Straightening of steel sheet. Correct hydraulic presses for straightening - straightening shafts, axles, pipes. The main methods of straightening metal

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 carried out on a plate or reliable linings, which exclude the possibility of the part slipping on impact. manual and machine straightening metals should be produced in mittens.

The curvature of the parts is checked by eye or by the gap between the plate and the part laid on it. Curved places are marked with chalk.

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.

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 a metal bent along a plane (Fig. 44, a). This type of editing is the most common; it is usually performed without much difficulty. It is more difficult to straighten metal bent along an edge (Fig. 44, b). 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, i.e., straightening. Even more difficult is the straightening of twisted strips (Fig. 44, c).

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. The curved strip is placed on the plate with the curved part up and, holding it with the left hand, with the right hand, strong blows are applied with a hammer to the convex places, 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 be periodically rotated from one side to the other as necessary. Having straightened the wide side, proceed to

Editing the edges 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 should be 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 bend is recommended to be done by unwinding. Such a workpiece is clamped in a vise and untwisted with a lever or hand vise. Finish editing on a plate or on an anvil with light blows of a hammer.

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. In the beginning, 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 a ruler superimposed on the strip.

Sheet metal straightening is a more complex operation. It depends on the type of deformations that acted on the sheet metal during rolling, cutting into dimensional 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 stove with a bulge up and circled with chalk. 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. Under the action of such blows, the even 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 the 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 one, which is straightened in the manner indicated above.

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 performed in a similar way. 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 thin sheets is carried out with wooden hammers - mallets (Fig. 45, a); very thin sheets are placed on a regular plate and smoothed with trowels (Fig. 45, b).

Straightening of short bar metal with a diameter of up to 30 mm and a length of up to 3 m is usually carried out with a bench hammer on a straightening (straightening) plate. The straightening process in this case is reduced to striking with a hammer on the bulge of the bar placed on the plate, and checking the straightness by eye and by 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.

Straightening (straightening) of hardened parts. After hardening, steel parts sometimes warp. In some cases, parts or tools that have been hardened undergo deformations. The cause of deformation (warping) are internal stresses, created by rapid cooling of parts in the quench liquid. To eliminate the curvature of such parts, they are subjected to editing. Editing hardened parts is called straightening. The straightening accuracy can be 0.01-0.05 mm.

Depending on the nature of the edit, various hammers are used: when straightening parts or tools on which traces of hammer blows are unacceptable, soft hammers (made of copper, lead) are used. When straightening, associated with a significant deformation of the hot part, use a bench hammer weighing from 200 to 600 or a special straightening hammer with sharp strikers (Fig. 46, a). The plate for editing (straightening) should 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, light, but frequent and accurate blows are applied with the toe of the straightening hammer in the direction from the center of the concavity to its edges. This achieves stretching of the upper metal fibers on the concave side of the part and its straightening.

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

Editing (straightening) of parts of a more complex shape, for example, a square, in which, after hardening, the deformation caused a violation of the perpendicular

These sides are produced as shown in fig. 46. ​​If the square has an angle of less than 90 °, then it should be straightened at the top inner corner(Fig. 46, 6) 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 (Fig. 46, c). They finish straightening the square when its edges take correct form and both angles will be 90°

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

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

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 efforts developed by the hammer are insufficient for dressing, use manual or mechanical presses.

Heated edit. 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 to cherry red; the layers of metal surrounding the bulge are cooled with raw asbestos or wet ends.

The original rolled metal, both sheet and bulk, does not always have flatness indicators sufficient for the qualitative performance of subsequent deformation operations. In such cases, metal straightening is used as a preliminary operation. A related term - metal straightening - is a type of this operation, as a result of which only the axis of the bar is aligned.

State standards the following types of tolerances for the shape of finished rolled products are stipulated:

1. For bars of round and square cross-section - spatial curvature and apparent twist
2. For bars square section, in addition - concavity and convexity of the faces;
3. For steel strips - non-flatness, crescent, bulge of the side faces.
4. For sheets - non-flatness.
5. For tapes and rolls - telescopicity and rib curvature.

In the case of high-precision stamping, all of the above defects provoke accelerated wear of the dies, and the accuracy finished products decreases. The reason for such distortions can also be separating operations on sheet and section shears, when the edges of the sheet / strip or the ends of the bars are unacceptably curved.

Even more prerequisites for straightening hot stamping. Finished forgings are bent when:

• Pushing out of the cavity of the die stream (especially often this happens with forgings complex shape);
• Heat treatment, after which internal residual stresses arise in the metal;
• Trimming flash due to uncontrolled shrinkage of the metal.

In cold stamping technologies, metal straightening is performed after bending parts made of high-carbon or spring steels, as well as during cold extrusion of products with a long core part. It is also quite common to straighten and straighten metal in the form of a roll before dissolving it into tapes.

The basis for including such an operation in technological process production are the results of measurements of the shape of parts, for which either special templates or a universal measuring tool are used. With minor deviations, manual straightening of the metal is sometimes acceptable, but in most cases this is not enough.

Varieties of metal editing

The operation in question can be performed cold or hot. In the hot state, forgings are straightened, which have already gone through all the transitions of deformation, including cutting off the flash. In this case, they do not provide for a separate operation, but deform the cutting press stamp in the final stream (although in justified cases hot dressing metal can also be made on the main stamping equipment). The advantages of such processing are considered to be lower energy consumption, as well as a beneficial effect on the structure and operational properties forging material.

Cold straightening in hot stamping is applied after the stamped products have undergone heat treatment. The tool for performing such an operation is very simple, and according to the configuration of the working cavity, it fully corresponds to the dimensions of the forging, which are shown on its drawing. The operation is often performed simultaneously in two planes, which improves the quality finished product.

In sheet stamping, editing is performed:

• After cutting-punching of thick sheet metal, when the cutting of the fibers of the metal of the workpiece leads to the occurrence of internal stresses;
• After free bending (especially without clamping), to remove defects in the shape of the workpiece that arose due to springback;
• When stamping outright, when the curvature metal billet occurs due to intense friction of the product on the matrix;
• After multi-pass drawing of parts with flanges.

In cold sheet forging, there are reductions with smooth, point and waffle dies. In the first case, flat surface calibration is carried out; therefore, this method is effective for thin-sheet blanks made of highly ductile metals. Specific forces do not exceed 100 MPa, and there are no tool prints on the surface of the finished product.

For blanks with thicker, as well as from metals of increased hardness, it is necessary to perform spot / waffle straightening. On the working tool, small notches are made in the form of teeth, and their points on the punch and the matrix should not coincide. In this case, the specific effort is higher - up to 250 ... 300 MPa, but as a result, all surface defects are corrected.

Sometimes flat straightening is done before rolling. The original sheet or strip of metal is rolled through several regular rollers (their number must always be unpaired, and the number of upper, pressure, rollers is always one more than the lower, support ones).

Straightening equipment

If these transitions are combined with the main deformation operations (as is often the case with hot stamping), then no special equipment is required. Cold straightening of metal bars or strips is performed on. They are horizontal machines that operate on the principle of rotary forging.

The difference lies in the fact that the pressures created by the working rollers must not exceed the plasticity limit of the straightened material. Such machines operate in automatic mode, and therefore are characterized by high productivity. The rods are edited similarly, only the profile of the working rollers in this case is not flat, but corresponding to the cross section of the source material.

It is possible to straighten blanks that are voluminous in terms of presses. If the specific force does not exceed 300 MPa, then screw presses with an arc-stator drive of the F17__ series are used. The effect is achieved through high speed collision of a flat die (attached to a slider) with a product that requires straightening. Since the distribution of pressure over the entire surface is the same, then simultaneously on working plate there may be several of the same overall dimensions details. This reduces the complexity of the operation.

The most difficult and responsible is the editing of parts after cold extrusion. Since the strain hardening of the material in this case is very large, the specific forces can reach the plasticity limit, i.e. 600 ... 800 MPa and even more. The impact nature of the load created by the screw press does not provide the proper quality of dressing due to the inertia of the material. Therefore, special presses of the K82__ and K83__ series with a crank-knee working mechanism are used. A feature of the scheme of such a press is the ability to hold the part (up to 2 ... 3 s) under pressure at the lowest position of the equipment slider. As a result, internal stresses are overcome and the part is aligned.

Edit- This is an operation to straighten a bent or warped metal, which can only be subjected to ductile materials: aluminum, steel, copper, brass, titanium.

There are two types of metal straightening: cold straightening and hot straightening. Editing is carried out

On special right slabs which are made of cast iron or steel.

edit small parts can be crafted on blacksmith anvils. Edit

metal is carried out with hammers of various types depending on the condition

surface and material of the part being dressed.

When dressing workpieces with a raw surface, hammers are used with

round strikers weighing 400g. A round head leaves fewer marks on the surface than a square one.

When dressing workpieces with a treated surface, hammers are used that have strikers with soft inserts (made of copper, aluminum), which do not leave marks on the surface. When editing sheet material they use wooden mallets, and very thin sheets are ruled by wooden or metal bars - trowels.

Editing is carried out in several ways: bending, stretching and smoothing.

Editing by bending used for straightening round (rods) and shaped material, which

have a fairly large cross section. In this case, hammers with steel heads are used. The workpiece is placed on the correct plate with the bend upwards and blows are applied to the convex places, bending the workpiece in the direction opposite to the existing bend. As the workpiece is straightened, the impact force is reduced.

Pull edit used when straightening sheet material having bulges

or waviness. Such editing is carried out with hammers with soft metal strikers or mallets. In this case, the workpiece is placed on a regular plate with the bulges up and frequent light blows are applied, starting from the border of the bulge, towards the edge of the workpiece. The strength of the blows gradually decreases. In this case, the metal is stretched to the edges of the workpiece and the bulge is straightened due to this stretching.

Editing by smoothing used in cases where the workpiece has a very small thickness. Smoothing is carried out with wooden or metal bars. The workpiece is smoothed on the correct plate, pulling the material with the help of trowels from the edge of the unevenness to the edge of the workpiece, and by pulling the material, the surface of the workpiece is leveled.

Tools and fixtures used in editing

Correct slabs made of gray cast iron with working surfaces

1.5×5.0; 2.0×2.0; 1.5×3.0; 2.0×4.0m. On such plates, profile blanks are corrected and

blanks from sheet and strip material, as well as bars from black and non-ferrous

Leveling grandmas used for straightening workpieces made of

high hardness metals or pre-hardened metals.

Leveling headstocks are made from steel billets with a diameter

200..250mm, their working part has a spherical or cylindrical shape.

Hammers when editing, they are used to apply force

effort at the place of editing. Depending on the physical and mechanical

properties of the workpiece to be processed and its thickness are chosen

Various types hammers. When straightening blanks from bar and

strip material, hammers with square and round

Soft hammers are used for straightening machined surfaces.

inserts made of aluminum and its alloys or copper.

Sledgehammers are hammers of large mass (2.0 ... 5.0 kg) and

are used for straightening round and shaped rolled products of large transverse

sections in cases where the force of impact applied by a conventional metalwork hammer,

insufficient to straighten the deformed workpiece.

The presence of curvature in the parts is checked by eye, or the part to be edited is placed on the plate and the gap between the plate and the part determines whether there is any curvature. Curved places are marked with chalk.

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 gradually decrease as you move from the largest to the smallest bend. The work is considered finished when all the irregularities disappear and the part is straight, which can be checked by applying a ruler. The straightened part or workpiece must be correctly positioned on the plate. Work should be in gloves.

Editing of strip metal. It is carried out in the following order: the detected bend is marked with chalk, after which the curved part is taken by the end with the left hand and placed on the slab or anvil with the curved part up. AT right hand they take a hammer and strike at the convex places of the wide side, making strong blows on the largest bulge and reducing them depending on the magnitude of the curvature; the greater the curvature and the thicker the strip, the stronger the blows need to be applied, and vice versa, as the strip is straightened, weaken them, finishing with light blows. The force of impacts should be reduced with decreasing size of the spots.

When editing the strip, as necessary, it is necessary to turn from one side to the other, and having finished editing the wide side, proceed to editing the rib. To do this, you need to turn the strip on the edge and apply strong blows at first, and as the curvature is eliminated, weaker and weaker in the direction from the concave shape to the convex one. After each blow, the strip should be rotated from one edge to another.

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

Straightened material may have defects mainly due to incorrect location on which to strike, an uneven decrease in the force of impact; lack of proper accuracy on impact; leaving scratches and dents.

The blanks cut on the machines are usually warped at the edges and have a wavy shape. Editing them is done a little differently. Before editing, the warped places are circled with chalk or a simple graphite pencil. After that, the workpiece is placed on the plate, pressed with the left hand, and with the right hand they begin to strike with a hammer in rows along the entire length of the strip, gradually moving from the lower edge to the upper one. The blows are struck at first strong, and as you move to the upper edge with less force, but more often.

Sheet metal straightening. This is a more complex operation. The bulges formed on the workpieces are most often scattered over the entire surface of the sheet or are located in the middle, therefore, when straightening workpieces with bulges, it is impossible to strike the convex sheet with a hammer, since this will not only not reduce them, but, on the contrary, will stretch even more (Fig. 93b).

Before you start straightening workpieces with bulges, you need to check and establish where the metal is stretched more. Convex places in the form of bulges circle with a pencil or chalk. After that, lay the workpiece so that its edges lie on the entire surface, and do not hang over. Then, supporting the sheet with the left hand, a series of hammer blows are applied with the right hand from the edge of the sheet towards the bulge.

Strikes as you approach the bulge should be applied weaker, but more often.

Editing thin sheets is done with wooden mallets, and very thin sheets are placed on flat slab and smoothed with trowels.

Editing of bar material. Short rods rule on regular plates, 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.

Highly springy and also very thick workpieces are ruled on two prisms, striking through a soft spacer to avoid gouges on the workpiece. If the force developed by the hammer is not enough to perform editing, then manual or mechanical presses are used. In this case, the workpiece is placed on the prisms with the convex part up and pressed against the curved part.

Straightening (straightening) of hardened parts. After hardening, steel parts sometimes warp. Editing hardened parts is called straightening. Straightening accuracy can be achieved within the range of 0.01 to 0.05 mm.

Depending on the nature of straightening, various hammers are used: when straightening precise parts on which traces of hammer blows are not allowed, soft hammers (made of copper, lead) are used. If during straightening it is necessary to stretch, lengthen the metal, steel hammers weighing from 200 to 600 g with a hardened striker or special straightening hammers with sharp strikers are used.

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

Thin products (thinner than 5 mm) are always calcined through, so they need to be straightened not in convex, but, on the contrary, in concave places. The fibers of the concave part of the part are stretched, elongated by hammer blows, and the fibers of the convex part are compressed and the part is extruded.

On fig. 94 shown straightening a corner. If the square has an acute angle, then you need to straighten it at the top of the inner corner, if it is an obtuse angle, then at the top of the outer corner. Thanks to this straightening, the edges of the square will stretch and it will take the correct shape with an angle of 90 °.

Rice. 94. Techniques for straightening (straightening) hardened parts of squares

In the case of product warping along a plane and a narrow rib, straightening is performed separately: first along the plane, and then along the ribs.

Metal dressing

Editing is used in cases where it is necessary to eliminate the distortion of the shape of the workpiece - waviness, warping, dents, curvature, bulging, etc. The metal can be edited both in cold and heated form. Heated metal is easier to edit, which is also true for other types of its plastic deformation, for example, bending.

At home, dressing should be done on an anvil or a massive plate of steel or cast iron. The working surface of the stove must be flat and clean. To reduce the impact noise, the hob should be installed on wooden table, with which, in addition, it is possible to level the plate so that it is in a horizontal position.

For editing, you need a special locksmith tool. You can’t produce it with any hammer that is at hand, the metal can not only not straighten out, but also get even bigger defects. The hammer must be made of soft material- lead, copper, wood or rubber. In addition, you can not rule the metal with hammers with a square head: it will leave traces in the form of nicks on the surface. The hammer head should be round and polished.

In addition to hammers, wooden and metal trowels and supports are used. They are used for straightening thin sheet and strip metal. For dressing hardened parts with shaped surfaces, there are correct headstocks.

It’s probably not worth reminding that metal straightening (straightening) must be done in work gloves, regardless of whether hard work or not, whether the workpiece is large or small, and whether it is severely warped.

To check the curvature of the workpiece, you need to lay it on a smooth plate with that surface, which, after straightening, should be a plane. The gap between the plate and the workpiece will indicate the degree of curvature that needs to be eliminated. Curved places should be marked with chalk - it is much easier to strike with a hammer than when focusing only on the curvature noticeable to the eye.

Editing of strip metal bent in a plane, is the simplest operation. The curved workpiece must be positioned so that it has two points of contact with the anvil. Hits with a hammer or sledgehammer should be applied to the most convex places and reduce the force of blows as the bulges become smaller. Do not strike only on one side of the workpiece - the metal may bend into reverse side. To prevent this from happening, the workpiece must be turned over from time to time. For the same reason, you should not strike several blows in a row in the same place.

If there are several bulges, you must first straighten the edges of the workpiece, and then its middle.

Editing of round metal. This kind of work is basically similar to straightening strip metal. To do this, mark uneven places with chalk and place the workpiece with the bulge up, apply blows to the convex part from the edges of the bend to the middle of the bulge. When the main curvature is corrected, the force of impacts must be reduced and periodically rotated metal rod around its axis to prevent curvature in the opposite direction.

Metal bars of square section must be edited in the same sequence.

Editing of metal twisted in a spiral, produced by the spinning method. In order to straighten the curvature, you need to clamp one end of the twisted metal into a large vice on locksmith's table, the other - in hand vise. Having untwisted the metal to the extent that can be controlled by eye, you need to continue editing on a smooth, verified plate conventional method, controlling the curvature through the light.

Sheet metal dressing

The complexity of straightening sheet metal depends on what type of defect the sheet has - waviness of the edge, or a bulge, or a dent in the middle of the sheet, or both at the same time (Fig. 15).

Rice. 15. Techniques for straightening sheet metal: a - with a deformed middle of the sheet; b - with deformed edges of the sheet; c - using a wooden trowel; d - using a metal trowel.

When editing the bulge, it is necessary to strike, starting from the edge of the sheet towards the bulge (Fig. 15 a, b).

The most common mistake is that the heaviest blows are applied to the place where the bulge is greatest, and as a result, small dents appear on the bulge area, which further complicates the uneven surface. In addition, the metal in such cases experiences a very strong tensile strain. You need to do just the opposite: the blows should become weaker, but more often, as the edit approaches the center of the bulge. The sheet of metal must be constantly rotated in a horizontal plane so that the blows are evenly distributed over its entire surface.

If the sheet has more than one convex section, but several, you must first reduce all the convexities into one. To do this, strike with a hammer in the intervals between them. The metal between the bulges is stretched, and they are combined into one. Then you have to keep editing. in the usual way. If the middle of the sheet is even, and the edges are distorted by waves, then the sequence of blows during editing should be the opposite: they should be applied starting from the middle, moving towards the curved edges (Fig. 15, b). When the metal in the middle of the sheet is stretched, the waves at its edges will disappear.

Very thin sheets cannot be corrected even with mallets made of soft material: they will not only leave dents, but can also tear thin metal.

In this case, ironing bars made of metal or wood are used for editing, with which the sheet is smoothed on both sides, periodically turning it. The quality of editing can be controlled using a metal ruler.

Anyone who has taken on the straightening of a steel sheet knows that this is a rather difficult job: while straightening one bend, others appear on the sheet. However, this can be avoided and thus significantly facilitate the work. The steel sheet must be laid for straightening not on a smooth plate, as is usually done, but on a backing plate with many small blunt bumps evenly spaced on its surface. In this case, the quality of work should increase, and the labor intensity should decrease. Metal under the blows of a rubber hammer will, as it were, look for its own place. At the same time, barely noticeable waves are formed on the sheet; during puttying and painting, they will begin to fill up and contribute to the fact that the putty and paint will adhere to the metal very firmly. Irregularities after coating the metal are completely invisible. The only difficulty is how to make the required lining plate. It is really difficult to make it at home: tubercles are usually obtained by cutting through smooth plate big number mutually intersecting and closely spaced grooves. You can do this on a planer or milling machine, so if there is such an opportunity, it is better to use it.

Edit hardened metal(straightening)

Soft dressing hammers are unsuitable for straightening hardened metal (straightening). A special hammer with a hardened metal head or with a rounded narrow side is required. You can make a straightening hammer yourself. To do this, it is necessary to make a slot in the narrow head of the hammer and tightly press into it a plate of hard alloy VK6 or VK8, sharpened under a radius of 0.1–0.2 mm.

Hardened metal is corrected by the reverse method: strikes must be applied not to the convex, but to the concave section of the workpiece: it will begin to straighten due to the fact that the metal on the concave side will stretch (Fig. 16).

Rice. 16. Editing of hardened metal (straightening): a - strips; b, c - squares.

Straightening is more convenient to produce not on flat plate, but on a special straightening headstock, which has a convex surface, moving the workpiece up and down along it.

An unsolvable task for an inexperienced locksmith is to edit a flat square, in which the angle has changed and has become more or less than 90 °. Such squares are no longer suitable for checking right angles, and, as a rule, they are thrown away. Meanwhile, the hardened metal square can be straightened. If the right angle has decreased and is less than 90 °, then hammer blows must be applied along the plane of the square at the top of the inner corner. If the angle has increased and exceeds 90°, strikes should be applied at the top of the outer corner.

After the metal is straightened, you can proceed to its further processing.