Marking is used mainly in single and small-scale production. In large-scale and mass production factories, there is no need for markings due to the use of special devices - jigs, stops, etc.

Depending on the shape of the marked blanks and parts, marking is divided into planar And spatial(volumetric).

Planar marking, usually performed on the surfaces of flat parts, on strip and sheet material, consists of applying contour parallel and perpendicular lines (marks), circles, arcs, angles, axial lines, various geometric shapes according to given dimensions or contours of various holes according to specified dimensions to the workpiece. templates.

Figure 3.1.1 Planar marking (Makienko N.I. General course in plumbing M.: Higher school, 1989.)

Using planar marking techniques, it is impossible to mark even the simplest body if its surfaces are not straight. At planar marking impossible to apply to lateral surface the cylinder has horizontal marks perpendicular to its axis, since it is impossible to attach a square and a ruler to this surface. But even if there were a flexible ruler that could be wound around the surface of the cylinder, then applying parallel marks to the cylinder would present great difficulties.

Spatial marking is most common in mechanical engineering; in its techniques it differs significantly from the planar one. The difficulty of spatial marking lies in the fact that you have to not only mark individual surfaces of the part located in different planes and under different angles to each other, but to link the markings of these individual surfaces with each other.

Planar marking is used when processing sheet material and rolled profiles, as well as parts on which marking marks are applied in one plane.

Figure 3.1.2 Spatial marking (Makienko N.I. General course in plumbing M.: Higher school, 1989.)

Spatial marking- this is the application of marks on the surfaces of the workpiece, interconnected by mutual arrangement.

When marking, various measuring and special marking tools are used. To improve the visibility of the marking lines, a series of shallow dots should be knocked out on them using a center punch at a short distance from each other. Marking is most often done on special cast iron marking plates.

In the serial production of parts, it is much more profitable to use instead of individual markings copying.

Copy(basting) - applying the shape and dimensions to a workpiece according to a template or finished part.

The copy operation is as follows:

• a template or finished part is applied to a sheet of material;
• the template is fastened to the sheet using clamps;
• the outer contours of the template are outlined;
• To improve the visibility of the lines, inking is done.

Templates are made according to sketches, taking into account all types of allowances. The material for the templates can be sheet steel, tin, or cardboard. The method of arranging blank parts on a material is called let's reveal.

There are three main ways to cut sheets:

1. Individual cutting, in which the material is cut into strips for the production of parts of the same name (plates for stamping Raschig rings, strips for heat exchanger gaskets).
2. Mixed cutting, in which a set of parts is marked on a sheet. Mixed cutting allows you to save metal, but at the same time, labor intensity increases, as the number of operations and equipment changeovers increases.

For mixed cutting, cutting cards are developed, which represent sketches of the placement of parts on metal, drawn to scale on a sheet of paper. Cutting cards are compiled in such a way as to place on the sheets the entire set of parts necessary for the manufacture of assemblies and ensure the most rational and convenient cutting of workpieces. Figure 3.1.3 shows an example of cyclone cutting cards, from which it can be seen that correct cutting ensures straight cutting.

Figure 3.1.3 Cutting cards: a - correct cutting; b - irrational cutting (Technology for manufacturing the main parts of equipment Directory Baku 2010)

1. Group cutting. With this type of cutting, large blanks are first cut from the sheet, medium-sized parts are cut from waste, and scraps are used for small parts. This cutting is the most progressive for single production.

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

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

Spatial marking most common in mechanical engineering and differs significantly from planar. 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 markings of these surfaces with each other.

Base- a base surface or baseline from which all dimensions are measured when marking. It is selected according to the following rules: if the workpiece has at least one machined surface, it is selected as the base; If there are no machined surfaces on the workpiece, the outer surface is taken as the base surface.

Preparing 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 the part is free of holes, cracks, burrs and other defects. To paint the surfaces of the workpiece before marking, use the following compositions: chalk diluted in water; ordinary dry chalk. Dry chalk is used to rub the marked untreated surfaces of small non-critical workpieces, since this coloring is fragile; solution copper sulfate; alcohol varnish is used only for precise marking of the surfaces of small products. The choice of coloring composition for application to the base surface depends on the type of workpiece material and the method of its preparation: the 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 ferrous metal workpieces are painted with a solution of copper sulfate, which, when interacting with the workpiece material, forms a thin film on its surface pure copper and ensures clear identification of marking marks; the treated surfaces of non-ferrous metal workpieces are painted with quick-drying varnishes.

Marking methods

Template marking is used in the production of large batches of parts of the same shape and size, and sometimes for marking small batches of complex workpieces. Marking according to a sample is used during repair work, when dimensions are taken directly from a failed part and transferred to the material being marked. This takes wear and tear into account. A sample differs from a template in that it has a one-time use. Marking in place is carried out when the parts are mating and one of them is connected to the other in a certain position. In this case, one of the parts acts as a template. Markings with a pencil are made using a ruler on blanks made of aluminum and duralumin. When marking workpieces made from these materials, scribers are not used, since the marks are destroyed when applied. protective layer and conditions are created for corrosion to occur. Defects in marking, i.e. Non-compliance of the dimensions of the marked workpiece with the data in the drawing occurs due to the inattention of the marker or the inaccuracy of the marking tool, or a dirty surface of the slab or workpiece.

Metal cutting.

Metal cutting is an operation in which excess layers of metal are removed from the surface of the workpiece or the workpiece is cut into pieces. Chopping is carried out using cutting and impact tools. The cutting tools for chopping are a chisel, a crosspiece and a groover. Percussion tool - plumber's hammer. Purpose of cutting: - removal of large irregularities from the workpiece, removal of hard crust, scale; - cutting out keyways and lubrication grooves; - cutting edges of cracks in parts for welding; - cutting off the heads of rivets when removing them; - cutting holes in sheet material. - cutting of rod, strip or sheet material. The cutting can be fine or 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 accuracy achieved when cutting is 0.4 mm.

Editing and straightening.

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

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 metal and compression of the inner ones. Bending is performed manually using hammers with soft strikers on a bending plate or using special devices. Thin sheet metal is bent with mallets, wire products with a diameter of up to 3 mm are bent with pliers or round nose pliers. Only plastic material is subject to bending.

Cutting.

Cutting (cutting)- dividing 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 saw, on hacksaw and cutting-off lathes, chips are removed. Cutting materials with manual lever and mechanical scissors, press shears, wire cutters 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 a workpiece using a cutting tool manually or on filing machines. The main working tools for filing are files, needle files and rasps. Using files, flat and curved surfaces, grooves, grooves, and holes of any shape are processed. The accuracy of filing processing is up to 0.05 mm.

Hole machining

When processing holes, three types of operations are used: drilling, countersinking, reaming and their varieties: drilling, countersinking, counterbore. Drilling- an operation to form through and blind holes in a solid material. It is performed using a cutting tool - a drill, which makes rotational and translational movements relative to its axis. Purpose of drilling: - obtaining non-critical holes with a low degree of accuracy and roughness class of the machined surface (for example, for fastening bolts, rivets, studs, etc.); - obtaining holes for threading, reaming and countersinking.

Reaming- increasing the size of a hole in a solid material produced by casting, forging or stamping. If 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- countersink. The purpose of countersinking is to increase the diameter, improve the quality of the machined surface, and increase accuracy (reducing taper, ovality). Countersinking can be the final machining operation of a hole or an intermediate operation before reaming the hole.

Countersinking- this is the processing with a special tool - a countersink - of cylindrical or conical recesses and chamfers of drilled holes for the heads of bolts, screws and rivets. Countering is carried out using counterbores to clean the end surfaces. Counters are used to process bosses for washers, thrust rings, and nuts.

Deployment- This is the finishing of holes, providing the greatest accuracy and surface cleanliness. Reaming of holes is carried out with a special tool - reamers - on drilling and lathes or manually.

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Chapter XII

MARKING

§ 46. TYPES OF MARKING

A significant part of machine parts is made from blanks supplied in the form of castings, forgings or sectional material.

During subsequent processing of the workpiece to the size of the part indicated in the drawing, a certain layer of metal is removed.

In order to prevent errors in the manufacture of a part during processing, the dimensions of the part are laid out on the workpiece exactly according to the drawing and marked with lines (marks) indicating the processing boundaries to which the metal layer (allowance) should be removed.

The operation of applying marks that define the boundaries of processing is called marking.

There are two types of markup: planar and spatial.

Planar marking is carried out by applying marks on the surface of flat parts, sheet and strip metal, surfaces of cast and forged parts.

Spatial marking differs significantly from planar. The difficulty of performing this marking is that surfaces and lines lying in different planes and at different angles are interconnected by a certain position in space.

The choice of marking method is determined by the shape of the workpiece, the required accuracy and the number of products to be manufactured. In practice, there are various marking methods: according to a drawing, a template, a sample and at a location.

Marking is carried out using special devices and tools: squares, protractors, calipers, height gauges, etc.

Marking marks serve as guidelines for correct installation workpieces on the machine and determining the amount of allowance for processing.

The accuracy of marking significantly affects the quality of processing. The degree of marking accuracy ranges from 0.25-0.5 mm. Errors made during marking usually lead to defects and damage to valuable material. In order to correctly mark, you need to have a good knowledge of drawing, be able to read drawings, and also correctly use marking tools and devices.

TO category:

Car maintenance

Main types of locksmith work

Marking
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Rice. 30. Marking plate

Marking is the drawing of boundaries on the surface of the workpiece in the form of lines and points corresponding to the dimensions of the part according to the drawing, as well as axial lines and centers for drilling holes.

If the marking is made in only one plane, for example on sheet material, then it is called planar. The marking of workpiece surfaces located at different angles to each other is called spatial marking. The workpieces are marked on a special cast iron plate (Fig. 30), called a marking plate, installed on a wooden table so that its upper plane is strictly horizontal.

Tools for marking and. When marking, use various marking tools.

The scriber (Fig. 31) is a steel rod with sharp, hardened ends. A scriber draws thin lines on the surface of the workpiece using a ruler, template or square.

Reismas is used for application on the workpiece horizontal lines, parallel to the surface of the marking plate. Reismas (Fig. 32) consists of a base and a stand fixed in its center, on which there is a movable clamp with a scriber that rotates around its axis. The movable clamp can move along the stand and be secured to it in any position with a clamping screw.

Rice. 31. Scribbler

The marking compass (Fig. 33) is used for drawing circles and curves on the workpiece to be marked.

Rice. 32. Reismas

Rice. 33. Marking compass

For precise marking, use a height gauge (Fig. 34). A rod with a millimeter scale is firmly fixed on a massive base. A frame with a vernier and a second micrometric feed frame move along the rod. Both frames are secured to the rod with screws in any desired position. The replaceable scriber leg is attached to the frame with a clamp.

Marking calipers are used for drawing circles of large diameters with direct setting of dimensions. A marking caliper (Fig. 35) consists of a rod with a millimeter scale printed on it and two legs, of which the leg is fixedly mounted on the rod, and the leg is movable and can be moved on the rod. The movable leg has a vernier. Hardened steel needles are inserted into both legs. The needle of the movable leg can be moved up and down and secured with a screw in the desired position.

Rice. 34. Height gauge

Rice. 35. Marking caliper

Rice. 36. Center finder

The center finder is designed to determine the center of the end of a cylindrical workpiece (Fig. 36). The center finder consists of a square with shelves located at an angle of 90° to each other, and a leg, the inner side of which divides the right angle of the square in half. To determine the center, the center finder is installed so that the flanges of the square touch the cylindrical surface of the workpiece. A scriber is drawn along the inside of the leg, thus marking a diameter line, then the center finder is turned 90° and a second diameter line is drawn. The intersection point of these lines will be the center of the end of the cylindrical workpiece.

A scale altimeter (Fig. 37) is used for marking in cases where it is necessary to set the tip of the scriber at a certain height. It consists of a fixed scale ruler attached to a cast iron square, a movable ruler moving along guide bases, and a sighting slide with a fine line. When marking, the sighting slider is installed so that its thin line coincides with the main axis of the workpiece, and is secured in this position. After this, the zero division of the movable ruler is placed against the thin line of the sighting slider and the distance (height) from the main axis of the workpiece to the other axes is read on the movable ruler.

The punch is used to make small indentations on the marking lines of the workpiece, so that these lines are clearly visible and are not erased during the processing of the workpiece. The center punch (Fig. 38) is made of tool steel in the form of a rod, the middle part of which has a notch. The working part of the lower end of the punch is sharpened at an angle of 45-60° and hardened, and the upper end is a striker, which is hit with a hammer when punching.

Devices for marking. In order to protect the surface of the marking plate from scratches and nicks, as well as to create a stable position when marking parts that do not have a flat base, and to facilitate the marking process, cast iron linings (Fig. 39, a) and jacks (Fig. 39) are used , b) and marking boxes (Fig. 39, c) of various shapes. Squares, clamps and adjustable wedges are also used.

The marking process is carried out as follows. The surfaces of the marked workpieces are cleaned of dirt, dust and grease. Then cover with a thin layer of chalk diluted in water with the addition of linseed oil and drier or wood glue. Well-treated surfaces are sometimes coated with a solution of copper sulfate or quick-drying paints and varnishes. When the applied layer of chalk or paint has dried, you can begin marking. Marking can be done according to a drawing or template.

Rice. 37. Scale altimeter

Rice. 38. Kerner

The process of marking the workpiece according to the drawing is performed in the following sequence:
– the prepared workpiece is placed on the marking plate;
– main lines are drawn on the surface of the workpiece, from which the position of other lines or centers of holes can be determined;
– draw horizontal and vertical lines in accordance with the dimensions of the drawing, then find the centers and draw circles, arcs and inclined lines;
– small depressions are knocked out using a center punch along the marked lines, the distance between which, depending on the condition of the surface and the size of the workpiece, can be from 5 to 150 mm.

Rice. 39. Marking devices:
a - linings, b - additional frames, c - marking boxes

When marking identical parts planarly, it is more advisable to use a template. This method of marking consists in placing a steel template on the workpiece and using a scriber to trace its contours on the workpiece.

Metal cutting

Bench cutting is used to remove excess metal in cases where great processing precision is not required, as well as for rough leveling of rough surfaces, for cutting metal, cutting down rivets, for cutting out keyways, etc.

Chopping tools. Tools for chopping metal are chisels and cross-cutters.” percussion instrument- hammer.

The chisel (Fig. 40, a) is made of tool steel U7A and, as an exception, U7, U8 and U8A. The width of the chisel blade is from 5 to 25 mm. The sharpening angle of the blade is selected depending on the hardness of the metal being processed. For example, for cutting cast iron and bronze, the sharpening angle should be 70°, for cutting steel 60°, for cutting brass and copper 45°, for cutting aluminum and zinc 35°. The chisel blade is sharpened on an emery wheel so that the chamfers have the same width and the same angle of inclination to the chisel axis. The sharpening angle is checked with a template or protractor.

Rice. 40. Tools for chopping metal:
a - chisel, b - crossmeisel, c - metalworker's hammer

Kreutzmeisel (Fig. 40, b) is used for cutting keyways, cutting rivets, and preliminary cutting grooves for subsequent cutting with a wide chisel.

To prevent the crosspiece from jamming when cutting narrow grooves, its blade should be wider than the drawn part. The sharpening angles of the crossmeissel blade are the same as those of the chisel. Crossmeisel length is from 150 to 200 mm.

Bench hammer (Fig. 40, b). When chopping, hammers weighing 0.5-0.6 kg are usually used. The hammer is made from tool steel U7 and U8, and its working part is subjected to heat treatment (hardening followed by tempering). Hammers come with round and square heads. Hammer handles are made of hardwood (oak, birch, maple, etc.). The length of the handles of medium-weight hammers is from 300 to 350 mm.

To increase labor productivity, cutting has recently begun to be mechanized by using pneumatic hammers operating under the influence of compressed air supplied from a compressor unit.

The manual cutting process is as follows. The workpiece or part to be chopped is clamped in a vice so that the cutting marking line is at the level of the jaws. Chopping is carried out in a chair vice (Fig. 41, a) or, in extreme cases, in a heavy parallel vice (Fig. 41.6). When chopping, the chisel should be in an inclined position to the surface of the workpiece being cut at an angle of 30-35°. The hammer is struck in such a way that the center of the hammer striker hits the center of the chisel head, and you only need to look carefully at the chisel blade, which should be moved exactly along the marking line for cutting the workpiece.

Rice. 41. Vise:
a - chair, 6 - parallel

When chopping, a thick layer of metal is cut down with several passes of the chisel. To remove metal with a chisel wide surface First, the grooves are cut out with a cross-section, then the resulting protrusions are cut off with a chisel.

To facilitate work and obtain a smooth surface when cutting copper, aluminum and other viscous metals, periodically moisten the chisel blade with soapy water or oil. When cutting cast iron, bronze and other brittle metals, chipping often occurs on the edges of the workpiece. To prevent chipping, chamfers are made on the ribs before cutting.

Is the sheet material cut on an anvil or on a slab with a chisel with a rounded blade, and do I do it first? cut with light blows along the marking line, and then cut the metal with strong blows.

The main equipment of a mechanic's workplace is a workbench (Fig. 42, a, b), which is a strong, stable table with a height of 0.75 and a width of 0.85 m. The cover of the workbench must be made of boards with a thickness of at least 50 mm. The top and sides of the workbench are covered with sheet steel. A chair or heavy parallel vice is installed on the workbench. The table has drawers for storing metalwork tools, drawings and workpieces and parts.

Before starting work, the locksmith must check the locksmith tools. Defects found in tools are eliminated or the unusable tool is replaced with a serviceable one. It is strictly forbidden to work with a hammer with a slanted or knocked-down surface of the striker, or to use a chisel with a slanted or knocked-down head.

Rice. 42. Mechanic's workplace:
a - single workbench, b - double workbench

To protect the eyes from fragments, a mechanic must wear glasses when working. To protect others from flying fragments, install a metal mesh. The workbench should be firmly placed on the floor and the vice should be firmly secured to the workbench. It is impossible to work on poorly installed workbenches, as well as on weakly secured vices, as this can lead to injury to the hand, and also quickly tires.

Metal straightening and bending

Mechanical straightening is usually used to straighten the curved shape of workpieces and parts. Straightening is performed manually or on straightening rolls, presses, sheet straightening and angle straightening machines, etc.

Straightening is done manually on a straightening cast iron plate or on a blacksmith's anvil using wood or metal hammers. Thin sheet material is straightened on correct slabs. When straightening sheet material less than 1 mm thick, wooden or steel bars are used to smooth the sheets onto the straightening plate. When straightening sheets more than 1 mm thick, wooden or metal hammers are used.

When manually editing sheet material, first, all bulges are identified and marked with chalk, then the sheet is laid on correct slab so that the bulges are on top. After this, they begin to strike with a hammer from one edge of the sheet in the direction of the convexity, and then from the other edge. The hammer blows should not be very strong, but frequent. The hammer should be held firmly and struck on the sheet central part striker, avoiding any distortions, since incorrect impacts may cause dents or other defects to appear on the sheet.

The strip material is straightened on straight slabs with hammer blows; Round bar material is straightened on a special straightening and calibrating machine.

Dents on the fenders, hood and body of the car are straightened first using shaped levers, then a blank or mandrel is installed under the dent and struck with metal or wooden hammer straighten out the dent.

Metal bending is used to obtain the required shape of products from sheet, rod, and pipe materials. Bending is carried out manually or mechanically.

When bending by hand, pre-marked a metal sheet installed in the device and clamped in a vice, after which the part protruding from the device is struck with a wooden hammer.

Pipes are bent manually or mechanically. Pipes large sizes(for example, a muffler pipe) is usually bent with preheating at the bending points. Small pipes (pipes for power and brake systems) are bent in a cold state. In order to prevent the walls of the pipe from being flattened during bending and the cross-section not to change at the bending points, the pipe is first filled with fine dry sand, rosin or lead. To obtain a normal rounding, and at the bend point the pipe is round (without folds or dents), you need to choose the bend radius correctly (a larger pipe diameter corresponds to a larger radius). For cold bending, pipes must first be annealed. The annealing temperature depends on the pipe material. For example, copper and brass pipes are annealed at a temperature of 600-700 °C followed by cooling in water, aluminum at a temperature of 400-580 °C followed by air cooling, steel at 850-900 °C followed by air cooling.

Rice. 43. Roller pipe bending device

Pipe bending is done using various devices. In Fig. 43 shows a roller device. Mechanical bending of pipes is carried out on pipe bending, edge bending machines, and universal bending presses.

Metal cutting

When cutting metal they use various instruments: wire cutters, scissors, hacksaws, pipe cutters. The use of a particular tool depends on the material, profile and size of the workpiece or part being processed. For example, to cut wire, wire cutters are used (Fig. 44a), which are made from tool steel grade U7 or U8. The cutting jaws are subjected to hardening followed by low (heating to 200° C and slow cooling) tempering.

Rice. 44. Tools for cutting metal: a - wire cutters, b - chair scissors, c - lever scissors

For cutting sheet material, hand, chair, lever, electric, pneumatic, guillotine, and disc shears are used. Thin sheet material (up to 3 mm) is usually cut with hand or chair scissors (Fig. 44, b), and thick (from 3 to 6 mm) with lever scissors (Fig. 44, c). Such scissors are made from carbon tool steel U8, U10. The cutting edges of the scissors are hardened. The sharpening angle of the cutting edges of scissors usually does not exceed 20-30°.

When cutting with scissors, a pre-marked metal sheet is placed between the blades of the scissors so that the marking line coincides with the upper blade of the scissors.

More and more wide application find electric and pneumatic shears. The body of the electric scissors contains an electric motor (Fig. 45), the rotor of which, using a worm gear, rotates an eccentric roller, to which a connecting rod is connected, driving the movable knife. The lower stationary knife is rigidly connected to the scissors body.

Rice. 45. Electric scissors I-31

Pneumatic shears operate under the influence of compressed air.

Mechanically driven guillotine shears cut steel sheets up to 40 mm thick. Disc shears cut sheet material up to 25 mm thick along straight or curved lines.

For cutting small workpieces or parts, hand and electromechanical hacksaws are used.

A hand saw (Fig. 46) is a steel sliding frame, called a machine, in which a steel hacksaw blade is secured. The hacksaw blade has the shape of a plate up to 300 mm long, 3 to 16 mm wide and 0.65 to 0.8 mm thick. The teeth of the hacksaw blade are set in different directions so that the width of the cut formed during cutting is 0.25-0.5 mm greater than the thickness of the hacksaw blade.

Hacksaw blades come with fine and large teeth. When cutting parts with thin walls, thin-walled pipes and thin rolled products, blades with fine teeth are used, and for cutting soft metals and cast iron - with large teeth.

The hacksaw blade is installed in the machine with the teeth forward and tensioned so that it does not warp during operation. Before starting work, the workpiece or part to be cut is installed and clamped in a vice so that the marking line (cut line) is located as close as possible to the jaws of the vice.

During operation, the mechanic should hold the hacksaw by the handle with his right hand, and his left hand should rest on the front end of the machine. When moving the hacksaw away from you, a working stroke is made. During this move, you need to apply pressure, and when moving the hacksaw back, i.e. when moving towards you, idling, in which pressure should not be applied.

Job hand hacksaw unproductive and tiring for the worker. The use of electromechanical hacksaws dramatically increases labor productivity. The structure of an electromechanical hacksaw is shown in Fig. 47. The hacksaw body contains an electric motor that rotates the shaft on which the drum is mounted.

Rice. 47. Electromechanical hacksaw

The drum has a spiral groove along which a finger fixed in the slide moves. A hacksaw blade is attached to the slide. When the electric motor operates, the drum rotates, and the hacksaw blade attached to the slide, performing a reciprocating motion, cuts the metal. The bar is designed to support the tool during operation.

Hacksaw blade.

Rice. 46. ​​Hacksaw:
1 - machine, 2 - fixed shackle, 3 - handle, 4 - hacksaw blade, 5 - magnifying glass, 6 - thumb, 7 - movable shackle

Rice. 48. Pipe cutter

A pipe cutter is used to cut pipes. It consists of a bracket (Fig. 48) with three disk cutters, of which the cutters are fixed and the cutter is movable, and a handle mounted on the thread. When working, put the pipe cutter on the pipe, turn the handle to move the movable disk until it comes into contact with the surface of the pipe, then, rotating the pipe cutter around the pipe, cut it.

Pipes and profile material They can also be cut with band saws or circular saws. The structure of the LS-80 band saw is shown in Fig. 49. On the saw bed there is a table with a slot designed for the passage (band) of the saw blade. At the bottom of the frame there is an electric motor and a driving pulley of the saw, and at the top of the frame there is a driven pulley. Using the handwheel, the saw blade is tensioned.

IN circular saws ah, instead of a cutting tape there is a cutting disk. A special feature of circular saws is the ability to cut profile metal at any angle.

For cutting hardened steel and hard alloys Thin grinding wheels are also used.

Metal filing

Filing is one of the types of metalworking, which consists in removing a layer of metal from a workpiece or part to obtain specified shapes, sizes and surface cleanliness.

This type of processing is performed with a special metalworking tool called a file. Files are made from tool steels U12, U12A, U13 or U13A, ShKh6, ShKh9, ShKh15 with mandatory hardening. According to the cross-sectional shape, files are divided into flat (Fig. 50, a), semicircular (Fig. 50.6), square (Fig. 50, c), triangular (Fig. 50, d), round (Fig. 50, e ) and etc.

According to the types of notches, files come with single and double notches (Fig. 51, a, b). Files with a single cut are used for filing soft metals (lead, aluminum, copper, babbitt, plastics), files with a double cut are used for processing hard metals. Depending on the number of notches per 1 linear line. cm, files are divided into six numbers. No. 1 includes coarsely cut files with a number of teeth from 5 to 12, the so-called “drachevye”. Files with a No. 2 cut have a number of teeth from 13 to 24, they are called “personal”. The so-called “velvet” files have a fine cut - No. 3, 4, 5, 6, and are manufactured with a number of teeth from 25 to 80.

Rice. 49. Band saw LS-80

Rice. 50. Files and their use (left):
a - flat, o - semicircular, c - square, d - triangular, d - round

For rough filing, when it is necessary to remove a layer of metal from 0.5 to 1 mm, bastard files are used, which can be used to remove a layer of metal 0.08-0.15 mm thick in one working stroke.

In cases where, after preliminary rough filing with brute files, clean and precise processing of the workpiece or part is required, personal files are used, which can be used to remove a layer of metal 0.02-0.03 mm thick in one stroke.

Rice. 51. File notch:
a - single, b - double

Velvet files are used for the most precise processing and giving the treated surface a high purity. For finishing and other special work, files called “needles” are used. They have the smallest notch. For filing soft materials (wood, leather, horn, etc.), files called rasps are used.

The choice of file depends on the hardness of the surface being processed and the shape of the workpiece or part. To increase the service life of files, it is necessary to take measures to prevent water, oil, and dirt from getting on them. After work, the file cut should be cleaned with a wire brush to remove dirt and sawdust stuck between the cut teeth. For storage, files are placed in tool boxes in one row, preventing them from touching each other. To prevent the file from becoming oily during operation, rub the notch with oil or dry charcoal.

Filing techniques. The productivity and accuracy of filing depend mainly on how coordinated the movements of the right and left hands are, as well as on the force of pressure on the file and the position of the mechanic's body. When filing, the mechanic stands on the side of the vice at a distance of approximately 200 mm from the edge of the workbench so that the movement of his hands is free. The position of the mechanic's body is straight and rotated 45° relative to the longitudinal axis of the vice.

The file is taken by the handle with the right hand so that thumb was located on top along the handle, and the remaining fingers clasped it from below. Left hand should rest with your palm across the top surface of the front end of the file.

The movement of the file must be strictly horizontal, and the force of hand pressure must be adjusted depending on the fulcrum of the file on the surface being processed. If the fulcrum is in the middle of the file, then the pressure with both hands should be the same. When moving the file forward, you need to increase the pressure of the right hand, and, on the contrary, decrease the pressure with the left. The file must move backward without pressure.

When filing, traces of file teeth, called streaks, remain on the surface being processed. The strokes, depending on the direction of movement of the file, can be longitudinal or cross. The quality of filing is determined by how evenly the strokes are spaced. To obtain a straight sawn surface, evenly covered with strokes, cross filing is used, which consists of first filing in parallel strokes from right to left, and then from left to right (Fig. 52,a).

After rough filing, check the quality of work against the light with a straight edge, which is applied along, across and diagonally to the processed plane. If the gap is the same or there is no gap at all, the quality of filing is considered good.

A more accurate method is the “paint” test, which consists of applying thin layer paint (usually blue or soot diluted in oil) and place the part on it with the treated surface, and then, lightly pressing on the part, move it across the entire slab and remove it. If traces of paint are evenly distributed over the entire surface of the part, it is considered that filing has been performed correctly.

Thin round parts are filed as follows. Clamped in a vice wooden block with a triangular cutout into which the part to be filed is placed, and its end is clamped in a hand vise (Fig. 52, b). When filing, the hand vise, together with the part fixed in it, is gradually turned with the left hand.

When filing several planes located at an angle of 90° relative to each other, proceed as follows. First, wide opposite planes are processed by cross-filing and checked for parallelism. After this, one of the narrow planes is filed with longitudinal strokes. The quality of its processing is checked with a ruler against the light, the angles formed with a wide plane are checked with a square. Then the remaining planes are filed. Narrow planes are checked for mutual perpendicularity with a square.

When filing parts made of thin sheet metal, wide planes are first processed on surface grinding machines, then the parts are combined into packs and their edges are filed using conventional techniques.

Sawing straight shaped armholes usually begins with the manufacture of liners and only after that do they begin to make armholes. First, the outer edges of the armhole are filed, then the center and contours of the armhole are marked, after marking, a round hole is drilled so that the edges of the hole are at least 1-2 mm away from the marking lines. After this, preliminary filing of the hole (armhole) is carried out and trimming is done in its corners with a needle file.

Rice. 52. Filing surfaces:
a - wide flat, b - cylindrical

Then they begin the final processing, first filing two mutually parallel sides of the armhole, after which the adjacent side is filed according to the template, and then the next opposite side, parallel to it. Mark the armhole a few hundredths of a millimeter smaller than the dimensions of the liner. When the armhole is ready, make a fitting (exact fit of the parts to each other) according to the liner.

After fitting, the liner should fit into the armhole and have no gaps in the places of contact with it.

Identical parts are made by filing using a master-conductor. The copier-conductor is a device, the contour of the working surfaces of which corresponds to the contour of the part being manufactured.

To file along a copier-conductor, the workpiece is clamped together with the copier in a vice (Fig. 53) and the parts of the workpiece protruding beyond the contour of the copier are filed. This processing method increases labor productivity when filing parts made of thin sheet material, which are clamped in a vice several at a time.

Mechanization of the filing process. At repair enterprises, manual filing is replaced by mechanized filing, performed in filing stations. machines using special devices, electric and pneumatic grinders. Lightweight portable machines include a very convenient electric Sander I-82 (Fig. 54, a) and pneumatic grinding machine ShR-06 (Fig. 54,6), on the spindle of which there is an abrasive wheel. The spindle is driven by a pneumatic rotary motor.

For filing surfaces in hard to reach places a mechanical file is used (Fig. 54, c), powered by an electric drive with a flexible shaft that rotates the tip /. The rotation of the tip is transmitted through the roller and worm gear to the eccentric 2. When the eccentric rotates, it imparts a reciprocating movement to the plunger 3 and the file attached to it.

Safety precautions when filing. The workpiece to be sawn must be securely clamped in a vice so that during operation it cannot change its position or jump out of the vice. Files must be with wooden handles, on which metal rings are mounted. The handles fit firmly onto the file shanks.

The shavings formed during filing are removed with a hair brush. It is strictly forbidden for a mechanic to remove chips with bare hands or blow it off, as this may cause injury to your hands and eyes.

Rice. 53. Filing according to the copier:
1 - copy bar, 2 - removable layer

Rice. 54. Tools for mechanized filing:
a - electric grinder I-82, 6 - pneumatic grinder ShR-06, c - mechanical file

When working with portable electric tools It is necessary to first check the reliability of their grounding.

Scraping

Scraping is the process of removing a very thin layer of metal from insufficiently flat surface a special tool - a scraper. Scraping is the final (precise) finishing of the surfaces of mating parts of machine tools, bearing shells, shafts, testing and marking plates, etc. to ensure a tight fit of the joint parts.

The scrapers are made from high-carbon tool steel U12A or U12. Often, scrapers are made from old files, removing the notch from them with an emery wheel. The cutting part of the scraper is hardened without subsequent tempering in order to give it high hardness.

The scraper is sharpened on an emery wheel so that the sharpening marks are located across the blade. To avoid excessive heating of the blade when sharpening, the scraper is periodically cooled in water. After sharpening, the scraper blade is polished on whetstones or on abrasive wheels, the surface of which is coated with machine oil.

Scrapers come with one or two cutting ends, the first are called one-sided, the second - double-sided. According to the shape of the cutting end, scrapers are divided into flat (Fig. 55, a), triangular (Fig. 55, b) and shaped.

Flat one-sided scrapers come with a straight or bent down end and are used for scraping flat surfaces of grooves and grooves. For scraping curved surfaces (when processing bushings, bearings, etc.), triangular scrapers are used.

Shaped scrapers are designed for scraping shaped surfaces, grooves, grooves, grooves, etc., with complex profiles. A shaped scraper is a set of steel plates, the shape of which corresponds to the shape of the surface being processed. The plates are mounted on a metal holder. scraper and secured to it with a nut.

The quality of surface treatment by scraping is checked on a surface plate.

Depending on the length and width of the flat surface being processed, the scraping allowance should be from 0.1 to 0.4 mm.

Before scraping, the surface of the part or workpiece is treated with metal cutting machines or filing.

After pre-treatment, scraping begins. The surface of the surface plate is covered with a thin layer of paint (red lead, blue or soot diluted in oil). The surface to be treated is thoroughly wiped with a rag, carefully placed on the surface plate and slowly moved along it in a circular motion, after which it is carefully removed.

As a result of this operation, all areas protruding on the surface are painted and clearly visible as spots. Painted areas (stains) along with the metal are removed with a scraper. Then the surface to be treated and the surface plate are cleaned and the plate is again coated with a layer of paint, and the workpiece or part is placed on it again.

Rice. 55. Hand scrapers:
a - straight flat one-sided and flat one-sided with a bent end, b - triangular

Newly formed stains on the surface are again removed with a scraper. During repeated operations, the spots will become smaller in size, and their number will increase. Scrape until the spots are evenly distributed over the entire surface to be treated, and their number meets the technical conditions.

When scraping curved surfaces (for example, a bearing shell), instead of a surface plate, use a shaft neck, which must be in contact with the surface of the shell being processed. In this case, the bearing shell is placed on the shaft journal, covered with a thin layer of paint, carefully rotated around it, then removed, clamped in a vice and scraped over the spots.

When scraping, the scraper is installed in relation to the surface being processed at an angle of 25-30° and held with the right hand by the handle, pressing the elbow to the body, and pressed on the scraper with the left hand. Scraping is carried out with short movements of the scraper, and if the scraper is flat and straight, then its movement should be directed forward (away from you), with a flat scraper with the end bent downwards the movement is made back (toward you), and with a triangular scraper - to the side.

At the end of each stroke (movement) of the scraper, it is torn off from the surface being processed so that burrs and ledges do not form. To obtain a smooth and precise surface to be processed, the direction of scraping is changed each time after checking the paint so that the strokes intersect.

The accuracy of scraping is determined by the number of evenly spaced spots on an area measuring 25X25 mm2 of the treated surface by placing a control frame on it. The average number of stains is determined by checking several areas of the surface being treated.

Manual scraping is very labor-intensive and therefore in large enterprises it is replaced by grinding, turning, or it is carried out by mechanized scrapers, the use of which facilitates labor and dramatically increases its productivity.

Rice. 56. Mechanized scraper

The mechanized scraper is driven by an electric motor (Fig. 56) through a flexible shaft connected at one end to the gearbox and the other to the crank. When the electric motor is turned on, the crank begins to rotate, imparting a reciprocating motion to the connecting rod and the scraper attached to it. In addition to the electric scraper, pneumatic scrapers are used.

Lapping

Lapping is one of the most accurate methods final finishing processed surface, providing high processing accuracy - up to 0.001-0.002 mm. The grinding process involves removing the thinnest layers of metal using abrasive powders and special pastes. For lapping, abrasive powders from corundum, electrocorundum, silicon carbide, boron carbide, etc. are used. Lapping powders are divided into grinding powders and micropowders based on their grain size. The former are used for rough grinding, the latter for preliminary and final finishing.

For grinding the surfaces of mating parts, for example, valves to seats in engines, nipples to valve sockets, etc., GOI (State Optical Institute) pastes are mainly used. GOI pastes can be used to grind any metals, both hard and soft. These pastes are available in three types: coarse, medium and fine.

Coarse GOI paste is dark green (almost black), medium is dark green, and fine is light green. Lapping tools are made of gray fine-grained cast iron, copper, bronze, brass, and lead. The shape of the lap must match the shape of the surface being ground.

Lapping can be carried out in two ways: with and without lapping. Processing of non-mating surfaces, such as gauges, templates, squares, tiles, etc., is carried out using a lap. The mating surfaces are usually ground to each other without the use of a lap.

Lappings are movable rotating disks, rings, rods or fixed plates.

The grinding process of non-mating planes is carried out as follows. A thin layer of abrasive powder or paste is applied to the surface of the flat lap, which is then pressed into the surface with a steel bar or rolling roller.

When preparing the lapping cylindrical The abrasive powder is poured into an even thin layer onto a hardened steel plate, after which the lap is rolled along the surface until the abrasive powder is pressed into its surface. The prepared lap is inserted into the workpiece and, with light pressure, is moved along its surface or, conversely, the workpiece is moved along the surface of the lap. Abrasive grains of powder, pressed into the lap, cut off a layer of metal 0.001-0.002 mm thick from the surface of the part being ground.

The workpiece must have a lapping allowance of no more than 0.01-0.02 mm. To improve the quality of grinding, lubricants are used: machine oil, gasoline, kerosene, etc.

The mating parts are lapped without lapping. A thin layer of the appropriate paste is applied to the surfaces of the parts prepared for grinding, after which the parts begin to move one over the other in a circular motion, first in one direction, then in the other.

The manual grinding process is often replaced by a mechanized one.

Automotive repair shops use rotators, electric drills and pneumatic machines to grind valves into seats.

The valve is ground to its seat as follows. The valve is installed in the guide sleeve of the cylinder block, having previously placed a weak spring and a felt ring on the valve stem, which protects the guide sleeve from getting lapping paste into it. After this, the working chamfer of the valve is lubricated with GOI paste and they begin to rotate the valve with a hand or electric drill, making one third of a turn to the left, and then two or three turns to the right. When changing the direction of rotation, it is necessary to loosen the pressure on the drill so that the valve, under the action of a spring placed on its rod, rises above the seat.

The valve is usually rubbed in first with a coarse paste, and then with a medium and fine paste. When a matte gray stripe in the form of a ring without spots is formed on the working chamfer of the valve and seat, the grinding is considered complete. After lapping, the valve and seat are thoroughly washed to remove any remaining particles of lapping paste.

Drilling is used to obtain workpieces or parts round holes. Drilling is carried out on drilling machines or a mechanical (manual), electric or pneumatic drill. The cutting tool is a drill. Drills according to their design are divided into feather, spiral, center, drills for drilling deep holes and combined. IN plumbing Spiral drills are mainly used. Drills are made from tool carbon steels U10A, U12A, as well as from alloy chromium steels 9ХС, 9Х and high-speed cutting steels Р9 and Р18.

A twist drill (Fig. 57) has the shape of a cylindrical rod with a cone-shaped working end, which has two helical grooves on the sides with an inclination to the longitudinal axis of the drill of 25-30°. These grooves carry the chips out. The tail part of the drill is made cylindrical or conical. The sharpening angle at the tip of the drill can be different and depends on the material being processed. For example, for processing soft materials it should be from 80 to 90°, for steel and cast iron 116-118°, for very hard metals 130-140°.

Drilling machines. In repair shops, single-spindle vertical drilling machines are most commonly used (Fig. 58). The workpiece or part to be processed is placed on a table that can be raised and lowered using a screw. The handle secures the table to the frame at the required height. The drill is installed and secured in the spindle. The spindle is driven by an electric motor through a gearbox, and automatic feeding is carried out by a feedbox. Vertical movement of the spindle is carried out manually using a flywheel.

A hand drill (Fig. 59) consists of a spindle on which the chuck is located, a bevel gear (consisting of a large and small gear wheels), fixed handle, movable handle and bib. The drill is inserted into the chuck and secured. When drilling, the mechanic holds the drill with his left hand by the fixed handle, and with his right hand he rotates the movable handle, leaning his chest on the breastplate.

Rice. 57. Twist drill:
1 - working part of the drill, 2 - neck, 3 - shank, 4 - foot, l - groove, 6 - feather, 7 - guide chamfer (ribbon), 8 - rear sharpening surface, 9 - cutting edges, 10 - jumper, 11 - cutting part

Rice. 58. Single-spindle vertical drilling machine 2135

A pneumatic drill (Fig. 60, a) operates under the influence of compressed air. It is convenient to use, as it is small in size and weight.

An electric drill (Fig. 60, b) consists of an electric motor, a gear and a spindle. A chuck is screwed onto the end of the spindle, in which the drill is clamped. There are handles on the casing, and in the upper part of the body there is a breastplate for support when working.

Drilling is done either according to the markings or according to the jig. When drilling according to markings, first mark the hole, then mark it around the circumference and in the center. After this, secure the workpiece in a vice or other device and begin drilling. Drilling along the markings is usually carried out in two steps. First, drill a hole to a depth of a quarter of the diameter. If the resulting hole (not through) coincides with the marked one, then continue drilling, otherwise correct the installation of the drill and only then continue drilling. This method is most widely used.

Rice. 59. Hand drill

Rice. 60. Pneumatic (a) and electric (b) drills:
1 - rotor, 2 - stator, 3 - chuck, 4 - spindle, 5 - gearbox, 6 - trigger

Drilling large quantity identical parts with high accuracy is carried out using a jig (a template with precisely made holes). The jig is placed on the workpiece or part being processed and drilling is carried out through the holes in the jig. The jig does not allow the drill to deviate, so the holes are accurate and located at the required distance. When drilling a hole for a thread, it is necessary to use reference manuals to select the drill diameter in accordance with the type of thread, as well as taking into account the mechanical properties of the material being processed.

Causes of drill bit failures. The main causes of drill breakages during drilling are: deviation of the drill to the side, the presence of shells in the workpiece or part being processed, clogging of the grooves on the drill with chips, improper sharpening of the drill, poor heat treatment of the drill, dull drill.

Sharpening drills. On work productivity and drilling quality big influence sharpening of the drill. Drills are sharpened on special machines. In small workshops, drills are sharpened by hand using emery sharpeners. Control of drill sharpening is carried out with a special template having three surfaces a, b, c (Fig. 61).

Countersinking of holes is the subsequent (after drilling) processing of holes, which consists of removing burrs, chamfering and obtaining a conical or cylindrical recess at the entrance part of the hole. Countersinking is carried out with special cutting tools - countersinks. According to the shape of the cutting part, countersinks are divided into cylindrical and conical (Fig. 62, a, b). Conical countersinks are used to produce conical recesses in holes for the heads of rivets, countersunk screws and bolts. Conical countersinks can be with apex angles of 30, 60 and 120°.

Cylindrical countersinks are used to process the planes of the bosses, the recesses for the heads of screws, bolts, screws, and washers. A cylindrical countersink has a guide pin that fits into the hole being machined and provides right direction countersinks. Countersinks are made from carbon tool steels U10, U11, U12.

Countersinking is the subsequent processing of holes before deployment with a special tool - a countersink, the cutting part of which has more cutting edges than a drill.

According to the shape of the cutting part, countersinks are spiral and straight; according to their design, they are divided into solid, mounted and with inserted knives (Fig. 63, a, b, c). Depending on the number of cutting edges, countersinks come in three- and four-tooth types. Solid countersinks have three or four cutting edges, mounted - four cutting edges. Countersinking is performed on drilling machines, as well as pneumatic and electric drills. Countersinks are attached in the same way as drills.

Reaming is the finishing of a hole performed with a special cutting tool called a reamer.

When drilling a hole, leave an allowance for the diameter for rough reaming of no more than 0.2-0.3 mm, and for finishing reaming - 0.05-0.1 mm. After deployment, the hole size accuracy increases to class 2-3.

Rice. 61. Template for controlling drill sharpening

Rice. 62. Countersinks:
a - cylindrical, b - conical

According to the method of actuation, reamers are divided into machine and manual, according to the shape of the hole being machined - into cylindrical and conical, according to their design - into solid and prefabricated. Reamers are made from tool steels.

Cylindrical solid reamers come with straight or helical (spiral) teeth, and therefore the same grooves. Cylindrical reamers with a spiral tooth can have right or left grooves (Fig. 64, a, b). The reamer consists of a working part, a neck and a shank (Fig. 64, c).

Rice. 63. Countersinks:
a - solid, b - mounted, i - with insert knives

Rice. 64. Cylindrical reamers:
a - with a right helical groove, b - with a left helical groove, c - the main parts of the reamer

The cutting, or intake, part is made conical; it performs the main cutting work of removing the allowance. Each cutting edge forms a main angle in plan with the reamer axis Ф (Fig. 64, c), which for manual reamers is usually 0.5-1.5°, and for machine reamers 3-5° - for processing hard metals and 12- 15° - for processing soft and tough metals. .

The cutting edges of the fence part form an angle with the axis of the reversal at the apex of 2 cf. The end of the cutting part is chamfered at an angle of 45°. This is necessary to protect the tops of the cutting edges from nicks and chipping during operation.

The calibrating part of the reamer produces almost no cutting; it consists of two sections: a cylindrical section, which serves to calibrate the hole, the direction of the reamer, and a section with a reverse taper, designed to reduce the friction of the reamer on the surface of the hole and protect the hole from development.

The neck is the section of the reamer between the working part and the shank. The diameter of the neck is 0.5-1 mm less than the diameter of the calibrating part. Machine reamers have conical shanks, while hand reamers have square shanks. Reamers come with uniform and uneven tooth pitch. Machine reamers are secured in the machine spindle using conical sleeves and chucks, manual reamers- in the crank, with the help of which deployment is carried out.

Conical reamers used for deployment conical holes for Morse taper, for metric taper, for pins with a taper of 1:50. Conical reamers are made in sets of two or three pieces. A set of three scans consists of a rough, intermediate and finishing (Fig. 65, a, b, c). In a set of two reamers, one is transitional and the other is finishing. Conical reamers are made with a cutting part along the entire length of the tooth, which for finishing reamers is also a calibrating part.

Deployment by hand and on machines. Manual deployment is carried out using a crank in which the reamer is secured. When manually unfolding, small workpieces or parts are secured in a vice, while large ones are processed without securing.

After securing the workpiece or part, the cutting part of the reamer is inserted into the hole so that the axes of the reamer and the hole coincide. After this, slowly rotate the reamer clockwise; You cannot rotate the reamer in the opposite direction, as scoring may occur. When machine reaming on machines proceed in the same way as when drilling.

Rice. 65. Conical reamers:
a - rough, b - intermediate, c - finishing

When drilling holes in steel workpieces or parts, mineral oils are used as a lubricant; in copper, aluminum, brass parts - soap emulsion. In cast iron and bronze workpieces, holes are drilled dry.

The choice of reamer diameter has great importance to obtain the required hole size and surface cleanliness. In this case, the thickness of the chips removed by the tool is taken into account (Table 2).

Using this table, you can select the diameter of the reamer and countersink.

Example. It is necessary to manually unroll a hole with a diameter of 50 mm. To do this, take a finishing reamer with a diameter of 50 mm, and a rough reamer 50-0.07 = 49.93 mm.

When choosing a machine finishing ream, you should take into account the amount of development, i.e., the increase in the diameter of the hole during machine reaming.

When processing holes with a drill, countersink and reamer, the following basic safety rules must be observed:

perform work only on working machines that have the necessary guards;

Before starting work, put your clothes and hats in order. When working, clothing should fit the body without fluttering hems, sleeves, belts, ribbons, etc., it should be tightly buttoned.

Long hair should be matched to a headdress:
– a drill, countersink, reamer or fixture is accurately installed in the machine spindle and firmly secured;
– it is strictly prohibited to remove chips from the resulting hole with your fingers or blow them away. It is allowed to remove chips only with a hook or brush after stopping the machine or when retracting the drill;
– the workpiece or part being processed must be installed motionless on the table or plate of the machine in a fixture; you cannot hold it with your hands during processing;
– do not install the tool while the spindle is rotating or check the sharpness of the rotating drill with your hand;
– when working with an electric drill, its body must be grounded, the worker must be on an insulated floor.

Threading

Threading is the process of producing helical grooves on cylindrical and conical surfaces. The set of turns located along a helical line on a product is called a thread.

Threads can be external or internal. The main elements of any thread are profile, pitch, height, outer, middle and inner diameters.

Rice. 66. Thread elements

The thread profile is the cross-sectional shape of a thread passing through the axis of a bolt or nut (Fig. 66). A thread (turn) is the part of the thread formed during one full revolution of the profile.

The thread pitch is the distance between two points of the same name on adjacent threads, measured parallel to the axis of the thread, the axis of the bolt or nut.

Thread height is defined as the distance from the top of the thread to the base.

The top of the thread is the section of the thread profile located on greatest distance from the thread axis (bolt or nut axis).

The base of the thread (the root) is the section of the thread profile located at the shortest distance from the thread axis.

The thread profile angle is the angle between the two flanks of the thread profile.

Outer thread diameter - largest diameter, measured at the top of the thread in a plane perpendicular to the axis of the thread.

Rice. 67. Thread systems:
a - metric; b - inch, c - pipe

The average thread diameter is the distance between two lines parallel to the axis of the bolt, each of which is at a different distance from the top of the thread and the bottom of the gullet. The width of the external and internal threads, measured along the circle of the average diameter, is the same.

The internal diameter of a thread is the smallest distance between opposite thread roots, measured in a direction perpendicular to the thread axis.

Profiles and thread systems. Various thread profiles are used in machine parts. The most common are triangular, trapezoidal and rectangular profiles. According to their purpose, threads are divided into fastening and special. Triangular threads are used to fasten parts together (threads on bolts, studs, nuts, etc.); they are often called fastening threads. Trapezoidal and rectangular threads are used on parts of motion transmission mechanisms (screws of metalworking disks, lead screws of screw-cutting lathes, lifts, jacks, etc.). R. There are three thread systems: metric, imperial and pipe. The main one is a metric thread, which has a profile in the form of an equilateral triangle with an apex angle of 60° (Fig. 67, a). To avoid jamming during assembly, the tops of the threads of the bolts and nuts are cut off. Metric thread sizes are given in millimeters.

Pipe thread is a fine inch thread. It has the same profile as the inch one, with an apex angle of 55° (Fig. 67, c). Pipe threads are used mainly for gas and water pipes and couplings connecting these pipes.

Tools for cutting external threads. For slicing external thread a die is used, which is a split or split ring with a thread on inner surface(Fig. 68, a, b). The chip flutes of the die serve to form cutting edges and also to release chips.

Based on their design, dies are divided into round dies, sliding dies, and special dies for cutting pipes. Round dies are either solid or split. Solid round dies have great rigidity and ensure clean threads. Split dies are used for cutting low-precision threads.

Sliding dies consist of two halves, which are called half-dies. On the outer sides of the half-dies there are grooves with an angle of 120° for securing the half-dies in the die. Each half-die is marked with a thread diameter and numbers 1 and 2, which are used as a guide when installing them in the die. Dies are made of tool steel U£2"

Manual thread cutting with dies is carried out using cranks and clamps. When working with round dies, special wrenches are used (Fig. 68, c). The frame of such a shortcut has the shape of a round die. A round die is installed in the frame hole and secured with three locking screws having conical ends that fit into special recesses on the die. The fourth screw, included in the section of the adjustable die, sets the outer thread size.

Rice. 68. Tools for cutting external threads:
a - split die, b - sliding die, c - knob, d d - die with an oblique frame

Sliding dies are installed in a die with an oblique frame (Fig. 68, d), which has two handles. Both half-dies are installed in the frame. Using an adjusting screw, the half-dies are brought together and installed to obtain the thread of the desired size. A cracker is inserted between the outer half-die and the adjusting screw, ensuring uniform distribution of screw pressure on the half-dies.

Threads are cut by hand and on machines. In plumbing they are more often used hand tools. Cutting external threads with sliding dies is as follows. The blank of a bolt or other part is clamped in a vice and lubricated with oil. Then a die with dies is placed on the end of the workpiece and the dies are brought together with an adjusting screw so that they cut into the workpiece by 0.2-0.5 mm.

After this, they begin to rotate the die, turning it 1-2 turns to the right, then half a turn to the left, etc. This is done until the thread is cut to the required length of the part.

Then the die is rolled along the thread to its original position, the dies are brought closer together with the adjusting screw and the cutting process is repeated until a complete thread profile is obtained. After each pass, it is necessary to lubricate the part of the workpiece being cut. Thread cutting with solid dies is done in one pass.

Rice. 69. Bench taps:
a - main parts of the tap, b - set of taps: 1 - rough, 2 - medium, 3 - finishing

Tools for cutting internal threads. Internal thread cut with a tap both on machines and by hand. In plumbing, they mainly use the manual method.

The tap (Fig. 69, a) is a steel screw with longitudinal and helical grooves that form cutting edges. The tap consists of a working part and a shank. The working part is divided into intake and calibrating parts.

The cutting part of the tap is the front conical part, which performs the main cutting work. The calibration part serves to guide the tap in the hole when cutting and calibrating threads. The teeth of the threaded part of the tap are called cutting feathers. The shank is used to secure the tap in the chuck or in the driver. The shank ends in a square. According to their purpose, taps are divided into metalworking taps, nut taps, machine taps, etc.

Taps are used for cutting threads by hand; they are produced in sets of two or three pieces. Set of taps”“’ for cutting metric and inch threads consists of three pieces: rough, medium and finishing (Fig. 69, b). The intake part of the rough tap has 6-8 turns, the middle tap has 3-4 turns, and the finishing part has 1.5-2 turns. A rough tap is used to make preliminary cuts, a medium tap is used to make the thread more accurate, and a finishing tap is used to make the final cutting and calibrate the thread.

According to the design of the cutting part, taps are cylindrical and conical. With a cylindrical design, all three taps in the set have different diameters. Only the finishing tap has a full thread profile, outside diameter the average tap is smaller than the finishing tap by 0.6 of the thread height, and the diameter of the rough tap is smaller than the finishing tap by the full thread height. Taps with a cylindrical cutting part are used mainly for cutting threads in blind holes.

With a tapered design, all three taps have the same diameter, full thread profile with different lengths of intake parts. These taps are used for cutting threads in through holes. Taps are made from tool carbon steels U10, U12. Threads are cut manually using a crank having a square hole.

The workpiece or part is secured in a vice, and the tap is secured in the driver. The thread cutting process is as follows. The roughing tap is installed vertically in the prepared hole and, using a wrench, begins to rotate it clockwise with light pressure. After the tap hits the metal, the pressure is stopped and rotation continues.

Periodically you need to check the position of the tap with a square in relation to the upper plane of the workpiece. The tap should be turned 1-2 turns clockwise, and then half a turn counterclockwise. This should be done for

so that the chips resulting from cutting are crushed and thereby make the work easier.

After the rough tap, cutting is done with a medium tap and then a fine tap. To obtain a clean thread and cool the tap during cutting, a lubricant is used. When cutting threads in steel workpieces, mineral oil, drying oil or emulsion are used as lubricants and coolants, in aluminum - kerosene, in copper - turpentine. In cast iron and bronze workpieces, threads are cut dry.

When cutting threads in workpieces made of soft and tough metals (babbitt, copper, aluminum), the tap is periodically unscrewed from the hole and the grooves are cleared of chips.

When working with a tap, various defects are possible, for example, breakage of the tap, torn threads, stripped threads, etc. The causes of these defects are: a dull tap, clogging of the tap grooves with chips, insufficient lubrication, incorrect installation of the tap in the hole and selection of the hole diameter, as well as inattentive attitude of the worker .

Riveting

When repairing machines and assembling them, a mechanic has to deal with various connections details. Depending on the assembly method, connections can be detachable or permanent. One of the ways to assemble parts into a permanent connection is riveting.

Riveting is done using rivets either manually or by machine. Riveting can be cold or hot.

The rivet is a cylindrical rod with a head at the end, which is called a rivet. In the process of riveting the rod, a second head is formed, called the closing head.

Rice. 70. Main types of rivets and rivet seams:
heads: a - semicircular, 6 - countersunk, c - semi-countersunk, d - pitch of the rivet connection; seams; d - overlap, e - butt with one overlay, g - butt with two overlays

According to the shape of the embedded head, rivets come with a semicircular head, with a semi-countersunk head, with a countersunk head (Fig. 70, a, b, c), etc.

The connection of parts made with rivets is called a rivet seam.

Depending on the location of the rivets in the seam in one, two or more rows, rivet seams are divided into single-row, double-row, and multi-row.

The distance t between the centers of rivets of one row is called the pitch of the rivet connection (Fig. 70, d). For single-row seams, the pitch should be equal to three rivet diameters, the distance a from the center of the rivet to the edge of the riveted parts should be equal to 1.5 rivet diameters at drilled holes and 2.5 diameters with punched holes. In double-row seams, the pitch is taken equal to four rivet diameters, the distance from the center of the rivets to the edge of the parts being riveted is 1.5 diameters, and the distance between the rows of rivets should be equal to two rivet diameters.

Riveted joints are made in three main ways: lap, butt with one overlay and butt with two overlays (Fig. 70, e, f, g). According to their purpose, rivet seams are divided into strong, dense and strong-dense.

The quality of a rivet seam largely depends on whether the rivet is selected correctly.

Equipment and tools used for manual and mechanized riveting. Manual riveting is carried out using a mechanic's hammer with a square striker, support, tension and crimping (Fig. 71). Hammers come in weights from 150 to 1000 g. The weight of the hammer is selected in accordance with the diameter of the rivet rod,

The support serves as a support for the closing head of the rivet when riveting, the tension serves to bring the parts to be riveted closer together, and crimping is used to give the correct shape to the closing head of the rivet.

Mechanized riveting is carried out using pneumatic structures. The pneumatic riveting hammer (Fig. 72) operates under the influence of compressed air and is activated by a trigger. When you press the trigger, valve 9 opens and compressed air, entering through the channels into the left side of the barrel chamber, actuates the firing pin, which strikes the crimp.

Rice. 71. Auxiliary Tools used for riveting:
1 - crimping, 2 - support, 3 - tension

After the impact, the spool shuts off the flow of air into channel 3, connecting it to the atmosphere, and the compressed air is directed through channel 4 to the right side of the barrel chamber, while the striker is thrown away; channel 4 is blocked from action, etc. The pneumatic work is performed by two people , one does the riveting with a hammer, and the other is a helper.

Rice. 72. Pneumatic riveting hammer P-72

The riveting process is as follows. A rivet is inserted into the hole and installed with the mounting head on a support clamped in a vice. After this, a tension is installed on the rivet rod. The head of the tensioner is hit with a hammer, causing the parts to be riveted together to be brought together.

Then they begin to rivet the rivet rod with hammer blows, alternately delivering straight and oblique blows directly to the rod. As a result of riveting, a closing rivet head is obtained. To give the closing head the correct shape, a crimp is put on it and the final processing of the head is carried out by hitting the crimp with a hammer, giving it the correct shape.

For rivets with a countersunk head, the hole is pre-processed with a countersink to a cone. Rivet the countersunk head with straight hammer blows directed exactly along the rivet axis.

The most common riveting defects are the following: bending of the rivet rod in the hole, resulting from the fact that the diameter of the hole was very large; deflection of the material due to the fact that the hole diameter was small; displacement of the rivet head (the hole was drilled obliquely), bending of the closure head resulting from the fact that the rivet rod was very long or the support was not installed along the rivet axis; undercutting of a part (sheet) due to the fact that the crimp hole was larger than the rivet head, cracks on the rivet heads that appear when the rivet material is insufficiently ductile.

Safety precautions. When performing riveting work, the following safety rules must be observed: the hammer must be securely mounted on the handle; the hammer heads and crimps should not have potholes or cracks, since they can split during the riveting process and injure both the worker doing the riveting and the workers nearby with fragments; When using a pneumatic hammer, it must be adjusted. When adjusting, you should not try the hammer while holding the crimp with your hands, as this can lead to serious injury to your hand.

Pressing in and pressing out

When assembling and disassembling assemblies consisting of fixed parts, pressing and unpressing operations are used, carried out using presses and special pullers.

Pressing out is often done using screw pullers. A puller for pressing out bushings is shown in Fig. 73. It has a gripper which is pivotally connected to the end of the screw. To secure the pressed-out bushing in it, the gripper is tilted and inserted into the bushing.

Rice. 73. Puller for pressing out bushings

Pullers can be special or universal. Universal pullers can be used to press out parts of various shapes.

In auto repair shops, when disassembling and assembling cars, presses are used for pressing in and out. various designs: hydraulic (Fig. 74), rack bench, screw bench (Fig. 75, a, b). Bench bench rack and bench screw machines are used for pressing out bushings, pins and other small parts. The pressing and pressing of large parts is carried out using hydraulic presses.

When pressing in and out hydraulic press proceed as follows. First of all, by rotating the handle (see Fig. 74), the lifting table is installed so that the part being pressed in or pressed out freely passes under the rod, and it is secured with studs.

Rotating the flywheel, lower the rod until it stops with the part. After this, a lever is used to activate the pump, which pumps oil from the tank into the press cylinder. Under oil pressure, the piston and the rod connected to it are lowered. While moving, the rod presses (or presses out) the part. After the work is completed, the valve is opened and the piston springs upward along with the rod. The oil from the cylinder is transferred back to the reservoir.

Rice. 74. Hydraulic press:
1 - lifting table, 2 - table lifting handle, 3 - rollers for winding the cable, 4 - lifting spring, 5 - pressure gauge, 6 - cylinder, 7 - release valve, 8 - pump lever, 9 - oil tank, 10 - rod , 11 - flywheel, 12 - pressed part, 13 - bed

Rice. 75. Mechanical presses:
a - rack bench, 6 - screw bench

In all cases of pressing, to protect the surface of parts from damage and jamming, they are first cleaned of rust, scale and lubricated with oil. There should be no nicks, scratches or burrs on parts prepared for pressing.

Soldering

Soldering is a connection method metal parts with each other using special alloys called solders. The soldering process consists of placing the parts to be soldered one next to the other, heating them to a temperature slightly higher than the melting point of the solder, and liquid molten solder is introduced between them.

To obtain a high-quality solder joint, the surfaces of the parts are cleaned of oxides, grease and dirt immediately before soldering, since the molten solder does not wet contaminated areas and does not spread over them. Cleaning is carried out mechanically and chemically.

The surfaces to be soldered are first subjected to mechanical cleaning from dirt, rust with a file or scraper, then degrease them by washing them in a 10% solution of caustic soda or in acetone, gasoline, denatured alcohol.

After degreasing, the parts are washed in a bath with running water and then subjected to etching. Brass parts are etched in a bath containing 10% sulfuric acid and 5% chromium; for etching steel parts, a 5-7% solution is used of hydrochloric acid. At a solution temperature of no more than 40°C, parts d are kept in it for 20 to 60 minutes. ~~ At the end of etching, the parts are thoroughly washed, first in cold, then in hot water.

Before soldering, the working part of the soldering iron is cleaned with a file and then tinned (coated with a layer of tin).

When soldering, tin-lead and copper-zinc are most commonly used. copper, silver and copper-phosphorus solders.

To eliminate the harmful effects of oxides, fluxes are used, which fuse and remove oxides from the surfaces being soldered and protect them from oxidation during the soldering process. The flux is selected in accordance with the properties of the metals being soldered and the solders used.

Solders are divided into soft and hard. Soft solders are used to solder steel and copper alloys. Steel parts are tinned before soldering with soft solders. Only under this condition can a reliable solder connection be ensured.

The most common soft solders are tin-lead alloys of the following grades: POS-EO, POS-40, POS-ZO, POS-18. Solders are available in the form of rods, wires, strips and tubes. Zinc chloride, ammonium chloride (ammonia), rosin (for soldering copper and its alloys), 10% are used as fluxes when soldering with soft solders. water solution hydrochloric acid (for soldering zinc and galvanized products), stearin (for soldering low-melting lead alloys).

For soldering critical parts made of cast iron, steel, copper alloys, aluminum and its alloys, hard solders are used, mainly copper-zinc and silver of the following grades: PMC-36, PMC-48, PMC-54, PSr12, PSr25, PSr45 (melting temperature of hard alloys from 720 to 880 °C).

For soldering aluminum and its alloys, for example, solder of the following composition is used: 17% tin, 23% zinc and 60% aluminum. Borax is used as fluxes, boric acid and mixtures thereof. When soldering aluminum, they use a flux consisting of a 30% solution of an alcohol mixture, which contains 90% zinc chloride, 2% sodium fluoride, 8% aluminum chloride.

When soldering with hard solders, the parts are fixed in special devices in such a way that the gap between the parts does not exceed 0.3 mm. Then flux and solder are applied to the area to be soldered, and the part is heated to a temperature slightly above the melting point of the solder. The melted solder fills the gap and forms a strong connection as it cools.

After soldering is completed, the parts are cleaned of flux residues, since remaining fluxes can cause corrosion of the weld surface. The seams are cleaned with a file or scraper.

The main tools for soldering are soldering irons and blowtorches. In addition, when soldering, settings are used induction heating currents high frequency and other devices. When soldering with soft solders, soldering irons (Fig. 76, a, b, c) and blowtorches are usually used.

A hand-held soldering iron is made of copper and can have different shapes (Fig. 76, a, b). When brazing, the parts to be soldered are heated with a blowtorch or in a forge.

TO Category: - Car maintenance

Marking is the operation of applying marking marks to the surface of a part or workpiece to be processed, defining the contours of the part profile and the places to be processed. The main purpose of marking is to indicate the boundaries to which the workpiece must be processed. To save time, simple workpieces are often processed without preliminary marking. Blanks are received for processing in the form of castings (obtained from metal poured into pre-prepared molds - earthen, metal, etc.), forgings (obtained by forging or stamping), or in the form of rolled material - sheets, rods, etc. (obtained by passing metal between rollers rotating in different directions, having a profile corresponding to the resulting rolled product).

During processing, a certain layer of metal (allowance) is removed from the surface of the workpiece, as a result of which its size and weight are reduced. When manufacturing a part, its dimensions are laid down on the workpiece exactly according to the drawing and marked with lines (marks) indicating the processing boundaries to which the metal layer should be removed.

Marking is used mainly in single and small-scale production. Three main groups of markings are used: mechanical engineering, boiler room and ship. Mechanical marking is the most common metalworking operation. Planar marking is the application of various lines to the surfaces of flat workpieces on sheet and strip metal, as well as on the surfaces of cast and forged parts.

At spatial markings marking lines are applied in several planes or on several surfaces.

Apply various ways markings: according to drawing, template, sample and location. The choice of marking method is determined by the shape of the workpiece, the required accuracy and the number of products. The accuracy of marking significantly affects the quality of processing. The degree of marking accuracy ranges from 0.25 to 0.5 mm.

Errors made during marking lead to defects.

TO technical requirements Marking concerns, first of all, the quality of its execution, on which the accuracy of the manufacture of parts largely depends.

The marking must meet the following basic requirements: 1) exactly match the dimensions indicated on the drawing; 2) marking lines (marks) must be clearly visible and not erased during processing of the part; 3) do not spoil the appearance and quality of the part, i.e. the depth of the marks and core recesses must meet the technical requirements for the part.

When marking workpieces you must:

1. Carefully inspect the workpiece, when

If shells, bubbles, cracks, etc. are detected, they should be accurately measured and removed during further processing.

2. Study the drawing of the part to be marked, find out the features and dimensions of the part, its purpose; mentally outline the marking plan (installation of the part on the slab, method and order of marking, etc.). Special attention should be paid to allowances. Allowance for processing, depending on the material and size of the part, its shape, and method of installation during processing, is taken from the relevant reference books. All dimensions of the workpiece must be carefully calculated so that after processing there are no defects left on the surface.

3. Determine the surfaces (bases) of the workpiece from which dimensions should be taken during the marking process. For planar marking, the bases can be the processed edges of the workpiece or the center lines, which are applied first. It is convenient to take tides, bosses, and platikil as bases.

4. Prepare surfaces for painting.

For painting, i.e. covering surfaces before marking, use various compositions, in this case, a solution of susnendil chalk with the addition of glue is most often used. To prepare sus-netsdil, take 1 kg of chalk per 8 liters of water and bring to a boil. Then liquid wood glue is added to it again at the rate of 50 g per 1 kg of chalk. After adding glue, the composition is boiled again. To avoid damage to the composition (especially in summer time) it is recommended to add a small amount of linseed oil and drier to the solution. This paint is used to cover untreated workpieces. Painting is done with paint brushes, but this method is not very productive. Therefore, whenever possible, painting should be done using sprayers, which, in addition to speeding up the work, provide uniform and durable painting.

Dry chalk. When rubbing the surface to be marked with dry chalk, the color becomes less durable. This method is used to paint the untreated surfaces of small non-critical workpieces.

Copper sulfate solution. Three teaspoons of vitriol are dissolved in a glass of water. The surface, cleared of dust, dirt and oil, is covered with a vitriol solution with a brush. A thin layer of copper is deposited on the surface of the workpiece, on which marking marks are well applied. This method is used to paint only steel and cast iron workpieces with surfaces pre-treated for marking.

Alcohol varnish. Fuchsin is added to a solution of shellac in alcohol. This painting method is used only for precise marking of treated surfaces on large parts and products.

Quick-drying varnishes and paints are used to coat the surfaces of large machined steel and cast iron castings. Non-ferrous metals, hot-rolled sheet and profile steel are not painted with varnishes or paints.