Typical plumbing operations. Types of plumbing work. Production Main types of plumbing operations

25.03.2020

Markup.

Workplace locksmith.

Topic 25. Basics of plumbing.

Questions:

1. locksmith work - this is the manual processing of materials, the fitting of parts, the assembly and repair of various mechanisms and machines.

workplace they call a part of the production area with all the equipment, tools and materials located on it, which are used by a worker or a team of workers to complete a production task.

The workplace should occupy the area necessary for the rational placement of equipment on it and the free movement of the locksmith during work. The distance from the workbench and racks to the locksmith should be such that he can use mainly the movement of his hands and, if possible, avoid turning and bending the body. The workplace should have good individual lighting.

locksmith workbench(Fig. 36) - the main equipment of the workplace. It is a stable metal or wooden table, the lid (tabletop) of which is made of boards 50 ... 60 mm thick of hardwood and covered with sheet iron. Single workbenches are the most convenient and common, since on multi-seat workbenches, when several people work at the same time, the quality of precision work is reduced.

Rice. 36 Single locksmith workbench:

1 - frame; 2 - countertop; 3 - vice; 4 - protective screen; 5 - tablet for drawings; 6 - lamp; 7 - shelf for tools; 8 - tablet for a working tool; 9 - boxes; 10 - shelves; 11 - seat

The workbench contains the tools necessary to complete the task. The drawings are placed on the tablet, and the measuring tools are placed on the shelves.

Under the tabletop of the workbench are drawers, divided into a number of cells for storing tools and documentation.

To fix the workpieces, a vise is installed on the workbench. Depending on the nature of the work, parallel, chair and hand vices are used. The most widespread are parallel swivel and non-swivel vices, in which the jaws remain parallel during divorce. The rotary part of the vise is connected to the base with a center bolt, around which it can be rotated at any angle and fixed in the required position with the help of a handle. To increase the service life of the vise, steel overhead sponges are attached to the working parts of the jaws. Chair vise is rarely used, only for work related to shock loading (when cutting, riveting, etc.). When processing small parts, use a hand vise.

The choice of the height of the vice according to the height of the worker and the rational placement of the tool on the workbench contribute to a better formation of skills, an increase in labor productivity and reduce fatigue.

When choosing the height of the installation of the vice, the left hand bent at the elbow is placed on the vise jaws so that the ends of the straightened fingers of the hand touch the chin. Tools and devices are arranged so that it is convenient to take them with the appropriate hand: what is taken with the right hand - hold on the right, what is taken with the left - on the left.

A protective screen made of metal mesh or durable plexiglass is installed on the workbench to retain pieces of metal that fly off during cutting.

Blanks, finished parts and fixtures are placed on racks installed in the area allotted for them.

2. markup - the operation of applying lines (rises) to the workpiece, defining (according to the drawing) the contours of the part and the places to be processed. Marking is used for individual and small-scale production.

Marking is carried out on marking plates cast from gray cast iron, aged and precisely machined.

Lines (risks) with a planar marking are applied with a scriber, with a spatial marking, with a scriber fixed in the thickness gauge collar. Scribers are made of steel grades U10 and U12, their working ends are hardened and sharpened sharply.

Kerner is intended for drawing recesses (cores) on previously marked lines. It is made from steel grades U7, U7A, U8 and U8A.

Marking compass is used to draw circles, divide angles and apply linear dimensions to the workpiece.

3. The main types of plumbing operations.

felling- a locksmith operation, during which excess metal layers are removed from the workpiece with a cutting and impact tool, grooves and grooves are cut out, or the workpiece is divided into parts. The cutting tool is a chisel, a cross-cutting tool, and a hammer is a percussion tool.

cutting is the operation of separating metals and other materials into parts. Depending on the shape and size of the blanks, cutting is carried out with a hand saw, hand or lever scissors.

Hand saw consists of a steel solid or sliding frame and a hacksaw blade, which is inserted into the slots of the heads and secured with pins. A handle is fixed on the shank of the fixed head. A movable head with a screw and a wing nut is used to tension the hacksaw blade. The cutting part of the hacksaw is a hacksaw blade (a narrow and thin plate with teeth on one of the ribs) made of steel grades U10A, 9XC, P9, P18 and hardened. Hacksaw blades are used with a length (distance between holes) of 250-300 mm. The teeth of the blade are spread (bend) so that the width of the cut is slightly greater than the thickness of the blade.

Metal dressing- an operation in which irregularities, dents, curvature, warpage, waviness and other defects in materials, workpieces and parts are eliminated. Editing in most cases is a preparatory operation. Straightening has the same purpose as straightening, but defects are corrected in hardened parts.

bending widely used to give blanks a certain shape in the manufacture of parts. For manual straightening and bending, correct plates, straightening headstocks, anvils, vices, mandrels, sledgehammers, metal and wooden hammers (mallets) and special devices are used.

Klepka- locksmith operation of joining two or more parts with rivets. Rivet connections are one-piece and are used in the manufacture of various metal structures.

The riveting is performed in a cold or hot (if the rivet diameter is more than 10 mm) state. The advantage of hot riveting is that the rod fills the holes in the parts to be joined better, and when cooled, the rivet pulls them together better. When riveting in a hot state, the diameter of the rivet should be 0.5 ... 1 mm smaller than the hole, and in a cold state, by 0.1 mm.

Manual riveting is performed with a hammer, its mass is chosen depending on the diameter of the rivet, for example, for rivets with a diameter of 3 ... 3.5 mm, a hammer weighing 200 g is required.

filing- a locksmith operation, in which a layer of metal is cut from the surface of the part with files to obtain the required shape, size and surface roughness, to fit the parts during assembly and prepare the edges for welding.

Files are steel (steel grades U13, U13A; ShKh13 and 13Kh) hardened bars of various profiles with teeth cut on the working surfaces. The teeth of the file, having the shape of a sharpened wedge in cross section, cut off layers of metal in the form of chips (sawdust) from the workpiece.

Shabreniy the operation of scraping thin layers of metal from the surface of a part with a cutting tool is called - scraper. This is the final processing of precision surfaces (machine guides, control plates, plain bearings, etc.) to ensure tight mating. Scrapers are made of U10 and U12A steels, their cutting ends are hardened without tempering to a hardness of HRC 64...66.

Lapping and polishing– surface treatment operations with especially fine-grained abrasive materials using lapping.

These operations achieve not only the required shape, but also the highest accuracy (5 ... 6th grade), as well as the lowest surface roughness (up to 0.05 microns).

Fitting and assembly work- these are assembly and dismantling works performed during the assembly and repair of machines. Various connections of parts performed during the assembly of machines are divided into two main types: movable and fixed. When performing locksmith and assembly work, a variety of tools and devices are used: wrenches (simple, socket, sliding, etc.), screwdrivers, punches, pullers, devices for pressing and pressing out.

Edit

Edit- an operation by means of which irregularities, curvature or other defects in the shape of blanks are eliminated.

The main equipment for manual straightening of metals are steel or cast iron straightening plates. As a tool for manual dressing, steel hammers with a round head are used; hammers made of soft materials are used for straightening finished surfaces, as well as for straightening workpieces and parts made of non-ferrous metals and alloys.

felling

Cutting is an operation of cold working of metals by cutting. Locksmith and pneumatic hammers serve as percussion tools for cutting, and chisels, crosscutters and groovers serve as cutting tools.

Chisel. The metalwork chisel is made of tool carbonaceous steel. It consists of three parts: shock, middle and working.

The impact part is made tapering upwards, and its top (striker) is rounded; for the middle part of the chisel is held during cutting; the working part has a wedge-shaped shape. The angle of sharpening is selected depending on the hardness of the material being processed.

For the most common materials, the following taper angles are recommended: for hard materials (solid steel, cast iron) - 70 °;

for materials of medium hardness (steel) - 60 °;

for soft materials (copper, brass) – 45°;

for aluminum alloys– 35°.

Kreutzmeisel. To cut out narrow grooves and grooves, a chisel with a narrow cutting edge is used - a crosscut. Such a chisel can also be used to remove wide layers of metal: first, grooves are cut with a narrow chisel, and the remaining protrusions are cut down with a wide chisel.

Locksmith hammers. Locksmith hammers used in cutting metals and are of two types: with round and square heads. The main characteristic of a hammer is its mass. For cutting metals, hammers weighing 400 ... 600 g are used.

To facilitate labor and increase its productivity, mechanized tools are used. Among them, the most common is pneumatic chipping hammer.

metal cutting

For cutting metal, a hacksaw is used, the cutting part of which is a blade. The choice of blade depends on the material of the workpiece, its shape and size. Pipe cutters are used to cut pipes manually. For cutting sheet metal up to 1.5 mm thick, use straight-cutting or curly cutting scissors. The wire is cut with needle nose pliers or power scissors.

filing

filing- an operation in which a layer of metal is removed from the surface of the workpiece using a cutting tool - file.

Purpose of filing- giving parts the required shape, size and specified surface roughness.

Files differ in the number of notches, section profile and length.

By number of teeth, notched to 10 mm in length, the files are divided into 6 classes (0, 1, 2, 3, 4.5).

Depending on the work performed, files are divided into the following types: metalwork - general purpose and for special work, machine, needle files and rasps.

1)General purpose locksmith's files according to GOST 1465-69, eight types are made: flat, square, trihedral, semicircular, rhombic and hacksaw, from 100 to 400 mm long with a notch No. 0-5.

Locksmith's files for special jobs are intended for removing very large allowances when filing grooves, shaped and curved surfaces; for processing non-ferrous metals, non-metallic materials, etc. Depending on the work performed, files of this type are divided into grooved, flat with oval ribs, bars, double-ended, etc.

2)Machine files according to their design, they are divided into rod, disk, shaped heads and lamellar ones. In the process of operation, the rod files are reciprocated, the disk files and shaped heads are rotated, and the lamellar files are in continuous motion along with a continuously moving metal tape.

3)Files according to GOST 1513-67, ten types are manufactured: flat, trihedral, square, semicircular oval, hacksaw, etc. 40, 60 and 80 mm long with a notch of 5 numbers. The length of the file is determined by the length of the working part. Ribs of flat files have a single or double notch. The sides and upper edge of the hacksaw files have a double notch.

Files are used for filing small surfaces and narrow places that are inaccessible for machining with metalwork files.

4)Rasps according to GOST 6876-54, several types are made: general purpose, shoe and ungulate.

Depending on the profile, general-purpose rasps are divided into flat, round and semi-circular with a notch No. 1-2 and a length of 259 to 350 mm.

Holemaking

Drilling is carried out on drilling machines or using manual devices. The main cutting part is the drill, which has two cutting edges. When drilling holes with a diameter of more than 20 mm, pre-drilling the holes with a drill of a smaller diameter is used, then it is drilled to size with a drill of a larger diameter.

After drilling, stamping, cast to obtain a more accurate hole, they are reamed. Depending on the accuracy and purpose of the holes for their processing, countersinks of two numbers are made: No. 1 - for pre-treatment holes and No. 2 for finishing. Structurally, countersinks are of two types: solid hole processing from 10 to 40 mm and mounted - from 32 to 80 mm.

Reaming is used to obtain holes with a more precise shape and low roughness. The operation is carried out using a multi-blade tool - a reamer. Depending on the shape, cylindrical and conical reamers are distinguished. According to the method of application - manual and machine, according to the design - one-piece, mounted, sliding (adjustable) and combined, right and left.

Made part:

Lamb

Detail sketch:

Progress:

1. Processing sharp corners of the workpiece with a bastard file.

2. Marking with a caliper and gauge.

3. Punching along the marking contour for drilling.

4. Drilling.

5. Beating off excess material with a chisel.

6. Processing with files until the required dimensions are obtained.

7. Reaming the central hole with one thread. thread cutting,

8. Polishing with sandpaper.

welding area

The technology of locksmith processing contains a number of basic operations, such as marking, cutting, straightening and bending of metals, cutting of metals, filing, drilling, countersinking, countersinking and reaming of holes, threading, riveting, lapping and finishing, soldering and others. Most of these operations relate to the processing of metals by cutting.

markup

markup called the operation of applying lines (risks) to the surface of the workpiece, showing, according to the drawing, the contours of the part or place to be processed. Markup is divided into:

Linear (one-dimensional) - along the length of bars, rolled products, strip steel,

Planar (two-dimensional) - for sheet metal blanks,

Spatial (volumetric, three-dimensional) - for bulk blanks.

Special marking tools include scribers, center punches, marking compasses, thickness gauges. In addition to these tools, hammers, marking plates and auxiliary devices are used: linings, jacks, etc.

Figure 6 Scribe	Scribers(Figure 6) are used to draw lines on the marked surface of the workpiece. They are made from tool steel U10 or U12 (hardness HRC 58-62). Center punches(Figure 7) is used to apply recesses (cores) on pre-
Figure 7 Punch
marked lines so that the lines are clearly visible and not erased during the processing of parts. Kerner- this is a rod made of tool carbon steel U7, U8 (HRC 52-57) with a length of 100-160 mm and a diameter of 8-12 mm. Sharpening angle - usually 60 °, with more accurate markings - 30-45 °, for the centers of future holes - 75 °. Marking (locksmith) compasses the device is similar to drawing compasses. Reismus(Figure 8) is used to apply parallel vertical and horizontal marks. Recently, a height gauge with a sharp tip is more often used. Planar and especially spatial marking of workpieces is carried out on marking plates. Marking plate is a cast iron casting, the horizontal working surface and the side edges of which are very accurately machined. Template called a device by which parts are made or checked

after processing. Template marking is used in the manufacture of large batches of identical parts. It is expedient because the time-consuming and time-consuming markup according to the drawing is carried out only once during the manufacture of the template. All subsequent operations of marking blanks consist in copying the outlines of the template. In addition, the manufactured templates can be used to inspect the part after the workpiece has been machined.

Straightening and bending of metals

edit called an operation to eliminate defects in workpieces and parts in the form of concavity, convexity, waviness, warpage, curvature, etc. Its essence lies in the compression of the convex metal layer and the expansion of the concave one.

The metal is straightened both cold and hot. The choice of one or another method of dressing depends on the amount of deflection, dimensions and material of the workpiece (part).

Dressing can be manual (on a steel or cast iron straightening plate) or machine (on straightening rollers or presses).

Right Stove , as well as marking, should be massive. Its dimensions can be from 400´400 mm to 1500´3000 mm. Plates are installed on metal or wooden supports, which ensure the stability of the plate and the horizontal position of its position.

For straightening hardened parts (straightening) use straightening grandmas. They are made from steel and hardened. The working surface of the headstock can be cylindrical or spherical with a radius of 150-200 mm.

Manual dressing is carried out with special hammers with a round, radius or plug-in soft metal striker. Thin sheet metal rule mallet(with a wooden mallet).

Check the editing "by eye", and when high requirements to the straightness of the strip - with a curved ruler or on a test plate.

Shafts and round blanks of large cross section are corrected using a manual screw or hydraulic press.

bending metal is used to give the workpiece a curved shape according to the drawing. Its essence lies in the fact that one part of the workpiece is bent relative to the other at any given angle. Manual bending is carried out in a vice using a bench hammer and various devices.

Bending of thin sheet metal mallet .

With plastic deformation of the metal during the bending process, the elasticity of the material must be taken into account: after the load is removed, the bending angle slightly increases.

The manufacture of parts with very small bending radii is associated with the risk of rupture of the outer layer of the workpiece at the bend. The size of the minimum allowable bending radius depends on the mechanical properties of the workpiece material, on the bending technology and surface quality.

Pipe bending is carried out with or without filler (usually dry river sand). The filler protects the pipe walls from the formation of folds and wrinkles (corrugations) in the places of bending.

metal cutting

felling is an operation in which, with the help of a chisel and a metal hammer, layers of metal are removed from the workpiece or the workpiece is cut.

The physical basis of cutting is the action of a wedge, the shape of which is the working (cutting) part of the chisel. Cutting is used in cases where the machining of workpieces is difficult or irrational.

With the help of cutting, metal irregularities are removed (cut down) from the workpiece, hard crust, scale, sharp edges of the part are removed, grooves and grooves are cut, and sheet metal is cut into pieces.

Cutting is usually done in a vise. The cutting of the sheet material into pieces can be carried out on the plate.

The main working (cutting) tool during cutting is a chisel, and a hammer is a percussion tool.

Cold chisel (Figure 8) is made of U7A or U8A carbon tool steel. It consists of three parts: shock, middle and working. shock part 1 it is performed tapering upwards, and its top (the striker) is rounded; for the middle part 2 the chisel is held during cutting; working (cutting) part 3 has a wedge shape.

Figure 8 Bench chisel

The angle of sharpening is selected depending on the hardness of the material being processed. For the most common materials, the following taper angles are recommended:

For hard materials (solid steel, cast iron) - 70 °;

For medium hard materials (steel) - 60°;

For soft materials (copper, brass) - 45°;

For aluminum alloys - 35°.

Kreutzmeisel - a chisel with a narrow cutting edge (Figure 10), designed for cutting narrow grooves, keyways of low accuracy and cutting rivet heads. Such a chisel can also be used to remove wide layers of metal: first, grooves are cut with a narrow chisel, and the remaining protrusions are cut down with a wide chisel.

Locksmith hammers , used in metal cutting are of two types: with round and with square briskly. The main characteristic of a hammer is its mass.

Hammers with a round face are numbered : 1st to 6th . Nominal weight of hammer No. 1 - 200 g; No. 2 - 400 g; No. 3 - 500 g; No. 4 - 600 g; No. 5 - 800 g; No. 6 - 1000 g. Square hammers are numbered from 1 to 8 and weight from 50 to 1000 g.

Hammers material - steel 50 (not lower) or U7 steel.

The working ends of the hammers are heat treated to hardness HRC 49-56 for a length equal to 1/5 of the total length of the hammer from both ends.

For locksmith work, hammers with a round striker No. 2 and 3, with a square striker No. 4 and 5 are used. The length of the hammer handle is approximately 300-350 mm.

metal cutting

Cutting - plumbing operation to separate the whole piece(blanks, parts) into parts. It is carried out without chip removal: with wire cutters, scissors and pipe cutters and with chip removal: with hacksaws, saws, cutters and special methods (gas cutting, anode-mechanical and electric spark cutting, plasma cutting).

The wire is cut with needle nose pliers (nippers), sheet material - with scissors; round, square, hexagonal and strip material of small sections - with hand saws, and large sections on cutting machines with hacksaw blades, circular circular saws, in special ways.

The essence of the operation of cutting metal with needle nose pliers (nippers) and scissors is to separate the wire, sheet or strip metal into parts under the pressure of two wedges (cutting knives) moving towards each other.

Pliers cut (bite off) round steel parts and wire. They are made with a length of 125 and 150 mm (for cutting off wire with a diameter of up to 2 mm) and a length of 175 and 200 mm (for diameters up to 3 mm).

The cutting edges of the jaws are straight and sharpened at an angle of 55-60°. Cutters are made from U7, U8 carbon tool steel or steel 60-70. Sponges are thermally processed to hardness HRC 52-60.

Hand scissors designed for cutting sheet mild steel, brass, aluminum and other metals. They are made in lengths of 200 and 250 mm for cutting metal with a thickness of up to 0.5 mm, 320 mm (for a thickness of up to 0.75 mm), 400 mm (for a thickness of up to 1 mm).

The material of the scissors is steel 65, 70. The scissor blades are heat-treated to a hardness of HRC 52-58. The cutting edges of the blades are sharply sharpened at an angle of 70°. The blades of the scissors in the closed state mutually overlap, and the overlap at the ends does not exceed 2 mm.

Chair scissors cut sheet metal up to 3-5 mm thick. One of the handles of the scissors is bent at an angle of 90° and is rigidly attached to a table or other base. The length of the working handle of the scissors is 400-800 mm, the cutting part is 100-300 mm.

Lever scissors used for cutting sheet metal up to 5 mm thick. The scissors are made from U8A tool steel and heat treated to a hardness of HRC 52-58. The angle of sharpening of the cutting edges of the knives is 75-85°.

Pipe cutters Designed for manual cutting of thin-walled (gas) pipes made of mild steel, cutting is performed without removing chips. They are available in two sizes: for cutting pipes from 1/2 to 2" and for pipes - from 1 to 3".

The main parts of the pipe cutter are rollers: one cutting (working) and two guides. The pipe is cut by a working roller; at the same time, it is fixed on guide rollers and tightened with a screw.

Hand saw (Figure 9, a) is used for cutting relatively thick sheets of metal and round or shaped rolled products. A hacksaw can also be used to cut slots, grooves, trim and cut blanks along the contour, and other work. They are made from U8-U12 or 9XC steels with the hardness of the cutting part HRC 58-61, the core - HRC 40-45. It consists of a frame 1 , tension screw with wing nut 2, handles 6, hacksaw blade 4, which is inserted into the slots of the heads 3 and fastened with pins 5.

Figure 9 Hand saw a - device, b - sharpening angles, c - tooth setting "on the tooth", d - tooth setting "on the canvas".

Each tooth of the blade has the shape of a wedge (cutter). On it, as well as on the incisor, a rear angle is distinguished α, taper angle β , rake angle γ and cutting angle δ= α + β (Figure 9, b). When notching the teeth, it is taken into account that the resulting chips must be placed between the teeth before they exit the cut. Depending on the hardness of the materials being cut, the blade tooth angles can be: γ = 0-12°, β = 43-60° and α = 35-40°. In order for the width of the cut made by the hacksaw to be slightly larger than the thickness of the blade, the teeth are set “along the tooth” (Figure 9, in) or “along the canvas” (Figure 9, G). This prevents the blade from jamming and makes work easier.

filing metal

filing called a locksmith operation, in which layers of material are removed from the surface of the workpiece using a file. It is usually carried out after cutting, peeling or cutting to give the necessary purity and accuracy to the workpiece.

File - it's multi-blade cutting tool, which provides relatively high accuracy and low roughness of the workpiece (part) surface being machined.

With the help of files, planes, curved surfaces, grooves, grooves, holes of various shapes, surfaces located at different angles, etc. are processed.

A file (Figure 10, a) is a steel bar of a certain profile and length, on the surface of which there is a notch (cutting). The notch forms small and sharpened teeth, having a wedge shape in cross section.

notch can be single (simple), double (cross), rasp (point) or arc (Figure 10, b - e).

Files with single cut remove wide chips along the length of the entire notch. They are used for cutting soft metals.

Files with double notch used when filing steel, cast iron and other hard materials, as the cross notch crushes the chips, which makes it easier to work.

Rasp notch obtained by pressing the metal with special triangular chisels. Rasps work very soft metals and non-metallic materials.

Arc notch obtained by milling. It features an arc shape and large tooth gaps for high performance and good quality processed surfaces.

Files are made from steel U10, U12, U13, as well as from alloyed chromium steel ШХ15 and 13Х. After notching the teeth, the files are heat treated to a hardness of at least HRC 54.

By appointment files are divided into the following groups: general purpose, special purpose, needle files, rasps, machine files.

For general plumbing work, general-purpose files are used.

By number of notches files are subdivided into 1 cm length for 6 rooms .

Notched files No. 0 and 1 (bastard) have the largest teeth and are used for rough (rough) filing with an error of 0.5-0.2 mm.

Notched files No. 2 and 3 (personal) are used for fine filing of parts with an error of 0.15-0.02 mm.

Files with a notch No. 4 and 5 (velvet) are used for final fine finishing of products. Processing error - 0.01-0.005 mm.

By lenght files can be produced from 100 to 400 mm.

According to the shape of the cross section they are subdivided into flat, square, trihedral, round, semicircular, rhombic and hacksaw. For processing small parts, small-sized files are used - needle files.

Processing of hardened steel and hard alloys is carried out with special needle files, on the steel rod of which grains of artificial diamond are fixed.

Improving conditions and increasing labor productivity when filing metal is achieved through the use of mechanized (electric and pneumatic) files.

Threading

Threads are single pass formed by one helix (thread), or multiple formed by two or more threads.

In the direction of the helix, the threads are divided into right and left.

According to the shape of the thread profile, they are divided into triangular, rectangular, trapezoidal, stubborn(profile in the form of an unequal trapezoid) and round.

Depending on the sizing system, threads are divided into metric, inch, tubular and etc.

AT metric thread the angle of the triangular profile α is 60°, the outer, middle and inner diameters and the thread pitch are expressed in millimeters. Designation example: M20´1.5 (the first number is the outer diameter, the second is the pitch). In an inch thread, the angle of the triangular profile is 55 °, the diameter of the thread is expressed in inches, and the pitch is the number of threads per inch (1 inch \u003d 25.4 mm). Designation example: l ¼" (outside thread diameter in inches).

A pipe thread differs from an inch thread in that its initial size is not the outer diameter of the thread, but the diameter of the hole of the pipe, on the outer surface of which the thread is cut. Designation example: Pipes ¾" (numbers are the inner diameter of the pipe in inches).

Threading is performed on drilling and special thread-cutting machines, as well as manually. In the manual processing of metals, the internal thread is cut with taps, and the external thread is cut with dies.

Figure 11 Elements and types of thread along the profile a - metric with a triangular profile; b - rectangular; in - trapezoidal symmetrical; g - trapezoidal asymmetric (thrust); d - round.

Taps by appointment divided into manual, machine-manual and machine, and depending on the profile of the thread to be cut- into three types: for metric, inch and pipe threads. Tap(Figure 12) consists of two main parts: the working part and the shank. The working part, in turn, consists of the intake (cutting) and guiding (calibrating) parts. The intaking (cutting) part performs the main work when threading and is usually made in the form of a cone. The calibrating (guide) part, as the name implies, guides the tap and calibrates the hole. Longitudinal grooves serve to form cutting blades with cutting edges and to accommodate chips in the threading process. The shank of the tap serves to secure it in the chuck or in the wrench during operation.

To cut threads of a certain size, manual (locksmith's) taps are usually made in a set of three pieces.

The first and second taps pre-cut the thread, and the third give it the final size and shape. The number of each tap in the kit is marked by the number of notches on the tail. There are sets of two taps: preliminary (rough) and finishing.

Figure 12 Parts and elements of the tap

Taps are made from carbon steels U10A, U12A, high-speed R9, R18, alloyed 9XC, HVSG, etc. (hardness of the working part HRC 59-65, tail - HRC 30-45).

When cutting threads with a tap, it is important to choose the right drill diameter to obtain a threaded hole. The diameter of the hole should be slightly larger than the inner diameter of the thread, since the material will be partially extruded towards the axis of the hole when cutting. The dimensions of the threaded hole are selected according to the tables.

Dies , employees for cutting external threads, depending on the design, are divided into round and prismatic (sliding).

Figure 13 Round plate

Round die(Figure 13, a) is a whole or cut ring with a thread on the inner surface and grooves that serve to form cutting edges and chip exit. Round dies when cutting threads are fixed in a special wrench-die holder(Figure 14).

Figure 14 Die holder (turn)

Figure 15 Prismatic (sliding) die

a - klupp, b - sliding plate

Prismatic (sliding) dies (Figure 15), unlike round ones, consist of two halves, called half-dice. Each of them shows the dimensions of the thread and the number 1 or 2 for proper fixing in a special fixture (kluppe). The angular grooves (grooves) on the outer sides of the half-dies serve to install them in the corresponding protrusions of the die. Dies are made from the same materials as taps.

When cutting an external thread, it is also important to determine the diameter of the threaded rod, since in this case there is some extrusion of the metal and an increase in the outer diameter of the resulting thread compared to the diameter of the rod. The thread diameter is selected according to special tables.

The following questions should be disclosed in the locksmith practice report

1 Locksmith operations

(Define operations and list the tool used.)

2 Characteristics of the main locksmith tools

2.1 Bench chisel

(Give a sketch of the chisel, sharpening angles for cutting different materials, steel grades, hardness.)

2.2 Files

(List the types of files, give a sketch of the file, steel grades, hardness.)

2.3 Taps and dies

(Describe the design of a tap and a round die, give a sketch, material, hardness.)

Basic plumbing operations

markup

Marking is the operation of applying lines (marks) to the surface of the workpiece, defining, according to the drawing, the contours of the part or the places to be processed. Marking lines can be contour, control or auxiliary.

Contour risks define the contour of the future part and show the boundaries of processing.

Control risks are carried out parallel to the contour lines "into the body" of the part. They serve to check the correctness of processing.

Auxiliary risks mark the axes of symmetry, the centers of the radii of curvature, etc.

Marking blanks creates conditions for removing metal allowance from blanks to specified limits, obtaining a part of a certain shape, required dimensions and for maximum savings in materials.

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

The markup is divided into linear (one-dimensional), planar (two-dimensional) and spatial, or volumetric (three-dimensional).

Linear marking is used when cutting shaped steel, preparing blanks for products made of wire, rod, strip steel, etc., i.e. when the boundaries, such as cutting or bending, indicate only one size - length.

Planar marking is usually used in the processing of parts made from sheet metal. In this case, the risks are applied only on one plane. Planar marking also includes the marking of individual planes of complex-shaped parts, if the relative position of the marked planes is not taken into account.

Spatial markup is the most complex of all markup types. Its peculiarity lies in the fact that not only individual surfaces of the workpiece are marked, located in different planes and at different angles to each other, but the location of these surfaces is mutually coordinated with each other.

When marking these types, a variety of control, measuring and marking tools are used.

Straightening and bending of metals

Editing is an operation to eliminate defects in workpieces and parts in the form of concavity, convexity, waviness, warping, curvature, etc. Its essence lies in compressing the convex metal layer and expanding the concave one.

The metal is straightened both cold and hot. The choice of one or another method of dressing depends on the amount of deflection, dimensions and material of the workpiece (part).

Dressing can be manual (on a steel or cast iron straightening plate) or machine (on straightening rollers or presses).

For straightening hardened parts (straightening), straightening headstocks are used. They are made from steel and hardened.

When straightening metal, it is very important to choose the right places to strike. The impact force must be commensurate with the magnitude of the curvature of the metal and reduced as you move from the greatest deflection to the smallest.

With a large bend of the strip on the rib, blows are applied with the toe of a hammer for one-sided drawing (elongation) of the bends.

Strips with a twisted bend are corrected by the untwisting method. Check editing "by eye", and with high requirements for the straightness of the strip - with a curved ruler or on a test plate.

Round metal can be straightened on a plate or on an anvil. If the bar has several bends, then the extreme ones are corrected first, and then those located in the middle.

The most difficult is the editing of sheet metal. The sheet is placed on the plate with the outlet up. Blows are applied with a hammer from the edge of the sheet towards the bulge. Under the action of blows, the flat part of the sheet will be stretched, and the convex part will straighten.

When straightening hardened sheet metal, slight but frequent blows are applied with the toe of a hammer in the direction from the concavity to its edges. The top layers of metal are stretched and the part is straightened.

Shafts and round blanks of large cross section are corrected using a manual screw or hydraulic press.

metal cutting

Cutting is an operation in which, with the help of a chisel and a metalwork hammer, layers of metal are removed from the workpiece or the workpiece is cut.

Cutting is usually done in a vise. Cutting sheet material into parts - can be performed on a plate.

The main working (cutting) tool during cutting is a chisel, and a hammer is a percussion tool.

metal cutting

Depending on the shape and size of the material of the workpieces or parts, cutting during manual metal processing is carried out using a manual or mechanized tool - needle-nose pliers, manual and electric scissors, manual and pneumatic hacksaws, pipe cutters.

The cutting edges of the needle-nose pliers are closed simultaneously along the entire length. In scissors, the convergence of the blades goes gradually from one edge to the other. Their cutting edges do not close, but shift one relative to the other. Both pliers and scissors are a hinged connection of two levers, in which long arms act as handles, and short arms act as cutting knives.

Nippers (nippers) are used mainly for cutting wire. The angle of sharpening of the cutting edges of the needle nose pliers can vary depending on the hardness of the material being cut. For many needle-nosed pliers, it is 55--60 °

Manual scissors (13) are used for cutting steel sheets with a thickness of 0.5--1.0 mm and non-ferrous metals with a thickness of up to 1.5 mm.

filing metal

Filing is a locksmith operation in which layers of material are removed from the surface of the workpiece using a file.

A file is a multi-blade cutting tool that provides relatively high accuracy and low roughness of the workpiece (part) surface to be machined.

By filing, they give the parts the required shape and dimensions, fit the parts to each other during assembly, and perform other work. With the help of files, planes, curved surfaces, grooves, grooves, holes of various shapes, surfaces located at different angles, etc. are processed.

Sawing allowances are left small - from 0.5 to 0.025 mm. The error during processing can be from 0.2 to 0.05 mm and in some cases up to 0.005 mm.

A file () is a steel bar of a certain profile and length, on the surface of which there is a notch (cutting). The notch forms small and sharply sharpened teeth, having a wedge shape in cross section. For files with a knurled tooth, the sharpening angle is usually 70 °, the front angle (y) - up to 16 °, back angle (a) - from 32 to 40 °.

Single cut files cut wide chips along the entire length of the cut. They are used for cutting soft metals.

Double-cut files are used when filing steel, cast iron and other hard materials, as the cross-cut cuts the chips, which makes it easier to work.

Drilling, countersinking, countersinking and reaming

In the work of a locksmith in the manufacture, repair or assembly of parts of mechanisms and machines, it often becomes necessary to obtain a wide variety of holes in these parts. To do this, the operations of drilling, countersinking, countersinking and reaming holes are performed.

The essence of these operations lies in the fact that the cutting process (removal of a layer of material) is carried out by rotational and progressive movements cutting tool (drill, countersink, etc.) relative to its axis. These movements are created using manual (rotary, drill) or mechanized (electric drill) devices, as well as machine tools (drilling, turning, etc.).

Drilling is one of the types of obtaining and processing holes by cutting using a special tool - a drill.

Like any other cutting tool, the drill works on the principle of a wedge. By design and purpose, drills are divided into feather, spiral, centering, etc. modern production mainly twist drills are used and less often special types of drills.

Countersinking is the processing of the upper part of the holes in order to obtain chamfers or cylindrical recesses, for example, under the countersunk head of a screw or rivet. Countersinking is performed using countersinks (20, a, b) or! a drill of a larger diameter; Countersinking is the processing of holes obtained; casting, stamping or drilling, to give them a cylindrical shape, improve accuracy and surface quality. Countersinking is performed with special tools - countersinks (20, c). Countersinks can be with cutting edges on a cylindrical or conical surface (cylindrical and conical countersinks), as well as with cutting edges located on the end (end countersinks). To ensure the alignment of the hole being processed and the countersink, a smooth cylindrical guide part is sometimes made at the end of the countersink.

Countersinking can be a finishing process or pre-deployment process. In the latter case, when reaming, an allowance is left for further processing.

Reaming is the finishing of holes. In essence, it is similar to countersinking, but provides higher accuracy and low surface roughness of the holes. This operation is performed by locksmith (manual) or machine (machine) reamers.

Threading

Threading techniques, and especially the cutting tool used, largely depend on the type and profile of the thread.

Threads are single-start, formed by one helical line (thread), or multi-start, formed by two or more threads.

In the direction of the helix, the threads are divided into right and left.

A thread profile is a section of its coil by a plane passing through the axis of the cylinder or cone on which the thread is made.

For threading, it is important to know its main elements: pitch, outer, middle and inner diameters and the shape of the thread profile

Reading working drawings and sketches

A drawing is an image of objects (for example, machines, mechanisms, instruments), their parts and details with lines, strokes, made with a ratio, and sometimes with an indication of the true dimensions of these objects and giving an idea of their real form and structure.

Eskimz is a preliminary sketch of a structure, a mechanism, or a separate part of it. Sketch -- quick free picture, not assumed to be finished work, often consists of many overlapping lines.

To read a drawing (sketch) means to imagine from the images of the drawing the three-dimensional form of the object depicted on it, the building. In the process of reading the drawing, it is necessary to understand not only the shape as a whole, but also the shape of each part of the whole. It is important to identify the orientation of the object (building) in space and the location of each part relative to each other.

1) get acquainted with the content of the main inscription of the drawing;

2) identify images (views, sections, sections, etc.) that represent the product;

3) carefully consider the images in the drawing to create a primary idea of the shape of the part and its orientation in space. Reveal projection related images of each structural element and mentally imagine their shape. Correlate the mental images with the initial ideas about the shape of the object in order to make sure that the representation of the form is correct. Specify the relative position of each structural element relative to each other for a complete correct representation (understanding) of the shape of the object;

4) imagine the size of the object according to the overall dimensions of the product, affixed to the drawing.

Markup. Drawing needles (scribers) are used to draw lines (marks) on the marked surface of workpieces. Straight lines should be drawn with a scriber with a little pressure along the lower edge of the steel ruler or square (Fig. 39). The part must be stable on a flat base.

Rice. 39. Drawing lines :
a - wrong; b - right

Circles are marked with a measuring compass. Its legs with points are fixed with a locking screw. So that the compass does not move when marking, the center of the hole is marked with a core. In order for the core to be clearly visible, the core must first be held at an angle, set to the intended point, then transferred to a vertical position, without tearing off the end from this point, and with a hammer blow on the core, mark the workpiece (Fig. 40). It is also necessary to core before drilling a hole in order to center the drill.

Rice. 40. Punching

The punching of thin metal plates must be done on a solid base with a light blow of a hammer so as not to pierce the plate through. The markup can be made inaccurately, which leads to a marriage in the manufacture of products, since there is a discrepancy between the marked workpiece and the dimensions indicated on the drawings. The reasons may be different: human inattention, inaccurate installation of the workpiece during marking, inaccuracy of measuring tools. In general, accuracy - in any phase of locksmith work - is the key to success. The caliper is a tool for measuring external and internal linear dimensions (Fig. 41) with an accuracy of 0.05 mm.

Rice. 41. Caliper :
1 - sponges for internal measurements; 2 - movable frame; 3 - depth gauge; 4 - sponges for external measurements; 5 - nonius

It consists of a rod with two fixed jaws, on which a scale scale with a division step of 0.05 mm is applied. A frame also moves along the bar with two jaws and a rod rigidly fastened to it - a depth gauge. The vernier scale is marked on the edge of the frame. The zero stroke of the vernier indicates the number of whole millimeters (in Fig. 41 - 13 mm) on the main scale. Tenths of a millimeter are read on the vernier - where the strokes of both scales coincide (in Fig. 41 - 0.3 mm). Fixed in Fig. 41 size is 13.3 mm. When measuring, the scale must be viewed at a right angle.

Fixing details. The main device for this operation is a vice. They must be completed with various protective sponges (see above). The place of processing should be located as close as possible to the vise jaws. The height at which the vise is installed is very important - your energy consumption when processing parts depends on it. Locksmiths use the following method to determine the optimal height of the vise: bending your right hand, touch your chin with your fist, then try to touch the jaws of the vise with your elbow without extending your arm. If this can be done without bending or standing on your toes, then the vise is set at the required height.

Cutting and cutting of metal. Having finished the markup, they begin to remove the “excessive” fragments of the workpiece. The roughest such operation is cutting, in which the workpiece is cut into pieces with a chisel or crosshead and a hammer, or unnecessary parts are removed. In addition, with the help of cutting, irregularities, scale, sharp edges of parts are removed from the workpieces, grooves and grooves are cut down. Usually this procedure is carried out in a vice, and sheet metal is also cut on a plate. When chopping, it is important to take the correct posture: the body body is straight and half-turned to the axis of the vise; the left foot is half a step ahead of the right; the angle between the feet is about 70°. The chisel should be held in the left hand by the middle at a distance of 15-20 mm from the edge of the impact part. It is installed so that its cutting edge is located on the cut line, and the longitudinal axis of the chisel rod makes an angle of 30-35 ° to the workpiece surface being machined and an angle of 45 ° to the longitudinal axis of the vise jaws (Fig. 42). The hammer force must be significant. The heavier the hammer and the longer its handle, the stronger the blow.

Rice. 42. :
a - side view; b - top view

Sheet and strip metal is cut at the level of the sponges, the wide surfaces of the blanks are above this level (by risks); brittle metals such as cast iron and bronze are cut from the edge to the middle to avoid chipping the edges of the part. Finishing the felling, the impact force should be reduced. For cutting metal blanks and parts, a hacksaw is used more often than other tools. The choice of blade is determined by the thickness and hardness of the metal being processed. For cutting steel and other hard metals, as well as thin-walled pipes and profiles, blades with fine teeth are needed, and for copper, brass, aluminum and other soft metals - with large ones. High-quality blades are marked with the length, width and thickness of the cut, as well as the number of teeth per inch (25.4 mm). For saws with fine teeth, this figure is 28-32, with medium - 18-24, with large -16. Cloths are made from different grades of steel: high-speed (HSS), from bimetallic materials, the latter being more elastic than the former and, accordingly, breaking less. Conventional hacksaw blades are 300 mm long. They are installed in the hacksaw frame with the teeth forward and moderately tightened, since if the tension is too strong, the blade may burst during operation. Before starting processing, the workpiece is firmly fixed in a vice, so that the cut point is as close as possible to the vise jaws. Before starting sawing, it is recommended to make a notch on the workpiece with a triangular file - this will greatly facilitate filing. After that, take the correct posture for sawing. The position of the hands on the hacksaw is shown in fig. 43.

Rice. 43. How to hold a hacksaw

Cutting should start from a plane (with a slight inclination of the hacksaw), but not from the ribs, since in the latter case the teeth of the blade may crumble. Moving the hacksaw with a working stroke (away from you), they make pressure; during the reverse (idle) course, the blade is driven without pressure so that it does not become dull. The highest cutting speed is achieved at 40-50 double hacksaw strokes per minute. For long cuts, the blade must be rotated 90°. In all cases, for more uniform wear of the teeth along the length of the blade, it is necessary to use a larger part. Electric saws and pipe cutters are also used to cut metal blanks. When working with the first, you must wear gloves and goggles. The machine must be held firmly with both hands, otherwise the cutting disc may be distorted. It should, however, be known that with this cutting method coarse burrs are formed, which make it difficult to carry out subsequent processing operations.

When using a pipe cutter, the pipe is clamped in a vice, a pipe cutter is put on it and the cutting roller is brought to the surface of the pipe. By rotating the pipe cutter around the pipe, the movable roller is gradually pressed and thereby cut through the pipe wall. Metal sheets - galvanized tin, copper, aluminum up to 0.5 mm thick - are cut with manual metalwork scissors. Compared to other cutting tools, scissors do not allow material loss. Metal shears cut the same way as others. Their cutting ability is determined by the quality of sharpening and the length of the levers. It is convenient to use scissors with a lever length of at least 20, and best of all - 30 cm. For curved scissors, 20 cm is enough. When cutting a sheet, the scissors are held with the right hand, covering the handles with four fingers and pressing them to the palm (Fig. 44). The little finger or index finger is placed between the handles, retracting the lower handle to the required angle.

Rice. 44. How to hold metal shears :
a - grip with unclenching the scissors with the little finger; b - grip with unclenching the scissors with the index finger

The scissors should be opened approximately 2/3 of their length, since with a larger opening they will not cut, but push the sheet. The sheet is held and fed with the left hand between the cutting edges, guiding the top blade along the marking line. Squeezing the handles with your fingers, cutting is carried out.

Sawing of metals. This one of the most widely used finishing operations consists in removing small layers of metal with a file. With its help, rust, scale are removed from workpieces, rough surfaces are leveled, and parts are given the necessary shape and size. It is clear that in order to carry out such an operation, the master must have a whole set of files. On the working surface of the file there is a notch that forms the cutting edges. Notches are single, double, arc and point. According to the shape of the cross-sectional profile, files are divided into flat, square, trihedral, round, semicircular, rhombic, hacksaw and some others (Fig. 45).

Rice. 45. :
1 - flat pointed (a - double notch; b - single notch; c - ring; d - shank; d - handle); 2 - flat, blunt; 3 - semicircular; 4 - round; 5 - trihedral

The use of a file of one form or another is determined by the profile of the workpiece. Files with a single cut (rectangular at an angle or arcuate) are usually used in the processing of soft metals, as they remove chips along the entire length of the cut. Files with a double (cross) cut remove small chips (due to a large number small cutting wedges), and they are used for filing steel and other hard metals. The working properties of a file are characterized by two related indicators: the notch pitch and the number of notches. The notch pitch is the distance between two adjacent teeth of the file, and the number of notches is the number of them per 1 cm of length. According to the number of notches, bastard files (0-1), semi-personal (2), personal (3) and velvet (4-5) files are distinguished. The latter are used for fine filing, grinding and finishing of parts, while bastard ones are used for preliminary, rough filing. Files with a large notch and coarse, sharp teeth are called rasps, and small and finely notched files are called needle files. Before filing, the part is fixed in a vice, while the sawn surface should protrude 8-10 mm above the level of the jaws. To avoid dents in the workpiece, the soft protective sponges described above can be used. To perform this operation, the following working posture is recommended: half-turned to the vise, the left leg is set forward and half a step to the left, the angle between the feet is 40-60 ° (Fig. 46).

Rice. 46. Pose (a) and grip of the file (b) when filing

The optimal height of the vise should be such that when the file is applied with the right hand to the vise jaws, the shoulder and forearm of this hand form a right angle (Fig. 46a). The file is held by the handle with the right hand so that the rounded end of the handle rests on the palm; the palm of the left hand is applied almost across the axis of the file at a distance of 2-3 cm from the edge of its toe (Fig. 46b). Sawing should be done with a uniform movement of the file: forward - with pressure and when moving back - without pressure. The file must be pressed against the part with both hands, and in different phases of movement in different ways: when the file moves forward, the pressure on the handle is gradually increased with the right hand, while simultaneously weakening the pressure on the toe of the file with the left. The optimal filing speed is considered to be 40-60 double movements (i.e. forward and reverse) per minute. If the surface to be treated is flat, then the main task during processing is to maintain its flatness, that is, to prevent “blockages”. The quality of the sawn planes is evaluated using various control and measuring instruments: flatness - with a curved ruler in the light; the accuracy of adjacent planes processed at a right angle - with a square; parallel processed planes - with a caliper (Fig. 47).

Rice. 47. Ways to control surfaces when filing :
a - with a curved ruler; b - square; c - caliper

There are specific features in the processing of curved surfaces. Convex surfaces are processed using the rocking movements of the file (Fig. 48a), in which it, as it were, goes around the convex surface. Concave surfaces are processed (with round or semicircular files), making intricate movements - forward and to the side with rotation around its axis (Fig. 48b). Control is carried out by marking or using templates.

Rice. 48. Sawing curved surfaces :
a - convex; b - concave

When filing, metal chips clog the notches, so it is necessary to clean the file blade from time to time with a metal brush, which should be moved along the notches. Chalk can be applied to a file with a fine notch. Then the chips will clog less.

drilling. Through this operation, through and non-through holes of various depth diameters are obtained in metal and other materials using drills. The most common drilling tools are manual mechanical and electric drills. Such a tool, however, does not allow precise holes to be drilled, for example for threading. For these purposes, use a drilling stand or drilling machine. The workpiece and the tools used (stand, drill, drills) must be rigidly fixed. This allows you to drill holes of the same depth perpendicular to the surface and adjust the drilling depth. The correct choice of the rotation speed of the drill is also important. Holes of large diameters and hard metals are drilled at low speeds. For drilling metals, spiral (screw) drills with a conical sharpening, made of high speed steel, are usually used. Their blades are made in the form of helical grooves running down to the guide point at a certain angle (Fig. 49). According to this angle (y) and the angle at the top (b), the following types of drills are distinguished (table 6).

Rice. 49. Drills :
H - for hard materials (stone); N - for normal materials (aluminum, copper)

Table 6

In addition to drills made of high-speed steel, drills with hard-alloy (pobedite) tips, which form a particularly wear-resistant cutting edge, are used for drilling especially hard materials. When drilling metal manually, first, the center of the future hole is marked on the workpiece with a center punch, and so that the tip of the drill does not pop out when entering the metal. Having fixed the drill in the chuck, its tip is brought to the intended center of the hole so that the axis of the drill exactly coincides with the axis of the future hole (it is clear that the part must be fixed in one way or another). Drilling should be started at low speed, without pressing hard, smoothly and without jerks, avoiding the swing of the drill. The pressure is gradually increased (if the drill goes in the right direction) and the hole is drilled to the end. An emulsion, lubricating oil, or soapy water should be used to cool the hot drill bit. If these fluids are not available, frequent and long pauses must be made so that the drill cools down. So, in particular, gray cast iron and zinc are drilled. Drilling of sheet metal should be done on a wooden stand located under the sheet.

If a through hole is drilled, when the drill exits the workpiece, the pressure is gradually weakened, and the number of revolutions is also reduced (if possible). If the drill sticks, it must be told to reverse rotation and pulled out of the hole, and then eliminate the cause of the jam. When drilling deep holes, the drill must be periodically removed and cleaned of chips. It is better to drill holes with a diameter of more than 6 mm in two steps: first, drill a pilot hole with a diameter of 4 mm at a shallow depth at the point of punching, and then “put into action” a drill of the desired diameter. During operation, the drills become dull and need to be sharpened. Twist drills are sharpened on an abrasive stone of a grinding machine (Fig. 50). Naturally, this requires some skill. The drill is slightly pressed with a cutting edge to a rotating grindstone, it is led slightly up (against the direction of rotation), while slowly turning it along its axis. The sharpening angle is checked with a special template.

Rice. 50. Drills :
1 - storage; 2 - sharpening; 3 - check

On fig. 50 also shows a way to store drills - in a wooden or plastic block with holes: they can also be stored in a box with holes.

Countersinking. When drilling holes, burrs form on their sharp edges, which can be removed either with a drill of a smaller diameter or with a special conical countersink (Fig. 51a). A countersink is a multi-blade cutting tool used to process previously obtained holes in order to improve their quality and accuracy. In particular, conical countersinking is also used to obtain conical recesses for countersinks of screws and rivets. With an end cylindrical countersink (Fig. 51b), cylindrical recesses are made for the corresponding heads of screws, bolts and nuts. The countersinking operation should be done at the lowest rotational speed of the electric drill with minimal effort.

Rice. 51. :
a - conical; b - cylindrical

Thread cutting. The drilling and countersinking operations described above precede the cutting of internal threads. A thread is a helical groove of constant cross section on an inner or outer cylindrical surface: in the first case, the thread is called internal, in the second - external. Before describing the process of threading, we briefly describe its main types. In the direction of the helix, the thread is divided into right and left. A thread profile is a section of its coil in a plane passing through the axis of the cylinder on which the thread is cut. The main thread parameters are shown in fig. 52. The shape of the profile is as follows: triangular (shown in Fig. 52), rectangular, trapezoidal, persistent (with a profile in the form of an unequal trapezoid) and round.

Rice. 52. Thread parameters :
1 - outer diameter; 2 - inner diameter; 3 - thread length; 4 - thread pitch

In a metric thread, the angle of the triangular profile is 60°, and the thread parameters are expressed in millimeters. For example, the designation M20x1.5 is “translated” as follows: M - metric thread, 20 - outer diameter in mm, 1.5 - pitch in mm. There are other thread systems - inch and pipe. But back to threading. Let's start with the inside. It is cut with a tap, the tail of which is fixed in the collar. For through holes, a tap with a chamfer (lower) part is used on the first 4-5 threads of the thread, which direct the movement of the tap along the walls of the hole. For blind holes, taps with a shorter chamfer (by 2-3 threads) are needed so that the effective (cutting) thread zone reaches almost to the bottom of the hole. For manual threading, taps are usually produced in sets, which include 2-3 tools: roughing, semi-finishing and finishing. The first and second pre-cut threads, the third give it the final size and shape. This stepwise threading significantly reduces the cutting force. Taps are distinguished by the number of notches on the tail: a rough tap has one risk, a semi-finishing tap has two, and a finishing tap has three or none. The double set includes rough and finish taps.

Of no small importance is the correct choice of the diameter of the drill, which drills a hole for the internal thread, and the diameter of the rod - for the external one. The diameter of the drill (and shank) should be slightly smaller than the outside diameter of the thread. The table below gives drill and shank diameters for some common metric thread sizes.

Table 7

Thread diameter, mm	Drill diameter, mm		Rod diameter, mm
Thread diameter, mm	hard metals	soft metals	hard metals	soft metals
M4	3,3	3,3	3,9	3,9
M5	4,1	4,2	4,9	4,8
M6	4,9	5,0	5,9	5,8
M8	6,6	6,7	7,9	7,8
M10	8,3	8,4	9,9	9,8
M12	10,0	10,1	11,9	11,8

Internal threading is performed as follows. The workpiece (part) with a drilled hole is fixed in a vise so that the axis of the hole is strictly vertical. The intake part of the rough tap is inserted into the hole and its installation is checked on the square. The surface of the hole and the cutting part of the tap should be lubricated with a cutting fluid (machine oil for steel, kerosene for cast iron). A collar is put on the tail of the tap. With the left hand, the collar is pressed against the tap, and with the right hand it is turned until it cuts several turns into the metal. After that, they take the knob with both hands and begin to slowly rotate it in this mode: 1-1.5 turns clockwise, 0.5 turns counterclockwise (Fig. 53).

Rice. 53. Internal thread cutting

Reverse rotation is needed to break the chips. At the end of threading with a rough tap, a semi-finishing tap is placed, and then a finishing tap, and the same manipulations are performed with each of them as with a rough tap. All the time, with the help of a square, you need to control the position of the axis of the tap relative to the surface of the workpiece. For cutting external threads, dies with a die holder are used. The same tool is used to update timed threads on bolts, screws and studs. The cutting thread of the die has an intaking (initial) part on one or both sides. In the first case, the die should be adjacent to the stop of the die holder with the opposite side (without the intake part). To avoid thread distortion, a chamfer is removed from the end of the rod (having previously fixed it vertically in a vice). Then the die is installed on the end of the rod perpendicular to its axis and, slightly pressing the die holder with the right hand, turn it with the left (Fig. 54) until the die is firmly cut into the metal.

Rice. 54. External thread cutting

This is achieved after inserting the first threads. After that, pressure is no longer needed, you just need to slowly rotate the plate. The cutting process can be facilitated by simultaneously increasing the purity of the thread by dropping a few drops of machine oil or cutting fluid on the rod and die. External threading is continued until the die has passed the entire required length of the rod. After that, the die is rolled off the rod, they are cleaned of chips and grease, and the cut threads are checked with a reference nut. Chips should be cleaned with a brush, not by hand, to avoid cuts on the sharp cutting edges of the tap or die.

Metal bending. This is a method of processing metals by pressure, in which one part of the workpiece is bent relative to the other at a certain specified angle. Bending is used to give the workpiece the curved shape required by the drawing. Manual bending is carried out in a vice with a hammer and various devices. The force that must be applied in this case, and the sequence of operations during bending, depend on the material, shape and cross section of the workpiece. In this case, it is important to correctly determine the dimensions of the workpiece. They are determined according to the drawing, taking into account the radii of all bends. The easiest way is to bend thin (0.3-1 mm) sheet metal. To accurately bend the part, it is clamped on both sides, up to the bend line, with wooden blocks (mandrels) (Fig. 55).

Rice. 55. sheet metal bending :
a - incorrect; b - correct

In this case, one mandrel is not enough, because the workpiece, clamped in a vise with only one mandrel, leads to the side when the edges are bent. If the workpiece is clamped on both sides, then a good bending quality is obtained. The mandrels must be made of solid wood. For bending, use a mallet (wooden hammer) or an iron hammer with a rubber cap. The workpiece, together with the mandrels, is clamped in a vise and gradually bent along the entire edge, applying light blows with a hammer. It is not recommended to immediately bend completely any section of the workpiece, otherwise the metal will be deformed and the edge will be wavy. The thickness of wooden mandrels should be at least 25-30 mm. A slightly different way is bending a metal sheet along the radius. This is done using a hardwood template (Fig. 56).

Rice. 56. Radius bending of sheet metal

When bending soft, tensile metals, the shape of the template must exactly match the shape of the part being made. When bending elastic metals, its radius should be slightly less than the required one, since in this case the sheet springs. In order to use the lever more efficiently, when bending elastic metals, the sheet is clamped in a vice between two mandrels, one of which is a template, and the other, longer side is carefully struck with a hammer, obtaining the required shape. To achieve tightness, the connection of the blanks is made by the so-called longitudinal lock - a seam seam, or a fold. The fold is used when performing roofing work, connecting ventilation systems, production of buckets, tanks and other products from a tin. The simplest seam seam is called a single lying seam. To obtain it, mark the fold line on the edge of the workpiece, then bend along this line by 90 °. This operation is called flanging. The height of the bent edge, depending on the thickness of the sheet, can be 3-12 mm. After flanging, the workpiece is turned over and its edge is bent another 90°. The same operations are performed with the second workpiece or the second joined edge (Fig. 57).

Rice. 57. Seam blank

The folded edges (folds) of the two sheets are connected to each other. In order for the sheets to be located on the same level, the fold is upset (compacted, in Fig. 58 along the dotted line). To do this, the workpiece is placed on a solid base, clamped, and with the help of a hammer and a hardwood bar, the sheet is first upset, striking along the fold, and then the fold itself (Fig. 59).

Rice. 58. Rebate line

Rice. 59. Seam joint draft

There are cases when the edge of the sheet needs to be reinforced, i.e. give it extra rigidity. This operation is carried out as shown in Fig. 60.

Rice. 60. Making edges with reinforcement. The edge of the sheet acquires additional rigidity if you put a wire under the bend and roll it up:
1 - the edge of the sheet is marked: the width of the bent part is equal to two wire diameters plus double the thickness of the sheet; 2 - the edge is bent at an angle of 90 °; 3 - the edge is folded over a metal gasket; 4 - the edge of the sheet is finally bent on a wooden mandrel

It is also possible to bend in a “cold way” (i.e., without heating) strips of steel of sufficiently large thickness, for example, with a section of 40x45 mm. Such a strip is clamped in a vise and, if possible, first bent by hand to avoid injury from kickback of a long workpiece at the first blows of the hammer. After that, pulling the free end of the workpiece with one hand, strikes with a hammer at the bend. When bending metal strips and bars, templates are often used. In the manufacture of parts with a small bending radius, a thick wire (see Fig. 60) or a pipe of a suitable diameter is used as a template. One end of the workpiece is usually fixed.

Hot bending of metals. Most ferrous and non-ferrous metals used, such as structural mild steel, copper, aluminum and their alloys, etc., can be cold-formed. But some metals - high-quality steels, duralumin - are not always flexible in this way. This becomes possible if the metal being processed is heated. For example, in order to be able to bend steel (without shock loads), it is subjected to heating to red heat. If the steel billet is obtained by forging, then it is better to process it in a state of white heat, since at red and yellow heat the billet is destroyed under hammer blows. Non-ferrous metals and alloys are bent in several steps, in the intervals between which the metal is tempered. Tempering is a type of heat treatment of metals, consisting in the fact that the hardened part is heated to a relatively low temperature, after which it is gradually cooled in the open air or in water. The temperature of the heated hardened part during tempering is estimated by the tint colors, which are obtained as a result of the formation of oxide films of various colors during heating: light yellow (straw) - 220 ° C, dark yellow - 240 ° C, brown-yellow - 255 ° C , brown-red - 265 °С, purple-red - 275 °С, violet - 285 °С, cornflower blue - 295 °С, light blue - 315 °С, gray - 330 °С. Table 8 lists recommended tempering temperatures for some steel tools and parts.

Table 8

Tools (parts)	Recommended holiday temperature, °C
Gauges, templates and other measuring instruments	150-180
Cutting tool from carbon steels: cutters, drills, taps	180-200
Hammers, dies, taps, dies, small drills	200-225
Punches, drills, dies, taps, drills for mild steel and cast iron, scribers, cutters	225-250
Drills, taps for copper and aluminum, chisels, punches, impact tools	250-280
Chisels, woodworking tool	280-300
Springs	300-330
Springs, forging dies	400-500
Parts and tools operating under heavy loads	500-650

At home, small-sized workpieces are heated with a gas burner or blowtorch. During "hot" bending at an angle of 90°C with a minimum radius, the metal at the bend is deformed. This undesirable effect is especially noticeable when bending workpieces of greater thickness. In order for a workpiece of great thickness to retain its cross-section, flattening of the metal is carried out before the bending, as a result of which the bending point thickens, which compensates for its deformation during subsequent bending. When flattening, the metal at the bend is brought to a state of white heat and both ends of the workpiece are cooled so that only the bend itself remains red-hot. After that, the workpiece is upset from the ends, as a result of which the metal thickens in a hot place.

Rice. 61. Hot bending of sheet metal :
a - thin workpiece; b - thick workpiece; c - bending along the radius along the horn of the anvil; g - the same, on a mandrel clamped in a vise

On fig. 61 shows some operations for bending metal in a hot state: a - bending of thin workpieces is performed on top or on the side of the vise jaws; b - workpieces of great thickness - along the vise jaws, if the width of the jaws is not enough, the workpiece is bent along an anvil or steel mandrel; c - bending of blanks along the round horn of the anvil or steel mandrel of the appropriate shape; d - bending along a mandrel clamped in a vise, while the free end of the workpiece contributes to bending due to the lever effect. For relax machining metals, they are often subjected to a special thermal operation - annealing; as a result, the hardness of the metal decreases. Annealing consists in heating a metal object (part, workpiece) to a certain temperature, keeping it at this temperature until it is heated throughout the volume and then, as a rule, slowly cooling to room temperature. Annealing is applied to both ferrous and non-ferrous metals. As a result, the material becomes less rigid and can be easily cold-bent. Table 9 lists the recommended temperatures and coolants for the heat treatment of some steels.

Table 9

steel grade	Recommended temperature, °C			Cooling medium
steel grade	during hardening	on vacation	during annealing	during hardening	on vacation
Steel 30	880	180	845	water	water, oil
Steel 45	860	80	820	-//-	-//-
Steel 55	825	200	780	-//-	-//-
U7, U7A	800	170	780	-//-	-//-
U8, U8A	800	170	770	-//-	-//-
U10, U10A	790	180	770	-//-	-//-
U11, U11A	780	180	750	-//-	-//-
U12, U12A	780	180	750	-//-	-//-
U13, U13A	780	180	750	-//-	-//-