Markup is an operation by drawing on the surface of the workpiece lines (marks) defining the contours of the part being manufactured, which is part of some technological operations. Despite the high costs of manual highly skilled labor, marking is widely used, including at mass production enterprises. Usually marking work are not controlled, therefore, mistakes made during their implementation are revealed in most cases in finished parts. It is quite difficult to fix such errors, and sometimes it is simply impossible. Depending on the features technological process distinguish between planar and spatial markings.

Plane markings are used when processing sheet material and profiled rolled products, as well as parts on which marking marks are applied in the same plane.

Spatial markup- this is the drawing of scratches on the surfaces of the workpiece, interconnected by mutual arrangement.

Depending on the method of applying the contour to the surface of the workpiece, various tools are used, many of which are used for both spatial and plane marking. Some differences exist only in the set of marking devices, which is much wider when spatial markup.

Tools, fixtures and materials used for marking

Scribblers are the most simple tool for drawing the contour of the part on the surface of the workpiece and represent a rod with a pointed end of the working part. Scribes are made of tool carbon steels of U10A and U12A grades in two versions: one-sided (Figure 2.1, a, b) and two-sided (Figure 2.1, c, d). Scribes are made with a length of 10 ... 120 mm. The working part of the scribe is hardened at a length of 20 ... 30 mm to a hardness of HRC 58 ... 60 and sharpened at an angle of 15 ... 20 °. Risks are applied to the surface of the part with a scribe using a scale ruler, template or sample.

Reismas used for drawing marks on the vertical plane of the workpiece (Fig. 2.2). It is a scribe 2, fixed on upright rack installed on a massive base. If it is necessary to draw marks with a higher accuracy, use a tool with a scale - a height gauge (see Fig. 1.13, d). To set the gauge to a given size, you can use blocks of gauge blocks, and if you do not really need high accuracy markup, then use the vertical scale ruler 1 (see Fig. 2.2).

Marking compasses used for drawing arcs of circles and dividing segments and angles into equal parts (Fig. 2.3). Marking compasses are made in two versions: simple (Fig. 2.3, a), which allows you to fix the position of the legs after setting them to size, and spring (Fig. 2.3, b), used for more accurate setting of the size. To mark the contours of critical parts, use a marking caliper (see Fig. 1.13, b).

In order for the marking risks to be clearly visible on the marked surface, point depressions are applied to them - cores that are applied special tool- punch.

Kerners(Fig. 2.4) are made of U7A tool steel. The hardness along the length of the working part (15 ... 30 mm) should be HRC 52 ... 57. In some cases, center pins of a special design are used. So, for example, for drawing core depressions when dividing a circle into equal parts, it is advisable to use a core punch proposed by Yu.V. Kozlovsky (Fig. 2.5), which can significantly increase productivity and accuracy when applying them. Inside the body 1 of the punch, there is a spring 13 and a firing pin 2. Legs 6 to 11 are attached to the body by means of a spring 5 and screws 12 and 14, which, thanks to the nut 7, can simultaneously move, providing adjustment to a given size. Replaceable needles 9 and 10 are attached to the legs with nuts 8. When adjusting the center punch, the position of the striker with the impact head 3 is fixed by the threaded sleeve 4.

Marking using this punch is carried out in the following sequence:

The tip of the needles 9 and 10 is set at the risk of a previously drawn circle on the workpiece;

Strike the impact head 3, punching the first point;

The body of the punch is turned around one of the needles until the second needle coincides with the marked circle, the impact head 3 is again struck. The operation is repeated until the whole circle is divided into equal parts. At the same time, the marking accuracy increases, since, thanks to the use of needles, the center punch can be adjusted to a given size using a block of gauge blocks.

Punching if necessary center holes it is convenient to use on the ends of the shafts special device for punching - with a bell (Fig. 2.6, o). This device makes it possible to make core grooves on the centers of the end surfaces of the shafts without their preliminary marking.

For the same purposes, you can use a center-finder square (Fig. 2.6, b, c), consisting of a square 1 with a ruler 2 attached to it, the edge of which divides the right angle in half. To determine the center, the tool is placed on the end face of the part so that the inner shelves of the square touch it cylindrical surface and draw a line along the ruler with a scribe. Then the center finder is turned at an arbitrary angle and the second risk is carried out. The intersection of the lines drawn on the end face of the part will determine the position of its center.

Quite often for finding centers at the ends cylindrical parts use a protractor centro-finder (Fig. 2.6, d), which consists of a ruler 2, fastened to a square 3. The protractor 4 can be moved along the ruler 2 and fixed in the desired position using a locking screw 1. The protractor is placed on the end surface of the shaft so that the side shelves of the square touched the cylindrical surface of the shaft. In this case, the ruler passes through the center of the shaft end. By installing the protractor in two positions at the intersection of the marks, the center of the shaft end is determined. If you want to make a hole located at a certain distance from the center of the shaft and at a certain angle, use a protractor, moving it relative to the ruler by a given amount and turning it by required angle... At the point of intersection of the ruler and the base of the protractor, the center of the future hole, which has an offset relative to the axis of the shaft, is screwed.

The punching process can be simplified by using an automatic mechanical center punch (Fig. 2.7), consisting of a body assembled from three parts: 3, 5, 6. Two springs 7 and 11 are placed in the body, a rod 2 with a center punch 1, a striker 8 with a shifting cracker 10 and flat spring 4. Punching is carried out by pressing on the workpiece with the tip of the center punch, while the inner end of the rod 2 abuts against the cracker, as a result of which the striker moves up and compresses the spring 7. Resting on the rib of the shoulder 9, the cracker moves to the side and its edge comes off the rod 2. At this moment, the striker, under the action of the force of a compressed spring, applies along the end of the rod with a center punch swipe, after which the spring 11 restores the normal position of the punch. The use of such a punch does not require the use of a special percussion tool - a hammer, which greatly simplifies the work of applying pits.

For the mechanization of marking work an electric center punch can be used (Fig. 2.8), which consists of a body 8, springs 4 and 7, a striker 6, a coil 5 with a lacquered wire winding, a rod 2 with a center punch 3 and electrical wiring. When pressing the center punch set on the marking risk, electrical circuit 9 closes and current flows through the coil, creating a magnetic field. At the same time, the drummer is instantly drawn into the reel and strikes the rod with a center punch. During the transfer of the punch to another point, the spring 4 opens the circuit, and the spring 7 returns the striker to its original position.

For accurate punching, use special center punch(fig. 2.9). Kerner shown in Fig. 2.9, a, is a stand 3 with a center punch 2. The indentations of the marks before punching are lubricated with oil, the center punch with the legs 5 fixed in the stand / is installed on the intersecting risks of the part so that two legs located on one straight line fall into the same risk, and the third leg is at risk, perpendicular to the first. Then the center punch will exactly hit the point of intersection of the marks. Screw 4 prevents the center punch from turning and falling out of the body.

Another design of a punch for the same purpose is shown in Fig. 2.9, b. This center punch differs from the previous design in that the impact on the core is made with a special weight 6, which, upon impact, rests against the collar of the center punch.

As a percussion tool when performing core recesses, a metalwork hammer is used, which should have a low weight. Depending on how deep the core hole should be, hammers weighing from 50 to 200 g are used.

When performing spatial marking, it is necessary to use a number of devices that would allow you to expose the part to be marked in a certain position and tilt (turn over) it during the marking process.

For these purposes, marking plates, prisms, squares, marking boxes, marking wedges, jacks are used for spatial marking.

Marking plates(Fig. 2.10) are cast from gray iron, their working surfaces must be precisely machined. On the upper plane of large marking plates, longitudinal and transverse grooves of small depth are planed, dividing the surface of the plate into square plots... Marking plates are installed on special stands and pedestals (Fig. 2.10, a) with boxes for storing marking tools and devices. Small marking plates are placed on the tables (Figure 2.10, b).

The working surfaces of the marking board should not have significant deviations from the plane. The magnitude of these deviations depends on the dimensions of the slab and is given in the corresponding reference books.

Marking prisms(fig. 2.11) are made with one and two prismatic recesses. In terms of accuracy, prisms of normal and increased accuracy are distinguished. Normal precision prisms are made of steel grades XG and X or from carbon tool steel grade U12. The hardness of the working surfaces of the prisms must be at least HRC 56. The high-precision prisms are made of gray cast iron of the SCh15-23 grade.

When marking stepped shafts, prisms with a screw support are used (Figure 2.12) and prisms with movable cheeks, or adjustable prisms (Figure 2.13).

Squares with shelf(Figure 2.14) is used for both planar and spatial markings. In planar marking, the squares are used to make scratches parallel to one of the sides of the workpiece (if this side is pre-processed), and for making scratches in the vertical plane. In the second case, the ledge of the scribe square is installed on the scaffold plate. For spatial marking, the square is used to align the position of the parts in the marking device in the vertical plane. In this case, a marking square with a shelf is also used.

Marking boxes(Fig. 2.15) are used for installation on them when marking workpieces of complex shape. They represent a hollow parallelepiped with holes made on its surfaces for fixing blanks. With large sizes of marking boxes, in order to increase the rigidity of the structure, partitions are made in their inner cavity.

Marking wedges(Figure 2.16) is used when it is necessary to adjust the position of the workpiece to be marked in height within insignificant limits.

Jacks(Fig. 2.17) are used in the same way as adjustable wedges for adjusting and aligning the position of the workpiece to be marked in height, if the part has a sufficiently large mass. The jack support, on which the workpiece to be marked is installed, can be spherical (Figure 2.17, a) or prismatic (Figure 2.17, b).

In order for the marking marks to be clearly visible on the surface of the workpiece to be marked, this surface should be painted, i.e., covered with a compound whose color is in contrast to the color of the material of the workpiece being marked. For coloring the surfaces to be marked, special compounds are used.

Materials for painting surfaces are selected depending on the material of the workpiece, which is being marked, and on the state of the surface to be marked. To paint the surfaces to be marked, use: a solution of chalk in water with the addition of wood glue, which ensures reliable adhesion of the coloring composition to the surface of the workpiece to be marked, and a desiccant, which facilitates the rapid drying of this composition; copper sulfate, which is copper sulfate and, as a result of the ongoing chemical reactions, ensures the formation of a thin and durable layer of copper on the surface of the workpiece; quick-drying paints and enamels.

The choice of the coloring composition for application to the surface of the workpiece depends on the material of the workpiece and the state of the surface to be marked. Untreated surfaces of workpieces obtained by casting or forging are painted with dry chalk or a solution of chalk in water. Mechanically processed (preliminary filing, planing, milling, etc.), the surfaces of the workpieces are painted with a solution of copper sulfate. Copper sulfate can only be used in cases where the workpieces are made of ferrous metal, since there is no such thing as between non-ferrous metals and copper sulfate. chemical reaction with the deposition of copper on the surface of the workpiece.

Billets from copper, aluminum and titanium alloys with pretreated surfaces are painted using quick drying varnishes and paint.

The markup is done with various instruments and devices, which include a scribe, a compass, a thickness gauge, a height gauge, a scale altimeter, squares, coal-nicky-center detectors, center punch, bell, hammer, marking plate,

The scribe is used to draw lines (scribbles) on the surface to be marked with a ruler, square or template. The risk is carried out only once, then it turns out to be clean and correct, The methods of using the scribe are shown in Fig. 1.

Rice. 1. Scribe and its application: a - scribe, b - two positions of the scribe when drawing risks: correct (left) and wrong (right), c - applying risks with the curved end of the scribe

The scribe is made of U10-U12 carbon tool steel. Its ends are hardened over a length of about 20 mm. The scribe is sharpened on sharpening machine, while holding it with the left hand for the middle, and with the right hand for the non-sharpened end. Putting the tip of the scribe to the rotating stone, turn it evenly with the fingers of both hands around the longitudinal axis.

The compass serves to carry linear dimensions from the scale bar to the workpiece, dividing lines into equal parts for constructing corners, marking circles and curves, to measure the distances between two points, followed by determining the size using the scale bar.

There are simple marking compasses (Fig. 2, a) and spring (Fig. 2, b). A simple compass consists of two pivotally connected legs, solid or with plug-in needles. To fix the open legs in the required position, an arc is attached to one of them

Rice. 2. Compasses: a - simple, b - spring

In a spring compass, the legs are connected by a spring ring. Dilution and convergence of the legs is carried out by rotating in one direction or the other of the detachable nut along the set screw.

The legs of the compass are made of steel grades 45 and 50. The ends of the working parts of the legs are hardened over a length of about 20 mm.

The thickness gauge is used to draw parallel, vertical and horizontal lines, as well as to check the installation of parts on the plate. The thickness gauge consists of a cast iron base, a stand and a scribe. The scribe can be fixed anywhere on the rack, rotated around the axis and tilted at any angle. In fig. 3, b shows various types of planes and methods of using them.

Rice. 3. The thickness gauge and its application: a - general view of the thickness gauge: 1 - base, 2 - stand, 3 - scribe needle, 4 - set screw for needle insertion for precise setting of the size, 5 - thrust pins; b - some techniques for using the thicknessing gauge: 1 - parallel scoring (the thrust pins of the gauge are lowered down with springs, and the gauge rests with them against the edge of the tile to be marked), 2 and 3 - drawing marks at different positions of the gauge needle, 4 and 5 - circular scoring on disks; c - thickness gauges for marking sheet material: 1 - a sliding thickness gauge with an exact setting on the size, 2 - a plate for drawing marks from the edge of the sheet at one certain distance from it, 3 - a slotted sliding thickness gauge with setting the size according to a scale ruler

Large scale altimeter. In addition to the previously described scale ruler, used to determine linear dimensions and draw straight lines on the surface of the workpieces to be marked, a scale altimeter is used to measure distances and lay down dimensions vertically.

Marking vernier caliper is intended for drawing circles of large diameters. It consists of a bar with millimeter divisions and two legs - fixed and movable with a vernier. The legs, which are secured in the desired position with locking screws, have insertable needles that can be placed above or below, which is very convenient when circumscribing a circle at different levels.

Rice. 4. Scale altimeter (near the thickness gauge)

Rice. 5. Marking vernier caliper with inserted needles: 1 - fixed leg, 2 - bar, 3 - locking screw for fixing the frame, 4 - frame with vernier, 5 - one hundred. screw for attaching the insert needle, 6 - movable leg, 7 - insert needles

In fig. 6 shows a marking caliper of another type for more accurate marking of straight lines and centers and shows examples of its use.

A height gauge is used to check heights and more accurately apply centering and other marking lines to the treated surfaces.

Squares are used to draw vertical and horizontal lines on the surfaces to be marked, to check the correct installation of parts on the plate, as well as to mark sheet and strip material, center-detecting squares are used to apply marks passing through the center to the ends of round products. The center-finder square (fig. 30) consists of two strips connected at an angle; the working edge of the ruler passes through the middle of the corner. The connecting strip serves for the rigidity of the device. When marking the centers, the part to be marked is placed on the end. A square is applied to the upper end so that the planks connected at an angle touch the part. Risk is drawn along the ruler with a scribe. Then the part or square is turned by about 90 ° and the second risk is carried out. The intersection of the scratches defines the center of the end face of the part.

Rice. 6. Vernier caliper for accurate marking of straight lines and centers (a) and its use (b)

Rice. 7. Standing height: 1 - bar, 2 - frame clamp, 3 - frame, 4 - base, 5 - leg for measuring trots, 6 - vernier, 7 - micrometric frame feed, 8 - leg for marking

Rice. 8. Marking square and its application. a - square with a shelf, b - setting the square when drawing (or checking) vertical lines, c - position of the square when drawing lines in the horizontal plane

The center punch is used to apply small indentations at the risks. This tool is a round, knurled in the middle part of the rod, at one end of which there is a conical point with an angle of 45-60 ° at the vertex; the other end of the center punch is drawn to a cone; this end is hit with a hammer during punching.

Rice. 9. Angle center finder

Rice. 10. Kerner

Center punch is made of U7A carbon tool steel. Their working part (tip) is hardened to a length of about 20 mm, and the striking part to a length of about 15 mm.

The point of the center punch is sharpened on a grinding machine, fixing the center punch in the chuck; in no case should you hold the center punch in your hands when sharpening.

When punching, the center punch is taken with three fingers of the left hand - thumb, index and middle, as shown in Fig. 32. The point of the center punch is set exactly at the middle of the marks or at the point of intersection of the marks. Before hitting, tilt the center punch slightly away from you in order to place it more accurately, and at the moment of impact, without moving the center punch from the risks, put it vertically. The hammer blow is easy.

The hammer for striking the center punch should be lightweight, about 50-100 g.

The bell is a special device that makes it easy and convenient to mark the center and punch center holes on the ends of round parts. The device is placed on the end of the part with a tapered hole; the center punch of the bell is automatically set to the center of the end face of the part. A light blow of a hammer on the center punch marks the center.

Rice. 11. Punching: a - setting the center punch at risk, b - position of the punch when hit with a hammer, c - marked and punched out part before processing (above) and after processing (below)

Rice. 12. Bell for punching centers

Rice. 13. Spring center punch

The spring center punch has a three-piece screwed body. The body contains two springs, a rod with a center punch, a striker with an offset cracker and a flat spring. When punching, that is, when you press on the product with the tip of the punch, the inner end of the rod abuts against the cracker, as a result of which the striker moves up and compresses the spring. Leaning against the rib of the shoulder, cracker

moves to the side, and its edge comes off the rod. At this moment, the striker, under the action of the force of the compressed spring, inflicts a strong blow on the end of the rod with the center punch. Immediately after this, the spring restores the initial position of the center punch.

An electric center punch consists of a body, springs, a striker, a coil with a lacquered wire winding, a center punch. When you press the tip of the punch installed at the risk, the electrical circuit is closed and the current, passing through the coil, creates a magnetic field, the striker is instantly drawn into the coil and strikes the punch rod. During the transfer of the punch to another point, the spring opens the circuit, and the spring returns the striker to its original position.

Rice. 14. Electric center punch

Rice. 15. Marking plate on the table

The marker plate is the main tool for marking. It is a cast iron plate with a precisely machined top surface and sides. The product to be marked is installed on the plane of the plate and the marking is made. Protect the surface of the marker from damage and impact. At the end of the marking, the slab is wiped off with a dry clean cloth or washed with kerosene and oiled, then covered with a protective wooden shield.

When marking, various devices are used in the form of pads, prisms, cubes.

The main stages of marking

Before marking, the workpiece is carefully examined, checking whether it has defects - shells, bubbles, cracks, films, distortions, whether its dimensions are correct, whether the allowances are sufficient. After that, the surface planned for marking is cleaned of scale and residues of molding earth and irregularities (hillocks, burrs) are removed from it, then they proceed to staining

Coloring of the workpiece is done so that the marking lines are clearly visible during processing. Black, i.e. untreated, as well as roughly processed surfaces are painted with chalk, fast-drying paints or varnishes. Chalk (powder) is diluted in water to thicken the milk and a little linseed oil and desiccant are added to the resulting mass. It is not recommended to rub the surface to be marked with a piece of chalk, as the chalk quickly crumbles and the marking lines disappear.

Copper sulfate is used to paint cleanly treated surfaces - in solution or in pieces. A solution of copper sulfate (two to three teaspoons per glass of water) is applied to the surface with a brush or cloth; lumpy vitriol is rubbed onto surfaces moistened with water. In both cases, the surface is covered with a thin and durable copper layer, on which the marking lines are clearly visible.

Before applying markings to the painted surface, determine the base from which the risks will be applied. For planar marking, the bases can be the outer edges of flat parts, strip and sheet material, as well as various lines drawn on the surface, for example, center, middle, horizontal, vertical or oblique. If the base is the outer edge (bottom, top ^ and side), then it must first be aligned.

Risks are usually applied in the following order: first, all horizontal risks are drawn, then vertical, then oblique and, finally, circles, arcs and roundings.

Since the risks during work are easy to wipe with your hands and they will then become poorly visible, small indentations are filled with a center punch along the lines of the marks. These indentations - the cores should be shallow and divided by a line in half.

The distance between the center pins is determined by eye. On long lines of a simple outline, these distances are taken from 20 to 100 mm; on short lines, as well as in corners, bends or roundings - from 5 to 10 mm.

Marking lines do not center on the machined surfaces of precision products.

Marking by templates and by product in plumbing

A template (Fig. 1) is the simplest device used to manufacture or check homogeneous parts or products in serial and mass production. Marking templates are used to mark such parts that are repeated in production and whose shapes do not often change. The templates are made from sheet steel with a thickness of 1.5 to 4 mm.

Depending on the quantity, accuracy and size of the parts to be marked, templates can be hardened and unhardened.

Rice. 1. Templates: 1 - for marking the contour of a flat part. 2 - for marking the keyway, 3 - for marking holes

Marking circles, centers and holes in plumbing

When marking, all geometric constructions are made using two lines - a straight line and a circle (in Fig. 38, with a whole repetition, the elements of a circle are shown).

A straight line is depicted as a line drawn with a ruler. A line drawn along a ruler will be straight only if the ruler itself is correct, that is, if its edge represents a straight line. To check the correctness of the ruler, arbitrarily take two points and, attaching an edge to them, draw a line; then move the ruler on the other side of these points and draw a line again along the same edge. If the ruler is correct, then both lines will coincide, if not, the lines will not coincide.

Rice. 1. Circle and its elements

Circle. Finding the center of the circle. On flat parts, where there are already ready-made holes, the center of which is unknown, the center is found geometrically. At the ends of the cylindrical parts, the center is found using a compass, a planer, a square, a center finder, a bell (Fig. 2).

The geometric method for finding the center is as follows (Fig. 2, a). Suppose you are given a flat metal plate with a finished hole, the center of which is unknown. Before starting the marking, a wide wooden block is inserted into the hole and a metal plate made of tinplate is stuffed onto it. Then, at the edge of the hole, three points L, B and C are lightly marked arbitrarily, and from each pair of these points AB and BC they describe arcs until they intersect at points 1, 2, 3,4; draw two straight lines towards the center until they intersect at point O. The intersection point of these straight lines will be the desired center of the hole.

Rice. 2. Finding the center of the circle: a - geometrically, b - marking the center with a compass, c - marking the center with a thickness gauge, d - marking the centers in a square, e - punching with a bell

Marking the center with a compass (Fig. 2, b). Clamping the part in a vice, spread the legs of the compass slightly more or less than the radius of the part being marked. After that, attaching one leg of the compass to the side surface of the part and holding it with your thumb, draw an arc with the other leg of the compass. Next, move the compass on a circle (by eye) and in the same way outline the second arc; then, through each quarter of the circle, outline the third and fourth arcs., The center of the circle will be inside the outlined arcs; it is stuffed with a center punch (by eye). This method is used when great accuracy is not required.

Marking the center with a thickness gauge. The part is placed on prisms or parallel shims placed on a screed plate. The sharp end of the planer needle is installed slightly above or below the center of the part to be marked and, holding the part with the left hand, move the planer along the plate with the right hand, tracing it with a needle at the end of the part with a short risk. After that, the part is turned by! D circle and the second risk is carried out in the same way. The same is repeated every quarter of a turn for the third and fourth lines. The center will be inside the marks; it is stuffed in the middle with a center punch (by eye).

Marking the center in a square. A square-center-finder is applied to the end of the cylindrical part. Pressing it with your left hand to the part, with your right hand draw along the line of the center finder using a scribe at risk. After that, the part is turned approximately ‘/’ of the circle and the second risk is drawn with a scraper. The point of intersection of the marks will be the center of the end, which is stuffed with a center punch.

Rice. 3. Division of a circle into parts

Marking the center with a bell (Fig. 2, e). The bell is installed on the end of the cylindrical part. Holding the bell with the left hand in an upright position, with the right hand strike with a hammer on the center punch in the bell. The center punch will make a recess in the center of the butt end.

Division of a circle into equal parts. When marking circles, you often have to divide them into several equal parts - 3, 4, 5, 6 and more. Below are examples of dividing a circle into equal parts geometrically and using a table.

Division of a circle into three equal parts. First, the diameter AB is carried out. From point A, the radius of a given circle is described by arcs that mark points C and D on the circle. Points B, C and D obtained from this construction will be points dividing the circle into three equal parts.

Division of a circle into four equal parts. For such a division, two mutually perpendicular diameters are drawn through the center of the Circle.

Division of a circle into five equal parts. On this circle, two mutually perpendicular diameters are drawn, intersecting the circle at points A and B, C and D. The radius OA is halved, and from the obtained point B, an arc is described with a radius of BC until it intersects at point F on the radius OB. After that, the straight lines are connected to points D and F. Putting the length of the straight line DF along the circumference, divide it into five equal parts.

Division of a circle into six equal parts. Draw the diameter intersecting the circle at points A and B. The radius of this circle is described from points A and B four arcs until they intersect with the circle. The points A, C, D, B, E, F obtained by this construction divide the circle into six equal parts.

Division of a circle into equal parts using a table. The table has two columns. The numbers in the first column show how many equal parts a given circle should be divided into. In the second column, the numbers are given by which the radius of the given circle is multiplied. As a result of multiplying the number taken from the second column by the radius of the marked circle, the chord value is obtained, that is, the distance along a straight line between the divisions of the circle.

Putting the obtained distance on the marked circle with a compass, we divide it into 13 equal parts.

Hole marking on parts. The marking of bolt and stud holes in flat parts, rings and flanges for pipes and machine cylinders requires special attention. The centers of the holes of the bolts and studs must be precisely located (marked) around the circumference so that when two mating parts are superimposed, the corresponding holes are exactly one below the other.

After the marked circle is divided into parts and the centers of the holes are punched in the proper places along this circle, they begin to mark the holes. When punching the centers, first, the recess is punched only slightly and then check the equality of the distance between the centers with a compass. Only after making sure of the correctness of the markup, the centers are finally nailed.

The holes are marked with two circles from one center. The first circle is drawn with a radius according to the size of the hole, and the second, as a control, with a radius of 1.5-2 mm larger than the first. This is necessary so that during drilling it is possible to see whether the center has shifted and whether drilling is proceeding correctly. The first circle is punctured: 4 cores are made for small holes, 6-8 and more for large holes.

Rice. 5. Hole markings: 1 - a marking ring, 2 - a wooden plank hammered into a hole, 3 - drawing a circle, 4 - marking holes, 5 - marked holes, 6 - a circle of the centers of holes, 7 - a control circle, 8 - cores

Marking corners and slopes in plumbing

When marking, you have to build different angles, more often 90, 45, 60, 120, 135, 30 °.

To measure angles, special tools are used - a protractor and a protractor.

The protractor has the shape of a semicircle, divided into 180 equal parts. The center of the semicircle is indicated by a small notch O. When measuring the angle with a protractor, it is applied to the angle so that the apex of the angle coincides with the Center of the protractor and one of the sides of the corner - with the base line of the inner semicircle. Then, on the scale of the protractor, the degrees enclosed between it and the second side of the angle are counted from this side of the angle. Protractor (Fig. 43) consists of two disks sitting on the same axis. The disc with graduations in degrees marked on it is one piece with a fixed ruler. The second - a rotary disk with a vernier attached to it is connected to a movable ruler, which can be set to the required length and fixed by means of a screw. When the disc is rotated, the ruler rotates and, as a result, full contact of the edges of both rulers with the sides of the measured angle is achieved. After that, both rulers are fixed with a screw. When measuring, whole degrees are counted along the disk, starting from zero to the right or left, to zero division of the vernier; minutes are counted on the vernier also from zero - until the division of the vernier coincides with the division on the disk. The measurement accuracy with a universal goniometer can be brought up to 5 minutes.

Rice. 1. Universal goniometer and its application: a - goniometer device: 1 - disk, 2 - rotary disk, 3 - hinge screw, 4 - movable ruler, 5 - fixed line of protractor; b - measurements with a protractor

Rice. 2. Construction of perpendicular lines: o -line intersecting line AB in the middle, b - perpendicular to line AB at point C on the straight line, a - perpendicular to line AB from point C, which is not on this line, d - perpendicular at the end of line AB

The marking of corners is reduced to the construction of perpendicular and oblique lines on the parts. In order to repeat by students these already familiar constructions in fig. 1 gives examples for building exercises.

Marks parallel lines from the edge of the material and from the center lines

The marking of parallel lines on the surface of parts can be performed both geometrically and using marking tools - a scale ruler, a square and a scribe, a compass and a planer.

Let's consider the markup with instruments using three examples.

Rice. 1. Construction of inclined lines and slopes: a - straight lines dividing any angle in half, b - straight lines dividing a right angle into three equal parts, c - with obtaining the slope size in the form of a fraction, d - as a percentage

1. Let's take the end and side sides of the strip as a marking base
2. Paint the surface to be marked with diluted chalk.
3. Measure the length of the cut piece of metal on the strip. To do this, put a scale ruler on the surface to be marked so that the 100 mm ruler division coincides with the edge of the strip end. Then, without moving the ruler, we make a mark at its beginning with a scribe.
4. To draw a cutting line on the strip, place a square on it so that one side of it is firmly pressed against the side of the strip, and the other exactly coincides with the mark. On this side of the square, without moving it from its place, we draw a transverse risk with a scribe.
5. After that, to make the cut point more noticeable, on the drawn risk we fill the cores at a distance of 8 mm from each other.

Rice. 2. Geometric method of constructing parallel lines: a - along a straight line and a point outside it, b - at a certain distance from each other, c - along a given straight line, arbitrarily

Rice. 3. Marking lines from the edge of the part: a - scribing marks along the scale ruler, b - drawing a line in a square

Rice. 4. Marking of parallel lines: a - marking, b - drawing marks in a square, c - marked part

Rice. 5. Marking with a compass: a - setting the legs of the compass to the size on the scale, b - transferring the dimensions to the part by drawing marks with a compass

Example 2.
Mark parallel straight lines 10 mm apart on the machined surface of the steel part using a scale ruler, scribe and square.
1. We take the bottom and side sides of the part as the marking base.
2. We paint the surface of the part to be marked with a solution of copper sulfate.
3 We put a scale ruler on the part so that its beginning or any selected division exactly coincides with the edge of the part; firmly pressing the ruler with your left hand to the surface to be marked, we make marks on it with a scribe every 10 mm.
4. Through the applied marks but on the square superimposed on the part, draw parallel risks with a scraper.

Example 3. On a machined brass strip, mark four points in the corners with a compass for the centers of the holes at a distance of 20 mm from the ribs of the strip.
1. We take the sides of the plank as the marking base.
2. We do not paint the surface, since the drawn marks are very clearly visible on non-ferrous metal and without painting.
3. Using a compass on a scale ruler, remove the size of 20 mm.
4. Without knocking down the compass, draw two intersecting lines from the ribs of the plank.
5. At the points of intersection of the lines, we core depressions for the centers of the holes.

Marking of unfolded cube, cylinder and cone

It is often necessary to resort to the construction of sweeps of a cube, cylinder and cone in the manufacture of products from sheet material.

Rice. 1. Cube sweep (a) and cylinder sweep (b)

Unfolded cube (Fig. 1, a).

The cube is limited by six square planes, equal in size to each other. Each plane is called a face. The faces are mutually perpendicular, that is, they are located at right angles to each other. The straight line along which two faces intersect is called the edge of the cube; there are 12 ribs in a cube. The point where the three edges of the cube converge is called the vertex; there are 8 vertices in a cube. To connect the faces, a seam allowance is added to the flat pattern.

Cylinder sweep. The expanded cylinder (Fig, 1, b) is a rectangle with a height equal to the height H of the cylinder and a length equal to the circumference of the base of the cylinder. To determine the circumference of a cylinder, you need to multiply the diameter of the base of the cylinder by 3.14, that is, L - lb.

To get a full scan (on sheet material), you must add an allowance for the bend connection (seam connection) and for the flange for wire seaming to the unfolded dimensions.

Rice. 2. Development of the cone

Development of the cone (Fig. 2, a). The unfolded surface of the cone looks like a sector. Graphical construction of a flat pattern of a cone can be performed in two ways.

The first way. Point O is marked and from it, as from the center, a part of a circle is described with a radius equal to the length of the generatrix of the cone.

Second way. Draw the profile of the cone and from its vertex O with a radius equal to the length of the generatrix, describe part of the circle - arc A. Then divide the diameter of the base of the cone into seven equal parts and postpone the resulting segment along arc A from point 1 22 times. Connecting the last point 2 with the center O, we get a sweep of the cone. If a seam connection or wire rolling is envisaged, an allowance is given.

A truncated cone is constructed in the same way (Fig. 2, b).

Rejection in plane marking, precautions and rules for safe work

There are times when the parts processed according to the marking turn out to be a marriage. This type of marriage can arise both for reasons beyond the control of the striper, and through his fault. Reasons that do not depend on the scribe are work on incorrect drawings, marking on the wrong scribe and inaccurate devices - prisms, cubes, pads, the use of inaccurate or worn-out measuring and control tools (if these shortcomings of the tool were not known to the scribe).

Dimension error. Such an error is the result of an inattentive reading of the drawing by a scribe who does not understand the dimensions indicated on the drawing. The scribe, if he himself is not able to understand the drawing, is obliged to seek clarification from the master.

Inaccuracy in setting the dimensions on the scale bar. Here the fault may be either the carelessness of the marketer, or the lack of sufficient skills in using marking and measuring tools.

Incorrect postponing of dimensions, that is, using as bases of the wrong surfaces from which the markup should have been carried out. In such cases, roughness often remains on the surfaces of the part after its processing, that is, places that the processing has not touched, and the part goes to waste. The marketer must remember that the marking is carried out not from randomly taken surfaces, but from pre-marked base surfaces to the lines.

Careless installation of the part on the marker plate, i.e. inaccurate alignment with new installations. The displacement of the part in the process of marking inevitably gives distortions; the part marked in this position is rejected after processing.

All these markup errors are due to the marker's carelessness. The main condition for high-quality marking is a conscientious, attentive attitude of the marketer to his work. The scribe is obliged to use only serviceable and accurate tools, completely suitable devices. After the end of the marking, it is necessary to carefully check the correctness of the work performed.

General concepts about felling in plumbing

Cutting is the processing of metal with a cutting and percussion tool, as a result of which excess metal layers are removed (cut down, cut down) or metal is cut into pieces for further processing and use. As a cutting tool in plumbing, a chisel or craidmeisel is usually used, and as a percussion tool, simple or pneumatic hammers.

With the help of the felling you can produce:
- removal (cutting) of excess metal layers from the surfaces of the workpieces;
- leveling uneven and rough surfaces;
- removal of hard crust and scale;
- chopping off edges and burrs on forged and cast blanks;
- chopping off after assembly of the protruding edges of the sheet material, the ends of the strips and corners;
- cutting into pieces of sheet and high-quality material;
- cutting holes in sheet material along the outlined contours;
- cutting edges into a butt for welding;
- cutting off the heads of the rivets when they are removed;
- cutting out lubricating grooves and keyways.

Cutting is done in a vice, on a slab or on an anvil; bulky parts can be handled by felling at their location. A chair vise is best suited for chopping; It is not recommended to cut on a parallel vise, since their main parts - jaws made of gray cast iron, often do not withstand strong impacts and break.

The part to be cut by the felling must be motionless. Therefore, small parts are clamped in a vice, and large parts are placed on a workbench, stove or anvil, or they are placed on the floor and well strengthened. Regardless of where the felling is carried out, the installation of parts in height should be made in accordance with the height of the worker.

When starting a felling, a locksmith first of all prepares his workplace. Taking a chisel and a hammer from a workbench box, he puts the chisel on the workbench on the left side of the vise with the cutting edge facing him, and the hammer on the right side of the vise with a striker directed towards the vise.

When cutting, one must stand at the vise straight and stable, so that the body is to the left of the vise axis.

Rice. 1. Reception of felling: a - elbow swing, b - shoulder swing, c - the correct position of the legs of the worker when cutting, d - holding the chisel

The left leg is put forward half a step, and the right leg, which serves as the main support, is slightly set back, spreading the feet at an angle approximately as shown in Fig. 1, c.

Hold the chisel in your hands as shown in fig. 1, d, loosely, without excessive clamping. During cutting, they look at the working part of the chisel, more precisely, at the cutting place, and not at the striking part, which is hit with a hammer. It is only necessary to chop with a sharply sharpened chisel; a blunt chisel slides off the surface to be chopped off, the hand quickly gets tired of this, as a result, the correctness of the blow is lost.

The depth and width of the metal layer (shavings) removed by the chisel depend on the physical strength of the worker, the size of the chisel, the weight of the hammer and the hardness of the metal being processed. The hammer is selected by weight, the size of the chisel - along the length of its cutting edge. For every millimeter of chisel length, 40 g of hammer weight is required. Hammers weighing 600 g are usually used for cutting.

Depending on the order of operations, felling can be rough and final. During rough cutting, a layer of metal with a thickness of 1.5 to 2 mm is removed in one pass with strong hammer blows. During final felling, a layer of metal with a thickness of 0.5 to 1.0 mm is removed per pass, inflicting lighter blows.

To obtain a clean and smooth surface, it is recommended to wet the chisel with machine oil or soapy water when cutting steel and copper; cast iron should be cut without lubrication. Brittle metals (cast iron, bronze) must be cut from edge to middle. In all cases, when approaching the edge of the part, you should not finish cutting the surface to the end, it is necessary to leave 15-20 mm to continue cutting from the opposite side. This prevents chipping and chipping of corners and edges of the workpiece. At the end of cutting metal, as a rule, it is necessary to weaken the blow with a hammer on a chisel.

Cutting in a vice is carried out either at the level of the jaws of the vice, or above this level - according to the intended risks. According to the level of the vice, thin strip or sheet metal is most often cut, above the level of the vice (in terms of risks), the wide surfaces of the workpieces.

When chopping off wide surfaces, a cross cutter and a chisel should be used to speed up the work. First, the grooves of the required depth are cut with a cross cutter, and the distance between them should be equal to 1D of the length of the chisel cutting edge. The formed protrusions are cut off with a chisel.

To cut correctly, you need to have a good command of the chisel and hammer: this means holding the chisel and hammer correctly, moving the hand, elbow and shoulder correctly, and hitting the chisel with a hammer accurately, without a miss.

division of metal shavings, which is the essence of the cutting process.

The tool used for cutting - the chisel - is the simplest cutting tool, in which the wedge is especially pronounced. The wedge as the basis of any cutting tool must be strong and regular in shape - have front and back edges, a cutting edge and an angle of sharpness.

The front and back faces of a wedge are two generating planes that intersect at a certain angle. The edge that faces outward during operation and along which the chips come off is called the front; the edge facing the workpiece is the back.

The cutting edge is the sharp edge of the tool formed by the intersection of the leading and trailing edges. The surface that is formed on the workpiece directly by the cutting edge of the tool is called the cutting surface.

Normal cutting conditions are ensured by the cutter's rake and clearance angles.

In fig. 2 shows the angles of the cutting tool.

The rake angle is the angle between the leading edge of the wedge and the plane perpendicular to the cutting surface; denoted by the letter g (gamma).

Clearance angle - the angle formed by the back face of the wedge and the cutting surface; denoted by the letter a (alpha).

Taper angle - the angle between the front and back edges of the wedge; denoted by the letter p (beta). the division of the metal layer from the rest of its mass is as follows. The wedge-shaped steel body of the cutting tool, under the action of a certain force, presses on the metal and, compressing it, first displaces and then cleaves the metal particles. Previously broken off particles are displaced by new ones and move up the front edge of the wedge, forming shavings.

Rice. 2. Cutting patterns and cutting angles

Chipping of chip particles occurs along the shear plane MN, located at an angle to the front edge of the wedge. The angle between the plane of the cleavage and the direction of movement of the tool is called the cleavage angle.

Consider the action of a wedge when a simple planing cutter is working (Fig. 3). Suppose you want to remove a certain layer of metal from workpiece A with a cutter. To do this, a cutter is installed on the machine so that it cuts the metal to a given depth, and the action of a certain force P imparts continuous movement to it in the direction indicated by the arrow.

A cutter made of a rectangular bar, devoid of wedge corners, does not separate the chips from the metal. It crumples and presses the removed layer, tears and bangs the treated surface. It is clear that such a tool cannot be used.

In fig. 54 shows a cutter with a wedge-shaped working part. The cutter easily separates the chips from the rest of the metal mass, and the chips freely flow down the cutter, leaving a smooth machined surface.

Chisel. The chisel is an impact cutting tool used in metal cutting. In fig. 55, and a drawing of a chisel is given. The end of the working part of the chisel has a wedge-shaped shape, which is created by sharpening two symmetrical surfaces at a certain angle. These surfaces of the working part are called the chisel edges. The edges at the intersection form a sharp edge called the chisel cutting edge.

The edge along which the chips come off during cutting is called the front, and the edge facing the work surface is called the back. The angle a formed by the edges of the chisel is called the taper angle. The angle of sharpening of the chisel is selected depending on the hardness of the metal being processed. For hard and brittle metals, the angle a should be greater than for soft and ductile metals: for cast iron and bronze, the angle a is taken 70 °, for steel - 60 °, copper and brass - 45 °, aluminum and zinc - 35 °, medium shape part of the chisel is such that it allows you to comfortably and firmly hold it in your hand during felling. The sides of the chisel should have rounded and cleaned edges.

Rice. 3. Cutter in the process of cutting: L - product, 1 - cutter, 2 - depth of the removed layer, P - force acting during cutting

The striking part of the chisel has the form of a truncated cone of irregular shape with a semicircular upper base. With this shape of the striking part, the force of the hammer striking the chisel is used with the best result, since the strike always hits the center of the striking part.

Rice. 4. Chisel (a) and crosscutter (b) Chisel dimensions in mm

When cutting metal, the chisel is held in the left hand by the middle part, freely grasping it with all fingers so that the thumb rests on the index finger (Fig. 56) or on the middle one if the index finger is in an extended position. The distance from the hand to the striking part of the chisel must be at least 25 mm.

Rice. 5. Position of the chisel when cutting: a - cutting at the level of the vice, 6 - cutting at risk

Rice. 6. Installation of the chisel on the workpiece but in relation to the vise jaws

For cutting, the chisel is installed on the workpiece, as a rule, with the inclination of the rear edge to the work surface at an angle, but not more than 5 °. With such an inclination of the back face, the angle of inclination of the chisel (its axis) will be made up of the sum of the back angle and half of the taper angle. For example, with a 70 ° taper angle, the tilt angle will be 5 + 35 °, i.e. 40 °. In relation to the line of the jaws of the vise, the chisel is set at an angle of 45 °.

Correct installation of the chisel contributes to the complete transformation of the force of the hammer blow into cutting work with the least fatigue of the worker. In practice, the tilt angle of the chisel is not measured, but the correct tilt is felt by the worker, especially with the proper skill. If the angle of inclination is too large, the chisel cuts deeply into the metal and moves slowly forward; if the angle of inclination is small, the chisel tends to break out of the metal, slide off its surface.

The inclination of the chisel to the work surface and relative to the vise jaws is guided by the movement of the left hand during cutting.

Kreutzmeisel. A cross cutter is essentially a chisel with a narrow blade. It is used for cutting narrow grooves and keyways. The sharpening angles of the cross cutter are the same as those of the chisel. Sometimes a cross cutter is used instead of a chisel, for example, when the chisel is large in width of the cutting edge or when it is inconvenient to use it due to the working conditions.

Rice. 7. Sharpening of a chisel (cross-cutter) on a sharpening machine and a template for checking the correctness of sharpening

For cutting semicircular, sharp and other grooves, special shaped crosscutters are used, called grooves.

Chisel and cross-cutter sharpening. During the operation of the chisel and the cross cutter, their edges are abraded, the cutting edge is slightly fractured and the tip of the tapering angle is rounded. The cutting edge loses its sharpness, and further work with the tool becomes ineffective, and sometimes impossible. The performance of a blunt tool is restored by sharpening.

The chisel is sharpened on a grinding wheel - on a sharpening machine. Taking the chisel in hand, as shown in fig. 7, put it on a rotating circle and, with light pressure, slowly move it to the left and right over the entire width of the circle. During sharpening, the chisel is turned with one or the other face, alternately sharpening them. It is impossible to press hard with a chisel on the wheel, as this can lead to severe overheating of the tool and the loss of its original hardness by the working part.

At the end of sharpening, remove the burrs from the cutting edge of the chisel, carefully and alternately applying the edges to the rotating grinding wheel. After sharpening, the cutting edge of the chisel is tucked in on an abrasive bar.

The chisel can be sharpened with coolant / s and on a dry wheel. In this case, it is necessary to cool the chisel being sharpened by tearing it off the circle and lowering it into the water.

When sharpening a chisel, you need to carefully monitor that the cutting edge is straight, and the edges are flat, with the same angles of inclination; the taper angle should correspond to the hardness of the metal being processed. The sharpening angle is checked with a template.

The crosscutter is sharpened in the same way as the chisel.

Locksmith hammers. Earlier it was already indicated that two types of hammers are used in plumbing - with round and square strikers. The end of the hammer opposite the striker is called the toe. The toe is wedge-shaped and rounded at the end. It is used for riveting, straightening and pulling metal. During felling, a chisel or cross-meisel is struck only with the striker of a hammer.

Hammer holding methods. The hammer is held by the handle in the right hand at a distance of 15-30 mm from the end of the handle. The latter is grasped with four fingers and pressed to the palm; the thumb is placed on the index finger, all fingers are firmly squeezed. They remain in this position both when swinging and when hitting. This method is called "holding the hammer without unclenching your fingers" (Fig. 9, a).

Rice. 8. Locksmith hammers: a - with a round striker, b - with a square striker, c - jammed hammer on the handle

There is another method that involves two steps. With this method, at the beginning of the swing, when the hand moves up, the handle of the hammer is wrapped around all fingers. Later, as the hand is raised up, the clenched little fingers, the ring and middle fingers gradually unclench and support the hammer bent backward (Fig. 9, b). Then the hammer is given a push. To do this, first squeeze the unclenched fingers, then accelerate the movement of the entire arm and hand. The result is a strong hammer blow.

Rice. 9. Methods of holding the hammer when cutting: a - without unclenching the fingers, b - with unclenching the fingers

Hammer blows. When chopping, hammer blows can be performed with a wrist, elbow or shoulder swing.

The wrist swing is carried out by the movement of only the hand.

The elbow swing is performed by the elbow movement of the hand - bending it and then quickly extending it. With an elbow swing, the fingers of the hand act, which expand and contract, the hand (moving it up and then down) and the forearm. To get a strong blow, the extension movement of the arms must be done quickly enough. Exercises in the elbow swing well develop the elbow joint along with the hand and fingers.

Shoulder swing is a complete swing with the entire arm involving the shoulder, forearm, and hand.

The use of this or that swing is determined by the nature of the work. The thicker the layers of metal are removed from the treated surface, the greater the need to increase the impact force, therefore, to increase the swing; however, incorrect use of a wide swing can ruin the workpiece and the tool and quickly get tired without the need. You need to learn how to accurately measure the force of the blow according to the nature of the work performed.

A blow with a hammer on a chisel should be made with an elbow swing with fingers unclenched; with such a blow, you can chop for quite a long time without getting tired. The blows must be measured, accurate and strong.

The cutting performance depends on the hammer impact force on the chisel and the number of blows per minute. When cutting in a vice, they make from 30 to 60 beats per minute.

The force of the blow is determined by the weight of the hammer (the heavier the hammer, the stronger the blow), the length of the hammer handle (the longer the handle, the stronger the blow), the length of the worker's arm and the size of the hammer swing (the longer the arm and the higher the swing, the stronger the blow).

When chopping, it is necessary to act in concert with both hands. With your right hand, you need to accurately and accurately hit the chisel with a hammer, with your left hand, in the intervals between blows, move the chisel over the metal

Felling in a vice

In a vice, they cut sheet and strip materials, as well as wide surfaces.

Cutting of sheet material is carried out only at the level of the vise jaws. In fig. 1, a, b shows a steel plate with a wedge contour marked on it. Consider how to cut a wedge in a vice.

For this work you need a vice, a chisel, a hammer.

Rice. 1. Drawing of the part (a) and marked workpiece (b).

Way of doing work:
1) prepare a workplace - take a chisel and a hammer from a box and place them on a workbench;
2) clamp the plate in a vise so that the risk of the wedge contour is at the level of the vise jaws;
3) pick up a chisel and a hammer, stand in a vice and take a working position for cutting; set the chisel at an angle of 35 ° to the surface of the vise jaws and at an angle of 45 ° to the workpiece so that the chisel touches the metal in the middle of the cutting edge; striking a chisel with a hammer, chop off excess metal at a risk; at the end of the felling it is necessary to weaken the blows;
4) after finishing cutting, put the tool on the workbench;
5) unclench the vice, rearrange the plate with the opposite line (opposite side) upwards and re-clamp it so that the risk is at the level of the vice jaws;
6) cut off the excess metal at the risk from this side;

Rice. 2. Cutting of sheet material

Cutting of strip material. Parts made of strip material are cut in a vise at the level of the jaws or at the risks located above the vise. A layer of metal up to 1.5 mm thick is chopped off in one pass, 3 mm thick - in two passes. Thicker layers are chopped off using a cross-cutter, which is pre-cut through narrow grooves; the formed protrusions are cut off with a chisel (Fig. 3).

Cutting of wide surfaces. When cutting wide surfaces, the metal layer is cut in two stages, first, the grooves are cut with a cross-cutter, then the projections are cut off with a chisel. When cutting with the use of a crosscutter, a bevel is preliminarily cut with a chisel on the edge of the workpiece. Then, on the upper surface and on the bevel, the distances between the grooves are marked (each gap should be equal to approximately 3D the length of the cutting edge of the chisel) and marks are drawn along the bevel to mark the depth of each pass.

Rice. 4. Cutting of wide surfaces: a - cutting of grooves with a cross-cutter, b - cutting of protrusions with a chisel

After that, the marked workpiece is clamped in a vice 4-8 mm above the level of the jaws and the cutting is started.

The thickness of the c-cut for each pass of the crosscutter is from 0.5 to 1 mm, and when cutting off the protrusions with a chisel from 1 to 2 mm. When cutting with both a cross cutter and a chisel, a layer of metal of 0.5-1 mm is left for finishing with a chisel. If, after cutting, the surface must still be filed with a file, then during the final felling, leave an allowance of 0.5 mm for sawing.

Rice. 3. Cutting of strip material a - cutting of grooves with a cross-cutter in a thick steel strip, b - cutting off protrusions with a chisel

In fig. 4 shows a steel slab from which the top wide surface is to be chopped off so that it is parallel to the bottom surface.

For this work, you need a vice, a marking plate, a thickness gauge, a scale ruler, a center punch, a chisel, a hammer, and chalk.

Method of execution:
1) prepare a workplace - take a chisel, a hammer, a scale ruler, a center punch and chalk from a workbench; get a thickness gauge in the tool pantry;
2) place the entire tool on the workbench as previously indicated;
3) apply with a thickness gauge on the sides of the tile the risks, marking the thickness of the cut layer, bevel the risks;
4) clamp the tile in a vice so that the risks are higher than the jaws by 4-8 mm;
5) pick up a chisel and a hammer and stand in front of the vice in a working position;
6) cut a bevel on the front edge of the tile with a chisel for easy installation of the cross-cutter and chisel at the beginning of felling, put the chisel on the workbench;
7) take a cross cutter and cut the first groove from the right edge along the markings, removing approximately 1 mm of chips with each pass; leave a layer of metal about 0.5 mm (minimum) for fine cutting;
8) cut through the remaining grooves in the same way;
9) put a cross cutter on the workbench and take a chisel;
10) cut off the first protrusion on the right side of the tile with a chisel, removing 1 mm thick chips for each chisel pass; leave a layer of metal about 0.5 mm for finishing;
11) cut off all other projections of the tile in the same way;
12) make a final chipping (leveling) with a chisel of the entire surface of the tile, removing chips with a thickness of 0.5 mm;
13) check the straightness of the chopped off tile surface with a straight edge.

Cutting through curved grooves with a cross-cutter or a grooving tool (Fig. 5). Mark the direction of the grooves on the surface to be treated, then clamp the part in a vice with the marked surface upwards and proceed to cutting. First, a cross-cutter or a groove cutter, applying light blows with a hammer, mark the groove trace along the risks inflicted. After that, grooves are cut from one pass with a depth of 1.5-2 mm. By fine cutting, the irregularities formed in the grooves are leveled and given the same width and depth throughout.

Rice. 5. Cutting through curved grooves: 1 - on a flat surface, b-on a curved surface (in the bearing shell)

Cutting grooves and slots (longitudinal or transverse) in gas or other pipes. This work (Fig. 6) is carried out with a special cross-cutter having four cutting edges, and from the front cutting side - a surface concave along an arc.

Before proceeding with the felling, at the beginning to the end of the groove to be cut, holes are drilled with a diameter equal to the width of the groove.

The tube being processed is clamped in a vice in special nipples.

Cutting through cast iron pipes (Fig. 7). There are cases when you need to shorten a cast-iron pipe or cut off a piece from it for some need. This work is done with a cross cutter or chisel. First, a cutting line is marked along the circumference of the pipe, then the pipe is laid on wooden linings or sandbags and proceeds to cutting. It is impossible to cut the pipe by weight, since then longitudinal cracks may appear in the felling areas. During operation, the pipe must be gradually rotated around its axis and the chisel must be moved along the risk. After several full turns of the pipe, the notched part is easily detached.

Rice. 6. Cutting grooves and slots in the pipe with a special cross-cutter: 1 - cross-cutter, 2 - pipe (in section) with a cut-in cross-cutter, 3 - shavings

To cut large-diameter cast-iron pipes, a cut line is marked along their circumference and holes are drilled on it at equal distances from one another. Wooden wedges are driven tightly into the holes. After that, the gaps between the holes are cut with a chisel or cross-cutter along the risk along the entire cutting line, gradually turning the pipe around its axis. This is how the notching is continued with a turn of the pipe until the cut off part is separated from the pipe.

Rice. 7. Cutting of cast iron pipes

Similar information.

In order to increase labor productivity, innovative locksmiths use improved marking techniques and special devices.

Template markup It is usually used in the manufacture of large batches of parts of the same shape and size, but sometimes even small batches of complex products are marked out in this way.

Figure 3.3.4.1 Marking by template (B. S Pokrovsky V. A. Skakun "Locksmith" Moscow 2003)

Templates are made from sheet material with a thickness. 0.5 ... 1 mm, and for parts of complex shape or with holes - 3 ... 5 mm thick. When marking, the template is placed on a painted workpiece (part) and carried out with a scraper along the contour of the template, after which the risk is numbered, Using the templates it is convenient to mark holes for drilling, since this eliminates the need for geometric constructions - dividing segments and circles into parts, etc. ...

The holes are marked according to the template with a scribe or center punch.

Sometimes the template serves as a jig, along which the part is processed without marking. To do this, it is applied to the workpiece, then holes are drilled and the side surfaces are processed.

The expediency of using the template is that the marking work, which takes a lot of time, is performed only once during the manufacture of the template. All subsequent markup operations are only copying the outline of the template.

Layout templates can also be used to inspect a part after processing.

Sample markup differs in that it does not require the manufacture of a template. This method is widely used in repair work, when the dimensions are removed directly from the failed part and transferred to the marked material. This takes into account wear.

In-place markup more often used when assembling large parts. One part is marked on the other in such a position in which they should be connected.

Pencil markup It is produced according to a ruler on blanks made of aluminum and duralumin. Marking the latter with the help of: a scribe is not allowed, since when drawing marks, the protective layer is destroyed and conditions are created for the appearance of corrosion.

Precise markings perform according to the same rules as; usual, but more accurate measuring and marking tools are used. The surfaces of the workpieces to be marked are thoroughly cleaned and covered with a thin layer of copper sulfate solution. It is not recommended to use chalk for painting, as it is quickly erased, sticks to hands and contaminates the instrument.

When drawing marks, use a height gauge with an accuracy of 0.05 mm, and the installation and alignment of the workpieces is carried out according to the indicator. A more accurate installation can be performed using plane-parallel measures of length (tiles) and fixing them in special holders. The risks are shallow, and the punching is done with a sharpened center punch with three legs located at an angle of 90 ° to each other.

The markings must exactly correspond to the dimensions indicated in the drawing; marking risks should be clearly visible, not be erased during the processing of the workpiece, not worsen the appearance and not reduce the quality of the part, i.e. the depth of the marks and core holes must meet the technical requirements.

Markup- the operation of applying marking lines (marks) to the workpiece to be processed, which determine the contours of the future part or the places to be processed. The marking accuracy can reach 0.05 mm. Before marking, it is necessary to study the drawing of the part being marked, find out the features and dimensions of the part, its purpose. The markup must meet the following basic requirements: exactly match the dimensions indicated on the drawing; the marking lines (risks) must be clearly visible and not be erased during the processing of the workpiece. To install the parts to be marked, marking plates, pads, jacks and swivel devices are used. For marking, scribes, center pins, marking calipers and planes are used. Depending on the shape of the blanks and parts to be marked, planar or spatial (volumetric) markings are used.

Plane marking are performed on the surfaces of flat parts, as well as on strip and sheet material. When marking, contour lines (risks) are applied to the workpiece according to specified dimensions or according to templates.

Spatial markup the most common in mechanical engineering and differs significantly from the plane. The difficulty of spatial marking is that it is necessary not only to mark the surfaces of the part located in different planes and at different angles to each other, but also to link the marking of these surfaces to each other.

Base- the reference surface or baseline, from which all dimensions are measured when marking out. It is chosen according to the following rules: if the workpiece has at least one processed surface, it is chosen as the base; in the absence of processed surfaces at the workpiece, the outer surface is taken as the base.

Preparation of blanks for marking begins with cleaning it with a brush from dirt, scale, and traces of corrosion. Then the workpiece is cleaned with sanding paper and degreased with white spirit. Before painting the surface to be marked, you must make sure that there are no cavities, cracks, burrs and other defects on the part. The following compositions are used to paint the surfaces of the workpiece before marking: chalk diluted in water; ordinary dry chalk. Rubbed with dry chalk the unprocessed surfaces of small irresponsible workpieces, since this color is fragile; copper sulfate solution; alcohol varnish is used only for accurate marking of the surfaces of small products. The choice of the coloring composition for application to the base surface depends on the type of workpiece material and the method of its production: untreated surfaces of workpieces made of ferrous and non-ferrous metals obtained by forging, stamping or rolling are painted with an aqueous solution of chalk; the treated surfaces of workpieces made of ferrous metals are painted with a solution of copper sulfate, which, when interacting with the workpiece material, forms a thin film of pure copper on its surface and provides a clear selection of marking marks; the processed surfaces of workpieces made of non-ferrous metals are painted with quick-drying varnishes.

Markup methods

Pattern marking is used in the manufacture of large batches of parts of the same shape and size, sometimes for marking small batches of complex workpieces. Marking by a sample is used for repair work, when the dimensions are taken directly from the failed part and transferred to the marked material. This takes into account wear. A sample differs from a template in that it has a one-time use. Marking in place is made when the parts are mating and one of them is connected to the other in a certain position. In this case, one of the details acts as a template. Pencil markings are made using a ruler on aluminum and duralumin blanks. When marking workpieces made of these materials, scribes are not used, since when the scratches are applied, the protective layer is destroyed and conditions are created for the appearance of corrosion. Marriage when marking, i.e. non-compliance of the dimensions of the marked workpiece with the drawing data, arises due to the inattention of the marker or inaccuracy of the marking tool, the dirty surface of the plate or the workpiece.

Metal cutting.

Metal cutting- this is an operation in which excess metal layers are removed from the surface of the workpiece or the workpiece is cut into pieces. Cutting is carried out using a cutting and percussion tool. A chisel, a cross cutter and a groove cutter are used as cutting tools. The percussion tool is a metalwork hammer. Purpose of felling: - removal of large irregularities from the workpiece, removal of hard crust, scale; - punching out keyways and lubrication grooves; - cutting edges of cracks in parts for welding; - cutting off the heads of the rivets when they are removed; - punching holes in sheet material. - cutting of bar, strip or sheet material. The felling can be fine and rough. In the first case, a layer of metal 0.5 mm thick is removed with a chisel in one pass, in the second - up to 2 mm. The processing precision achieved during felling is 0.4 mm.

Editing and straightening.

Straightening and straightening- operations for straightening metal, blanks and parts with dents, waviness, curvatures and other defects. Straightening can be done manually on a steel straightening plate or cast-iron anvil and by machine on straightening rollers, presses and special devices. Manual straightening is used when processing small batches of parts. Enterprises use machine straightening.

Flexible.

Bending- an operation, as a result of which the workpiece takes the required shape and dimensions due to stretching of the outer layers of the metal and compression of the inner ones. Bending is carried out manually with hammers with soft strikers on a bending plate or with the help of special devices. Thin sheet metal is bent with mallets, wire products up to 3 mm in diameter - with pliers or round-nose pliers. Only plastic material is bent.

Cutting.

Cutting (cutting)- division of bar or sheet metal into parts using a hacksaw blade, scissors or other cutting tool. Cutting can be carried out with or without chip removal. When cutting metal with a hand hacksaw, shavings are removed on hacksaw and cut-off lathes. Cutting of materials with manual lever and mechanical shears, press shears, nippers and pipe cutters is carried out without removing chips.

Dimensional processing.

Metal filing.

Filing- an operation to remove a layer of material from the surface of the workpiece using a cutting tool manually or on filing machines. The main working tool for filing is files, files and rasps. With the help of files, flat and curved surfaces, grooves, grooves, holes of any shape are processed. The precision of filing is up to 0.05 mm.

Hole machining

When machining holes, three types of operations are used: drilling, countersinking, reaming and their varieties: reaming, countersinking, counterbore. Drilling- operation for the formation of through and blind holes in a solid material. It is carried out using a cutting tool - a drill that performs rotational and translational movements relative to its axis. Purpose of drilling: - obtaining irrelevant holes with a low degree of accuracy and a class of roughness of the machined surface (for example, for fastening bolts, rivets, studs, etc.); - making holes for threading, reaming and countersinking.

Reaming- an increase in the size of a hole in a solid material obtained by casting, forging or stamping. If a high quality of the machined surface is required, then the hole after drilling is additionally countersinked and reamed.

Countersinking- processing of cylindrical and conical pre-drilled holes in parts with a special cutting tool - a countersink. The purpose of countersinking is to increase the diameter, improve the quality of the machined surface, increase accuracy (reduce taper, ovality). Countersinking can be the final operation of the hole or intermediate before reaming the hole.

Countersinking- this is the processing with a special tool - countersink - of cylindrical or conical grooves and chamfers of drilled holes for the heads of bolts, screws and rivets. Counterbore is performed with counterbore for cleaning the end surfaces. Bosses for washers, thrust rings, nuts are processed with counterbeds.

Deployment- This is the finishing of the holes, providing the highest accuracy and surface cleanliness. The holes are reamed with a special tool - reamers - on drilling and lathes or manually.