air the heated area contracts and the metal straightens.

During processing, storage or use metal parts and blanks may lose their original shape.

For subsequent operations, dimensions and shape finished product it is important that the configuration and dimensions of the workpiece match the design values. This is achieved in the intermediate preparatory operation metal straightening. The operation is carried out on a cold part or it is heated for the purpose of plasticity.

The sheet blank may be wrinkled, having cylindrical shape- twist. Shafts and axles can bend.

What is metal straightening?

The process of returning a metal blank to its original shape is called metal straightening. Defects are as follows:

• Wave.
• Dent.
• Convex.

And also some others.

Types of metal straightening

The operation is divided into two subspecies:

• Manual.
• Machine.

Manual editing and straightening of metal is used in home workshops and in the manufacture of unique products. The set of tools is simple, but a high qualification of a worker - a straightener is required.

Machine straightening is used in industry. The equipment is massive and complex, but has high productivity and process automation capabilities. In addition, the operation of machine straightening is often combined with bending and cutting of sheet blanks, including it as part of a single technological complex.

The operation can be carried out at room temperature. Work at a temperature of 0C and below is unacceptable - the material loses its plasticity and becomes brittle. Sometimes the workpiece has to be heated to 140-400C in order to increase plasticity.

Sheet metal dressing

The complexity of the sheet metal straightening operation also depends on the type of defect.

The most difficult cases are the combination different types defects, for example, waviness of the edge and a bulge in the center of the sheet at the same time.

Convex

The bulge is ruled by strokes around the circumference, starting from outside defect and gradually reducing the radius of the circle, moving from the edge to the center of the defect. The force of the blows becomes less, and the frequency increases.

If there is more than one bulge on the workpiece, they should be combined into one large one. It is necessary to beat between local defects, achieving their association, and then proceed as described above.

Wavy edges

Editing of sheet metal with wavy edges is carried out starting from the edges of the sheet and gradually moving towards its center. After stretching the workpiece in the middle, the waviness of the edges is smoothed out.

Thin sheets

Workpieces of small thickness cannot be straightened with dies due to the high probability of ruptures and creases.

For editing sheet metal use extended surfaces of metal or wooden trowel bars. The workpiece is smoothed with different sides gradually increasing the pressure.

Periodically it is necessary to turn the strip over so that there is no bulge in the other direction. If there are several bulges at the beginning, straighten the ends of the strip, and then move on to the middle.

Soft strikers are not used for straightening. They are made from a high strength alloy and are round shape or round the sharp side.

To straighten the hardened metal, blows are directed along the concave section of the part. As the material stretches on the concave side, the workpiece will straighten out. The operation is carried out on a hemispherical straightening headstock, along which the part is gradually moved up and down.

To straighten a hardened square with a violation right angle developed two approaches. If the corner has become sharp, strikes are directed near the inner corner. If the angle has become obtuse, the blows are directed to the zone at the top outer corner. The material in the affected area is stretched and the right angle is restored.

The method is similar to working with a strip. Irregularities are marked with chalk, the workpiece is located with a bulge up. Impacts are directed from the periphery of the defect to its center.

When the main defect is corrected, the impact power is reduced and the part is rotated around the longitudinal axis in order to avoid deformation in the other direction. Square and rectangular rolled products are corrected in the same way.

Here, the spin method is used. One end of the spiral is fixed in a vice fixed on the correct plate, the other in a manual clamp.

After partial untwisting of the spiral, it is pressed against the plate and corrected like a round rolled product, determining the curvature through the light.

The main methods of straightening metal

The choice of method is influenced by the nature and area of ​​the section, the brand and type of alloy, the size of the defect relative to overall size products.

Depending on the method of applying stresses in metal blanks, there are three ways of straightening metal:

• cold bending;
• stretching in a cold state;
• local heating.

Heating is carried out gas burners or by induction.

What is the purpose of metal cutting?

The configuration of a part can be changed during its primary processing, transportation or storage. Such blanks are unsuitable for further use, but are not irrevocable, final marriage. Metal dressing is used in order to return the form to the workpiece, determined by the design and technological documentation.

Sometimes, in order to reduce the cost of production, the enterprise deliberately acquires blanks of improper shape, in this case the operation is included in technological process. Planned editing of metal can also be included in the process after heat treatment operations that cause a change in the shape of the part. Otherwise, the work will be unscheduled, and its cost is included in unplanned losses.

Straightening equipment

The basis of any set of tools is the right stove. It must be perfectly even, massive and stable, for which it is cast from high-impact cast iron or steel, to strengthen the structure, it is provided with longitudinal and transverse stiffeners. They are installed on a massive concrete base.

Dressing hammers should be softer than the workpiece material. Therefore, they are supplied with wooden or rubber strikers. To work with steel sheets soft-faced hammers made of copper or lead are used. The striker must have a rounded shape. A square-shaped striker is not suitable, as it will leave characteristic traces on the sheet blank - nicks. The mass of the plate should be related to the mass of the hammer approximately 100:1.

To work with a sheet blank, a lining plate made of dense rubber is also used, with a large number of tubercles of the same height formed on it. Under impact, the metal finds its place on its own, and the productivity of the process is noticeably increased compared to a bare steel straightening plate.

To work with thin sheets, special equipment is used - trowels and supports. To work with hardened parts, cylindrical or hemispherical straighteners are used.

In the home workshop, an anvil or a massive metal plate is used.

The enterprises use special mechanized straightening complexes with mechanical sheet feeding and automated correction of defects. In some, the billet is pulled between massive counter-rotating rolls. In others, the operation takes place on the correct platen by lowering a wide press.

In his practical work a locksmith is often faced with the editing of metal of a particular profile or with the editing of blanks.
Editing is a preparatory operation. It can be done in two ways: mechanically- using correct rolls, presses and various devices and manual - using a hardened steel hammer, sledgehammer, anvil or plate and auxiliary tool- ironers.
When manually straightening, it is better to use a hammer with a round face to prevent nicks and dents on the surface of the straightened workpieces. The surface of the hammer head must be carefully sanded.
To straighten parts with a finished surface, as well as thin steel products or workpieces made of non-ferrous metals and alloys, hammers are used. soft materials- copper, brass, lead, wood.
When straightening thin wire and thin strip and sheet metal, metal and wooden mandrels, floats and gaskets are used.
Editing of strip and sheet material. When editing a curved strip, the latter is held with the left hand and, on an anvil or plate, strikes with a hammer at the convex places of the wide side of the strip, turning the strip from one side to the other as necessary.
The impact force is adjusted depending on the magnitude of the curvature and the thickness of the strip.
After finishing the editing of the wide part of the strip, they begin to edit the edge, first with strong blows, and then with weak ones, turning the strip after each blow from one edge to another.
Checking the straightened strip is done by eye, and more precisely - with a ruler or on a marking plate.
Editing of thin strip steel is carried out in a different way, since from hammer blows on a convex rib, a thin strip will bend to the sides, and the places in contact with the plate will stick together.
A thin strip is corrected on a plate: pressing it with the left hand, with the right hand strikes with a hammer along the entire length of the strip, gradually moving from the lower edge to the upper one, as indicated in Fig. 69.

In the beginning, the blows should be strong, and as you move to the upper edge, they should be weaker, but more often applied. Such editing helps to stretch the lower edge, and the strip becomes even.
Editing sheet material is a more complicated operation, since the bulges on the sheets in most cases are in the middle or are scattered over the entire surface of the sheet, and when you hit the convex parts with a hammer, the latter will not only not decrease, but even increase in size.
Therefore, editing sheet material should be carried out as follows:
The sheet is placed on the stove and the bulges are outlined with chalk or pencil. While supporting the sheet with the left hand, the right hand strikes with a hammer from the edge of the sheet towards the bulge, as shown in Fig. 70 arrows. Blows should be applied frequent, but not strong. Under the influence of such blows, the flat part of the sheet will increase, and the bulge will gradually straighten.

As you approach the convexity, the blows should be made more often and weaker, at the same time it is necessary to monitor whether the surface of the sheet improves, whether there are traces of hammer blows on it and whether the convexity is eliminated.
If there are several bulges on the sheet, then blows should be applied in the intervals between the bulges, as a result of this, the sheet is stretched and all the bulges are reduced to one common bulge, which is straightened in the usual way, i.e. going from the edges of the convexity to the middle. After that, the sheet is turned over and with light blows of the hammer, its straightness is finally restored.
Very thin sheets are leveled on a flat and smooth plate.
Straightening of bar material and shafts. Long rods and wires are straightened by passing through dies in broaching machines or through rotating rollers in a special straightening machine, or by hand on a plate. Short workpieces are also ruled in this way. Checking the straightness of bars and blanks is carried out on the plate or by eye.
Shafts and workpieces of large cross section are straightened on a manual or mechanical press, for which the shaft or workpiece is installed on the prisms of the press table with the convex part up. The distance between the prisms is adjustable.
Usually it fluctuates between 150 - 300 mm. Editing is carried out by pressing the screw on the convex part of the shaft.
Shafts of large cross-section and with a significant deflection are preheated in places of maximum deflection.
Checking the shaft after dressing is carried out in centers mounted on a separate table or plate, as indicated in Fig. 71.

Editing hardened parts. Warped steel parts or blanks after hardening are ruled by special steel hammers, the impact part of which has the shape of a metalworker's hammer, carefully processed, without sharp corners and well hardened. The dressing plate must have a smooth ground surface (flat or convex), the hardness of which must not be lower than the hardness of the hammer head.
Hammer blows should be applied not to the convex part of the hardened part, but to the concave part. In this case, the blows should not be strong, but frequent.
For example, let's take a look at several cases of straightening hardened parts.
The part is placed on the convex surface of the plate and, holding it with the left hand, apply light but frequent hammer blows to the concave part, starting from the most concave part and gradually moving to the place where the deflection ends.
At the same time, the part is turned by 15 - 20 ° with the left hand, either in one direction or the other, and moved towards itself. Thus, the impacts are distributed over the concave surface of the sector with an angle of 30 - 40°.
As a result of this, the fibers of the concave part of the part seem to be distributed, stretched from hammer blows, and in the convex part they are compressed and the part is leveled.
In a similar way, the hardened strip of the ruler is corrected (Fig. 72).

In the case when a flat part has cutouts, for example, a bracket, a template, then it warps during hardening (both along the plane and along the edge), and therefore editing should be carried out in the following sequence:
The template is placed with the convex part on the plate and held with the left hand at one end, and with the right hand, frequent, but not strong blows are applied to the concave part with the toe of the hammer, starting from the middle and gradually moving to the edge. Then, taking the opposite end of the template with your left hand, continue editing the second part of the template in the same sequence.
After editing the plane, they start editing along the edge. In this case, the template or bracket is pressed against the plate with the left hand, and the right hand strikes with the toe of the hammer from the side of the concave part from the middle to the edge alternately on both sides (Fig. 73).

Dressing hardened rollers and spindles with a diameter of 20 mm and above usually produce hand press by pressing the press screw on the convex part of the part.

Study guide for preparation
workers in production

Locksmith workshop

Straightening of strip metal bent along a plane

The flattening exercise is usually performed on a cast iron or steel plate using a variety of hammers. For straightening cleanly processed steel strips and non-ferrous metal strips, wooden hammers, hammers, with soft inserts (copper, lead, aluminum) and steel hammers, striking wooden or soft metal pads with them.

When straightening and bending metal, it is better to use a hammer with a round, well-polished striker, striking with the central convex sphere of the striker (Fig. 52). Hammers with a square head are not recommended, since during strikes on metal, traces in the form of nicks may remain from its corners.

Rice. 52. Dressing with a hammer with a spherical head

Editing along the plane is performed in the following sequence.

1. The convex parts of the strip are determined by eye (Fig. 53), marking their boundaries with chalk.

Rice. 53. Checking the results of editing by eye

2. A mitten is put on the left hand. They take a hammer in the right one, strip steel in the left one and take the working position. Stand when editing should be straight, free and stable.

3. The strip is placed on the correct plate with a bulge upwards, with contact in two places (Fig. 54), since with a loose fit at the moment of a blow with a hammer, recoil to the left hand is possible.

Rice. 54. Acceptance of straightening a steel strip on a plane

4. Hammer blows are applied along the edges of the convex parts, gradually approaching the middle of the bend. It is necessary to adjust the impact force depending on the thickness of the strip and the magnitude of the curvature; the greater the curvature and the thicker the strip, the stronger the blows should be. As the strip is straightened, the force of blows should be weakened and the strip should be turned more often from one side to the other until it is completely straightened; when striking with a hammer, you should look only at the place of impact.

If there are several bulges, then first straighten the extreme ones, and then the bulges located in the middle of the strip.