The marking is planar. Drawing the image on the workpiece Drawing on the workpiece the contours of the future product
Section 2. The manufacturing technology of products from sheet metal and wire
Theme 2.1. The process of marking blanks on sheet metal
§ 7. TECHNOLOGY OF LABELING OF BILLETS ON SHEET METAL
1. Remember what technological process is called rozmіchannyam.
2. What line is called the base?
3. What is an allowance? What is it for?
4. What device is called a template? What is his purpose?
5. Is a graphic document called a routing? What is it for?
The technological operation of applying marking lines or marks on the workpieces, determine the location of the technological operations defined by a graphic document, called rozmіchannyam.
Pegging is a very responsible operation. The quality of the future product depends on how accurately it is performed.
For marking, the workplace is equipped with rozmichalnymi plates - thick smooth and clean metal plates (Fig. 60).
Fig. 60. Types of screed plates
The error obtained with conventional marking methods can be approximately 0.5 mm.
To choose the right blank for the manufacture of the product, you must carefully study the drawing of the part and determine the allowance for processing. Then, if necessary, the workpiece is straightened (level the surface). You will learn about the indicated technological operation from the following paragraphs.
After the workpiece is aligned, its marking begins. In order to make marking lines (contours) better visible when using rosemary, the metal workpiece is cleaned of dirt and rust with a metal brush or sandpaper on a paper or fabric basis.
Then, for better visibility of the marking lines, the surface of the workpiece can be coated with chalk solution, if necessary.
The markings are carried out with special tools (fig. 61). Each of them is designed to perform certain technological operations.
For marking straight lines, measurement and deposition on the workpiece dimensions use a metal scale ruler.
Drawing of lines and lines on metal, plastic and other surfaces is carried out with a drawing machine. They make it from steel wire, temper it and hone it.
Layout of the workpiece begins with the application of baselines, from which the dimensions are laid off and the contours of the future product are marked out. The first of them is carried out at a distance of 3 ... 5 millimeters from the long edge of the workpiece. To do this, a scale ruler, for example, by the fifth stroke, is combined with the base edge first to the right and a line is drawn at the end edge of the ruler with a drawing tool.
Fig. 61. Marking bench tools: a - scale ruler; b - drawing; in - punch; - metalwork compass; d - metalwork square
In the same wayperform a stroke to the left of the base edge. Next, the line is applied exactly to the risks applied to the right and left, and the drawing box is in such a position that its tip exactly matches the drawn lines (Fig. 62, a, b).
Fig. 62. Snoozing dimensions with a ruler
Only under this condition mark the baseline, connecting both dashes (Fig. 62, c). The greater the distance between the lines, the more accurate is the parallelism of the lines (Fig. 63).
During the drawing, the drawing machine is kept inclined from the ruler in the direction "towards itself" at an angle of 45 ... 70 ° (Fig. 64).
Applying a square to the baseline, draw a second baseline at an angle of 90 ° to the first 3 ... 5 mm from the short edge (Fig. 65). From these two lines should be postponed all the dimensions necessary for the manufacture of the product.
Using a center punch, mark the centers of arcs and circles, and the places where holes are drilled. First, with the intersection of the two strips, mark the center of the future hole. Then, laying the blank on the screed plate, take the punch with three fingers of the left hand, put the sharp end at the point of intersection of the pictures and, straightening the punch perpendicular to the plane of the workpiece, outline the location of the hole with a light hammer blow on the center punch (Fig. 66). The cavity that remained on the surface of the workpiece is called a core, and the process is called core drilling.
Fig. 63. Baseline markings
Fig. 64. The correct position of the scriber when rozmіchannі
Fig. 65. Drawing a baseline using a square
Fig. 66. The sequence of kernivannya: a - markup; b - punching; c, d - adjustment of the perpendicularity of the punch; d - kernuvannya
A compass is used to mark arcs and circles. First mark the center of the circle and tilt it. Then one leg of the marking compass is installed in the core, and the second is marked with an arc or circle of the desired radius (Fig. 67).
For marking a large number of parts of the same shape and size, templates and stencils are used (Fig. 68).
Marking of metal billets is carried out on a bench with a marking plate or in a separate workplace intended for marking.
The instruments are placed according to the already known rules: those that are used most often are located closer, the instruments that are taken with the right hand (drawing tool, compasses, etc.) are placed on the right, and those that are taken with the left hand are placed on the left.
Misuse of the instruments is not permitted, as this may lead to their damage and the inability to perform accurate measurements.
After completion of the work, the measuring and marking tools are cleaned of dirt and stored in designated places for them in special cases or stackings.
During operation with a retail tool, the following safety rules must be observed:
1. Work associated with the use of tools with piercing and / or cutting parts should be performed in mittens.
2. During breaks between work at the tip of the drawing machine, it is necessary to put on safety caps or place them in special pads.
Fig. 67. Marking with a metal compass
3. It is necessary to prevent slipping of the workpiece, the edges of which can cause injury.
4. Transfer the drawing tool or the cutting tool with the tip “to you”, and the brothers with the tip “from yourself”.
Rice, 68. Tools for marking: a - templates; b - stencils
PRACTICAL WORK No. 6
Product Markings
Equipment and materials: a set of equal blanks from sheet metal, a bench scale, a drawing machine, a scribe, a center punch, a hammer.
Work sequence
1. On the instructions of the teacher or in accordance with graphic images of approximate objects of labor, the sweeps of which you performed while studying the section “Unfolding the surfaces of geometric bodies”, re-familiarize yourself with their design features (see Fig. 54).
2. Determine from the specified list or prepare, at your own request, a sketch of the future product or find another object of labor in information sources.
3. Include, as you wish, adjustments to the external shape or design of the objects selected for the manufacture of labor.
4. Prepare a workpiece of the appropriate size.
5. Define the base edge and draw base lines.
6. Mark the contours of the future product with a machining allowance.
7. Designate, if necessary, the location of the holes and hole them.
8. Check the quality of the markup.
9. Further completion of the final technological operations is carried out after studying the relevant topics in the following lessons.
Straightening, direction, marking, drawing, drawing, center, bending line, sweep.
Kerner - a short steel rod with a hardened conical point for marking parts.
1. What tools are used for the production of blanks on sheet materials?
2. What is the technology for marking parallel lines?
3. What is the difference between the marking technology on wood and the marking on metal?
4. What is the sequence of marking blanks using a marking compass?
5. From which line do the workpiece layout begin? What is the sequence of its markup?
6. In what cases are templates used?
7. What is the technology for pinning hole centers?
8. Why is there an allowance on the workpiece?
9. What tool is used for soft metal rozmichannі?
Test tasks
1. What units indicate the dimensions on the engineering drawings?
A meter
In centimeters
To decimeters
G millimeters
2. What parameters determine the accuracy of a bench scale?
And the length of the measuring scale
Would the thickness of the strokes plotted on the measuring scale
In the graduation price of the measuring scale
D all listed
D there is no correct answer
3. What serves as a guide for the procurement of rozmіchannі?
A long edge
Would be shorter edge
In baseline
4. For which process operation is the stock assigned?
A finish
B finishes
In final processing
G grinding
D filing
5. What tool is used for marking a large number of identical parts?
A ruler
Would corner
To the drawing room
Benchmarking
TO category:
Markup
Benchmarking
Marking is the process of transferring the shape and dimensions of a part or part thereof from a drawing to a workpiece. The main purpose of the markup is to identify the places and boundaries of processing on the workpiece. Locations are indicated by the centers of the holes obtained by subsequent drilling, or by bending lines. The processing boundaries separate the material that must be removed from the material that remains and forms the part. In addition, marking is used to verify the size of the workpiece and its suitability for the manufacture of this part, as well as to control the correct installation of the workpiece on the machine.
Processing blanks can be done without marking, using conductors, stops and other devices. However, the cost of manufacturing such devices is paid back only in the production of serial and mass parts.
Marking (which is essentially close to technical drawing) is performed using special tools and devices on the surfaces of the workpieces of parts. Marking risks, i.e., lines drawn on the surface of the workpiece, indicate the boundaries of processing, and their intersections - the positions of the centers of the holes or the position of the centers of the arcs of the circles of the mating surfaces. For marking risks, all subsequent processing of the workpiece is performed.
The marking is mechanized and manual. Mechanized marking performed on coordinate boring machines or other devices that ensure accurate movement of the workpiece relative to the marking tool, is used for large, complex and expensive workpieces. Manual marking is performed by toolmakers.
There are surface and spatial markings. Surface marking is performed on one surface of the workpiece, without linking its individual points and lines with points and lines lying on another surface of this workpiece. In this case, the following methods are used: geometric constructions; according to the template or sample of the part; using devices; on the machine. The most common type of surface marking is planar, used in the manufacture of flat gauges, conductive plates, stamp parts, etc.
Spatial marking is performed by linking the dimensions between points and lines lying on different surfaces of the workpiece. The following methods are used: for one installation; with rotation and installation of the workpiece in several positions; combined. Spatial marking is used in the manufacture of parts of complex shape.
Marking tools and devices. According to its purpose, the marking tool is divided into the following types:
1) for drawing and drawing depressions (scriber, thicknesses, compasses, center punches);
2) for measuring and controlling linear and angular quantities (metal rulers, calipers, squares, micrometers, precision squares, angle meters, etc.);
3) combined, allowing measurements and risks (marking calipers, calipers, etc.).
Scriber marks are used to apply marks on the surface of the workpieces. Steel markers are used for marking unprocessed or pre-machined surfaces of workpieces, brass markers are used for marking polished and polished surfaces, and soft pointed pencils are used for marking precise and finished surfaces of non-ferrous workpieces.
The marking compasses according to the device and purpose correspond to the drawing ones and are used to draw circles and divide them into parts, transfer linear dimensions, etc.
Fig. 1. Marking tool: a - scriber, b - compasses, c - punch, d - square
The steel legs of the chertilki and compasses are made of U7 and U8 steels (the working ends are hardened to 52-56 HRC3) and from VK.6 and VK8 hard alloys. The working ends of the scriber and compasses sharpen sharpened. The thinner and harder the tips of these tools, the finer the risks and the more accurately the part will be manufactured.
The punch (Fig. 1, c) is used to apply recesses (cores) on the marking risks. This is necessary so that marking risks, even being erased, are noticeable during the processing. Kerner - a steel round rod made of alloyed (7ХФ, 8ХФ) or carbon (U7A, U8A) steel. Its working part is hardened and sharpened at an angle of 609. The center punch head, on which it strikes with a hammer, is rounded or chamfered and also hardened.
The Reysmass used for spatial marking for conducting horizontal marks on the marked surface and for checking the position of the workpiece on the marking plate is made in the form of a rack on which the scriber can be moved in height and fixed in the required position. In the simplest reysmass in design, the scriber is set to the required height on a vertical scale ruler or using end measures. In tool production, we usually use stengenreysmasy, and sometimes (if necessary) and special design reamers (for example, a multi-strand reamer with several scriber bars on the rack, independently set in height by a given size). Combined gages are also used, that is, regular gages, equipped additionally with various devices and tools (for example, a gusset with a center finder).
The square is used for drawing lines, building corners and checking them.
The vernier caliper serves to measure the dimensions of the external and internal surfaces and to conduct marking marks. It differs from a conventional caliper in the presence of carbide sharp-pointed tips on its lips.
The devices used for marking and used to install, align and fix workpieces include adjustable wedges, prisms, linings, jacks, chucks, collets, rectangular magnetic plates, rotary tables, sinus tables, dividing heads, and many others.
Auxiliary materials are used to prepare the surfaces of the workpiece for marking. The workpieces are cleaned of dust, dirt, rust, scale and oil with steel brushes, files, a sanding cloth, wiping ends, napkins, brushes, etc. layer. The paint should adhere well to the surface, dry quickly and remove well. Unprocessed or rough surfaces of steel and cast iron billets are painted with chalk dissolved in water with the addition of wood glue and turpentine (or linseed oil and desiccant). Pre-treated surfaces are coated with copper sulfate solution. Large sized machined surfaces and aluminum alloys are coated with special marking varnish. For this purpose, you can use a solution of shellac in alcohol, colored with fuchsin. Staining of small surfaces is done by cross-brush movements. Large surfaces are spray-painted. The painted surface is dried.
The sequence of work when marking. Layout includes three stages: preparation of blanks for marking; the actual markup and quality control markup.
Preparation of the blank for marking is performed as follows:
1. Carefully study and verify the detail drawing.
2. Preliminary inspect the workpiece, identify defects (cracks, scratches, shells), control its size (they should be sufficient to produce parts of the required quality, but not excessive).
3. Clean the workpiece from dirt, oil, traces of corrosion; paint and dry the surfaces of the workpiece on which the marking will be made.
4. Select the base surface from which the dimensions will be laid, and prepare them. If the edge of the workpiece is selected as the base - it is pre-aligned, if two mutually perpendicular surfaces - they are processed at right angles. Base lines are already applied during the marking process. The location of the bases should ensure that the part fits into the workpiece contour with the smallest and most uniform allowance.
Actually markup is performed in the sequence determined by the markup method. When marking according to the template, the latter is installed on the workpiece, correctly oriented relative to the bases, and fixed. The template should fit snugly to the workpiece over the entire contour. Then, the outline of the template on the blank is drawn with a scriber and the template is unfastened.
Marking by the method of geometric constructions is carried out as follows. First, they carry out (relative to the base) all horizontal, and then all vertical marking risks; then all roundings, circles are made and connected by straight or inclined lines.
When marking, the rack of the thickness gauge is taken for the base and moved along the marking plate relative to the surface of the workpiece, while avoiding skewing. The reamer scriber touches the vertical surface of the workpiece and leaves horizontal risk on it. The scriber should be at an acute angle to the direction of travel, and the pressure on it should be small and uniform. Risks are conducted parallel to the working surface of the scribe. In order for the risks to be strictly linear and horizontal, the supporting surfaces of the surface gage and screed must be machined with great accuracy. The marking quality is improved if a flat scriber is used in the planer.
Quality control of marking and core n and e is the final stage of marking. The core centers should be located exactly according to the marking risks, the core should not be too deep and differ from each other in size. At direct risks, cores are punched at distances of 10-20 mm, at curved - 5-10 mm. The distances between the cores are the same. With increasing dimensions of the workpiece, the distance between the cores also increase. The points of intersection and intersection of the marking patterns must be corrupted. On the machined surfaces of precision products, marking risks do not corrode.
Marriage with markup can lead to significant material losses. Its most common causes are: the wrong choice of bases and their poor preparation; errors in reading the drawing, when deferring dimensions and in calculations; wrong choice of marking tools, devices, their malfunction; wrong markup methods and techniques.
The widespread use of mechanized marking tools and devices increases the quality and productivity of marking. Therefore, mechanical, electrical and pneumatic punch, calipers and caliper with electronic indication, mechanized devices for installing, aligning and securing workpieces should be widely used. Significantly speeds up the work and reduces the number of errors the use for calculating microcalculators. It is necessary to create more versatile and easy to use marking tools and devices. Where this is economically justified, coordinate machines, coordinate measuring machines should be used for marking, or marking should be excluded altogether by processing blanks on CNC machines.
Before processing materials (logs, beams, boards, bars, plywood, wood boards, etc.), as well as the blanks obtained from them, evaluate their quality, measure and mark. The marking consists in drawing lines (drawings) on the surface of the material or the workpiece, which determine the dimensions (shape contours and sizes) of the future workpieces or parts and elements of their joints according to the drawing. In this case, the size of the established allowances (stock sizes) for machining along the length, width and thickness of the workpiece, as well as impermissible defects and defects of wood are taken into account.
A part is a separate structural unit of a carpentry and carpentry or structure, made of a homogeneous material without the use of prefabricated operations. As a result of assembly (connection and fastening) of parts, assembly units (boxes, sashes, window transoms) and finished products (door and window blocks) are obtained.
The machining allowance is the difference between the dimensions of the workpiece and the part obtained from it. The size of the allowance for processing includes the width of the cut, which is produced by a saw when cutting material into workpieces. When marking, the moisture content of the wood used must be taken into account. If the moisture content of the wood is more than 20%, allowance should also be added for its shrinkage in width, length and thickness of the workpiece. The amount of wood drying along the length (along the fibers) is negligible.
In the manufacture of small parts, it is advisable to use blanks that are multiple in length, width and thickness. In this case, several single blanks are then obtained from one blank by cutting it. For multiple blanks, allowance for cuts must be taken into account for dividing them into single blanks. When marking wood-based panels, plywood and veneer produced in dry commercial presentation (humidity 8 ± 2%), their standard thickness is selected and allowances are taken into account only for processing along the length and width of the workpieces, as well as the width of the necessary cuts to produce single-time workpieces. Allowances for processing and drying of wood and processing of wood-based panels are regulated by standards.
Instrumentation and marking tools
To perform marking and control the accuracy of processing workpieces and parts, various tools, instruments and devices are used. Under the accuracy of processing understand the conformity of the form and dimensions of the manufacture of parts to the requirements of the drawing and technical conditions.
Proper marking provides the necessary accuracy in processing workpieces and parts and the economical use of materials. Linear dimensions are measured with a tape measure, meter tape measure, folding meter and different rulers with millimeter, centimeter, decimeter and meter divisions.
The square serves to check and set aside a right angle (90 °) when marking and processing materials and workpieces. Nonsense is designed for marking and controlling angles of 45 ° and 135 °. It consists of a base to which wooden or metal is rigidly attached linearly at an angle of 45 °.
Malka is used to measure the sample and transfer them to the workpiece during marking. It has an articulated base and a ruler. Malka is wooden and metal.
The compasses carry the given sizes and describe the circles when they are marked. The inside diameter of a round hole is measured with a nutrometer. The outer diameter of a round part is determined using a caliper and a caliper, which are used to measure the small linear dimensions of the parts and the elements of their connections. Use a caliper with a bilateral arrangement of jaws for external and internal measurements (width and thickness of parts, thickness of shields and ridges, width of eyes) and a ruler to determine the depth of nests, grooves and holes. A caliper is a sliding metal tool that has a bar with a main scale, a frame with a clamping screw and an additional scale (cone), and a depth ruler. The frame can move along the bar depending on the size of the determined size. When measuring, first, whole millimeters are counted, which have passed along the bar to the leftmost line of the cone, and then - tenths of a millimeter by the complete coincidence of the cone division with any division of the rod. The caliper can be with a measurement accuracy of 0.1 to 0.05 mm.
The level is used to check the horizontal and vertical surfaces of the carpentry and structures (window and door blocks, beams and logs, floors, racks). It has a wooden or metal bar, in which an arched glass tube with alcohol and an air bubble is placed. If the edge of the level bar coincides with the horizontal or vertical position of the elements being checked, the air bubble will be located between the two marks on the tube. Braces mark spikes and eyes. It has a wooden block with a transverse quarter at one end.
Reysmus serves for applying marking marks parallel to one of the surfaces of the marked workpiece and to each other.
Plumb - used to verify the vertical installation of carpentry and structures. It consists of a cord with a load attached to it by a cylindrical metal pointed at the bottom.
A micrometer with a graduation scale of 0.01 mm is equipped with a bracket with a measuring heel, with a micrometer screw and a drum. The end surface of the screw facing the heel is a measuring one. The ratchet is designed to achieve a constant measuring force. Hundredths of a millimeter are counted on a drum circular scale. The pointer is a longitudinal held on the stem.
The goniometer is used to measure the angle of inclination of two adjacent surfaces. Goniometers are conical and optical. The goniometer with a cone allows you to determine the external angles from 0 to 180 ° and internal from 40 to 180 ° with an error of not more than ± 5 °. Optical goniometers are used to measure the angular parameters of the cutting part of the tools. They are equipped with a magnifying glass, this provides a reading of the values \u200b\u200bof the angles with an error of not more than 10 "(arc seconds).
Markup techniques
The markup is performed on a workbench, desktop or directly at a construction site. Marking lines are drawn with a pencil or beating with a deliberate cord, and the risks are carried out with an awl, scriber, a special oblique knife or a wide chisel. Hard pencils are used for marking hardwood. When marking non-planed lumber, it is better to use a carpentry or carpentry pencil, which has a thick core, and its cross section has an elliptical shape. Do not use chemical pencils that leave hard to wear marks on wood. When drawing a marking line, the pencil chamfer must be pressed to the edge of the guide tool (ruler, square, template).
To mark the circumference of the legs of the compass using a ruler or vernier caliper, extend the size of the radius of the circle. Find and mark the center of the circle by drawing two mutually perpendicular lines. Putting one leg of the compass in the center of the circle, the rotation of the other legs spend the risk of a given circle.
When performing carpentry, marking lines are applied by striking the surface of the material with a stretched cord, grated chalk or charcoal. You can use a staple to hold several short and parallel patterns.
Marking requires significant labor costs and a higher qualification of the worker, so you need to make templates and apply marking devices.
For marking use overhead templates for various purposes. They can have various shapes, sizes and designs (flat and box-shaped). Templates are made of boards, plywood, hard fiberboards or sheet metal. Templates should have contours (or cutouts) in the form of marked elements, joints of wooden parts. The template is applied to the workpiece to be marked, and then the necessary contours are drawn with a pencil or scriber.
Marking should be done correctly and accurately. It should ensure the receipt of high-quality workpieces and parts of the required shapes and sizes with the least complexity of their manufacture. When marking, it is necessary to provide for a rational consumption of materials with a minimum amount of wood waste generated (scraps, sawdust, shavings), strive to obtain the greatest useful yield of workpieces and parts from the used material.
Metal marking
TO category:
Markup
Metal marking
Marking is the operation of applying to the workpiece (forging, casting, rolling, etc.) rice (lines) for its subsequent processing. Risks can be contour, control and auxiliary.
Contour risks separate metal allowance from the metal of the finished part. In order for contour risks to be better distinguished and preserved during transportation and processing of the workpiece, they are cured, i.e., small conical recesses (cores) are applied along the pictures.
In subsequent processing, the stock is removed so that half of the contour risk width and half of each core recess (core) remain on the part. Contour risks are also used for the installation and alignment of workpieces on the machine.
Auxiliary risks are used to read the dimensions when marking and installing the workpiece on the machine.
Control risks are applied next to the contour at a distance of 5-10 mm. Being parallel (or concentric) contour, these risks make it possible at any time to check whether the installation is correct and the processing is correct (if for some reason the contour risk has disappeared).
Thus, the marking consists in drawing on the workpiece the lines necessary for processing the part. Before marking, those areas of workpieces where risks will be applied are painted so that risks and cores can be easily found. For painting, chalk with an admixture of glue diluted in water is most often used. The treated surfaces of steel and cast iron billets are sometimes coated with a solution of copper sulfate in water; this leads (as a result of the reaction of copper sulfate with iron) to form a thin layer of copper on the surface of the workpiece, on which marking risks are applied.
The markup is divided into planar and volumetric. Flat marking is performed on sheet material on one side (in one plane); with volumetric marking, risks are applied to two (or more) surfaces of the workpiece.
In modern engineering, they try to refuse marking as much as possible, since it requires a highly skilled workforce, and the accuracy of processing on it is small. However, this succeeds only in mass and large-scale production, where the marking can be completely or to a large extent eliminated through the use of special machines and devices that ensure the correct basing (installation) of the workpiece and guarantee receipt of the dimensions of the parts in the established tolerances. With a single and small-scale production, the cost of manufacturing devices does not pay off, so the processing of parts is carried out according to the markup. The lack of accuracy of the parts processed according to the marking makes them resort to their individual fit during assembly. For marking, workpieces are mounted on screed plates. The upper (working) plane of the plate on which the workpieces and marking tools are installed, and its side faces are precisely machined (planed).
Often, narrow and shallow, mutually perpendicular grooves are spread along the upper plane of the slab so that squares with a side of 200 to 500 mm are formed. These grooves in many cases facilitate the installation of workpieces and fixtures on the plate. The dimensions of the plates vary widely from 750 X 750 to 4000 X X 6000 mm; larger plates (for marking very large workpieces) are made up of several plates and installed on the foundation.
As marking tools, scale rulers, thicknesses, squares, compasses, punch punches, etc. are used.
A scale bar is used to measure dimensions; it is fixed on the square so that its end (zero stroke) touches the working surface of the plate.
The surface gage is used for applying to the workpiece risks parallel to the working plane of the scribe. When working with a thickness gauge, the base is moved along the slab, and risks are applied to the needle installed on a scale on a scale in height.
A hand needle or scriber is used to draw lines along a ruler, square or pattern.
Fig. 1. Scale bar attached to a square
Fig. 2. Marking surface gage
Fig. 3. Hand needle (scriber)
Fig. 4. Malka
The square is used for drawing vertical scriber with scriber and for checking the vertical position of any plane of the workpiece, as well as for constructing right angles.
Malka and the goniometer are used for applying padded patterns and controlling the installation of the workpiece on a scribe. The ruler is set to the desired angle by the protractor or goniometer. After installation, the ruler is fixed by turning the lamb.
The marking compass is used for drawing pictures of circles and arcs, as well as for laying off the sizes taken on a scale ruler. In some cases, a caliper is also used to mark circles and arcs.
The square-center detector is used to apply diametrical patterns on the ends of the shafts and, accordingly, to find the centers on the ends. The center-detector square consists of a square and a ruler attached to it, the working edge of which divides the angle of the square in half. For marking, a square is applied to the workpiece and, according to the ruler, is applied with a scriber to risk. To find the center of the workpiece, a second risk is applied after turning the square at a certain angle.
Fig. 5. Marking compass
Fig. 6. Square-center detector
Fig. 7. Kerner
The center punch is used to apply cores on risks or to mark the centers of holes.
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Markup
When marking, the surface of the sheet metal is applied marking lines (the risks) using marking tools and devices. The figure shows the tools for marking blanks of sheet metal - scriber (sharpened steel bar), marking compass.
Markup can be done with template - flat sample parts. The template is pressed to the surface of the workpiece (a clamp can be used for this case) and the outline is drawn with a scriber, tightly pressing the point of the scriber to the edge of the template.
The marking of rectangular parts according to the drawing (sketch) begins with the definition of the base edge of the workpiece and the application of the basic risks. The most even edge of the workpiece is selected as the base for the marking. From her lead marking: conduct the basic risk on the line (Fig. a), along the square they conduct the second risk at an angle of 90 ° (Fig. 6 ), set aside size A in a ruler (Fig. in), on the square they carry out the third risk (Fig. g) set aside size B (fig. d) and on the square conduct the fourth risk (Fig. e).
The point of the scriber should be firmly pressed to the ruler, and she herself is tilted in the direction of movement. The risk must be applied once. The scribe's edge is pressed against the ruler or template, but not vertically (see figure to the right).
The figure below shows the markup with punch and marking compass. With a light blow of the hammer on the center punch, the workpiece is applied ( screw up) centers of arcs and circles. 
In these centers, the leg of the marking compass is installed. When marking, the compasses are slightly tilted in the direction of movement, and the force is applied to that leg, which is located in the center of the circle.
Before marking, it is necessary to clean the workpiece from dust, dirt, traces of corrosion and check the serviceability of marking tools.
Markup is a very responsible operation. The quality of the future product depends on how accurately it is performed.
You can not draw the scriber in the same place more than once.
Handle the scriber very carefully so as not to injure your eyes or hands. It must be served with a pen away from you, and put on the workplace with a pen toward you.
You can not put the scriber in the pocket of your bathrobe, you can only keep it on the table.
In production, manual marking is used in the manufacture of templates, models, product samples. In tool shops, marking is performed on special boring machines. At the enterprises markup is busy metalworkers. Templates are made by highly qualified toolmakers.