Of all the types of turning tools, the most common are through-cutting tools. They are designed for turning external surfaces, trimming ends, ledges, etc.

The prismatic body of a walking cutter (Fig. 1), like any other, consists of a cutting part (head) and a holder. The head of the cutter contains the front 1, the main back 2 and the auxiliary back 3 surfaces. The intersection of these surfaces form the main 4 and auxiliary 5 cutting edges.

Rice. 1. Structural elements turning tool:

1 - front surface; 2 - main rear surface;
3 - auxiliary rear surface; 4 - main cutting edge;
5 - auxiliary cutting edge

On the front surface, the chips removed by the cutter come off. The main back surface faces the cutting surface formed by the main cutting edge, and the secondary back surface faces the machined surface of the part.

The specified surfaces and cutting edges after sharpening are located at certain angles relative to two coordinate planes and the direction of feed, selected taking into account the kinematics of the machine.

Two mutually perpendicular planes are taken as coordinate planes (Fig. 2):

1) the cutting plane passing through the main cutting edge and the cutting speed vector tangent to the cutting surface;

2) the main plane passing through the same edge and normal to the cutting speed vector.

There is another definition of the main plane: it is a plane passing through the vectors of the longitudinal Spr and radial Sp feeds; in a particular case, it may coincide with the base of the cutter, in which case it is possible to measure the angles of the cutter outside the machine in its static position.

Rice. 2. Geometrical parameters of the through turning tool

For the cutting speed vector, in relation to cutters, as well as to many other tools, the circumferential speed vector of the part is taken without taking into account the longitudinal feed vector, which is many times less than the circumferential velocity vector and does not have a noticeable effect on the magnitude of the front and rear angles. Only in some cases, for example, for drills, at the points of the cutting edges adjacent to the axis of the drill, this influence becomes significant.

On fig. 2 shows the view of the workpiece and the cutter in plan and the geometric parameters that must be indicated on the working drawings of the cutters: γ, α, α1, φ, φ1. Below are definitions and recommendations for assigning their values.

Front and rear corners of the main cutting edge it is customary to measure in the main secant plane N–N, passing normally to the projection of this edge onto the main plane, which in this case coincides with the plane of the drawing. The N–N plane was chosen due to the fact that it is in it that the deformation of the metal occurs during cutting.

Rake angle γ is the angle between the base plane and the plane tangent to the front surface. The value of this angle has a decisive influence on the cutting process, since it determines the degree of deformation of the metal during the transition to chips, the force and heat loads on the cutting wedge, the strength of the wedge, and the conditions for removing heat from the cutting zone. The optimal value of the rake angle γ is determined empirically depending on the physical and mechanical properties of the processed and cutting materials, cutting mode factors (V, S, t) and other processing conditions. Possible values ​​of the angle γ are within 0...30°. To harden the cutting wedge, especially made of brittle cutting materials, a chamfer is sharpened on the front surface with a zero or negative rake angle (γf = 0 ...–5 °), width f, depending on the feed.

Relief angle α is the angle between the cutting plane and the plane tangent to the flank. In fact, this is the angle of the gap that prevents the back surface of the cutter from rubbing against the cutting surface. It affects the intensity of cutter wear and, in combination with the angle γ, affects the strength of the cutting wedge and the conditions for heat removal from the cutting zone.

The lower the load experienced by the cutting wedge and the stronger it is, the greater the value of the angle a, the value of which depends, therefore, on the combination of the properties of the machined and cutting materials, on the feed rate and other cutting conditions. For example, for cutters made of high-speed steel during roughing of structural steels α = 6...8°, for finishing operations α = 10...12°.

Angle of inclination of the main cutting edge λ- this is the angle between the main plane drawn through the top of the cutter and the cutting edge. It is measured in the cutting plane and serves to protect the tip of the tool A from chipping, especially under impact loading, as well as to change the direction of the descending chips. The angle λ is considered positive when the tip of the cutter is lower than other points of the main cutting edge and is the last to come into contact with the workpiece. At the same time, the chips come off in the direction of the machined surface (from point B to point A), which can significantly increase its roughness. When roughing, this is acceptable, since it is followed by a finishing operation that removes these irregularities. But in finishing operations, when the load on the cutting wedge is small, the task of removing chips from the machined surface is of paramount importance. For this purpose, negative values ​​​​of the angle (–λ) are assigned. In this case, the tip of the cutter A is the highest point of the cutting edge, and the chips descend in the direction from point A to point B.

The presence of the angle λ complicates the sharpening of cutters, therefore practical implications this angle are small and are within λ = +5…–5°.

Angles in plan φ and φ 1 (main and auxiliary)- these are the angles between the direction of the longitudinal feed Spr and, accordingly, the projections of the main and auxiliary cutting edges on the main plane.

The entering angle φ determines the ratio between the thickness and width of the cut layer. As the angle φ decreases, the chips become thinner, the conditions for heat removal improve, and thereby the tool life increases, but the radial component of the cutting force increases.

When turning long workpieces of small diameter, the above can lead to their deformation and vibration, in which case φ = 90° is taken.

– when finishing φ = 10...20°;

– when roughing shafts (l/d = 6...12) φ = 60...75°;

– when roughing more rigid workpieces φ = 30...45°.

For through cutters, usually the angle φ1 = 10...15°. As the angle γ1 decreases to 0, the value of h also decreases to 0, which makes it possible to significantly increase the feed and, consequently, the productivity of the cutting process.

Auxiliary relief angle α1, measured in the section N1 - N1, perpendicular to the secondary cutting edge, is assumed to be approximately equal to α; α1 forms a gap between the secondary back surface and the machined surface of the workpiece.

The auxiliary rake angle γ1 is determined by the sharpening of the front surface and is usually not indicated on the drawing.

In order to increase the strength of the cutting part of the cutter, the radius of rounding of its top in the plan is also provided: r = 0.1...3.0 mm. Wherein greater value radius is used in the processing of rigid workpieces, since with an increase in this radius, the radial component of the cutting force increases.

Cutter is the main cutting tool used in machine tools. The cutter consists of two parts: the head (cutting part) and the rod (body), which serves to fix the cutter (Fig. 5, a).

Rice. five. Parts(a) and elements(b) incisor: 1 - front, 2 - rear surface, 3 - cutting edge

The main elements of the cutter head (Fig. 5, b) are:

anterior surface(ABCD) 1, on which the chips come off;

rear surface(ABEF) 2 facing the machined surface;

cutting edge(AB) 3 (see Fig. 5, b), formed by the intersection of the front and rear surfaces. The mutual arrangement of the front and rear surfaces is always such that a wedge-shaped CBE is formed in a section perpendicular to the cutting edge. Depending on the shape and purpose of the cutter, it can have one front and several back surfaces, while the number of cutting edges will be equal to the number of back surfaces. The cutting edges are divided into main, auxiliary and transitional.

The main cutting edge is called the cutting edge, which removes the bulk of the cut metal layer left as an allowance for processing.

Auxiliary cutting edges are edges that remove a small part of the cut layer, they face the machined surface and make a certain angle with the main cutting edge (Fig. 6).

Rice. 6. Surfaces and the elements of the cutter formed by them:

surfaces: 1 - auxiliary back, 3 - front, 6 - main back; edges: 2 - auxiliary cutting, 4 - main cutting; 5 - top

The transitional cutting edge is the edge formed by the mating of the main and auxiliary cutting edges.

Rice. 7. Transitional cutting edge(1) and transitional back surface (2) incisor

Transitional cutting edges are in the form of an arc or chamfer 1 (Fig. 7).

In rare cases, only the main cutting edge is involved in cutting. This happens when the width of the machined surface is less than the length of the main cutting edge (see Fig. 5, b).

The intersection of the main and auxiliary cutting edges forms the top 5 (see Fig. 6) of the cutter.

The main rear surface 6 (see Fig. 6) is the surface adjacent to the main cutting edge.

The secondary rear surface 1 is the surface adjacent to the secondary cutting edge. The transitional rear surface 2 (see Fig. 7) is the surface adjacent to the transitional cutting edge.

The cutters are subdivided according to the direction of feed, according to head shape, on manufacturing method and by type of work performed.

Feed direction incisors are rights And left. The right and left incisors are determined by placing a hand on the incisor. To determine the type of incisor, a hand is placed on it with the palm down so that the fingers are directed towards the top of the incisor; the left is called the incisor, the main cutting edge of which coincides in location with the direction of the thumb of the left hand (Fig. 8, a); right is called a cutter, the main cutting edge of which coincides in location with the direction of the thumb of the right hand.

Rice. 8. Types of cutters:

a - right and left in the form of heads, b - straight, c - bent, d - curved, e - with a drawn head

According to the shape of the head incisors are divided into straight And bent.

Direct(Fig. 8, b) incisors are called incisors, in which the axis of the incisor head is a continuation or parallel to the axis of the incisor body.

bent incisors (Fig. 8, c) are called incisors, in which the axis of the incisor head is tilted to the right or left of the axis of the incisor body. According to the shape of the rod, straight and curved incisors are distinguished. In curved incisors, the axis of the incisor body is curved when viewed from the side (Fig. 8d).

Incisors, in which the working part (head) is narrower than the rod, are called incisors with a drawn head (Fig. 8, e). The retracted head can be symmetrical with respect to the axis of the incisor, retracted to the right, when, when applied to the incisor of the palm of the right hand, the head is shifted towards the thumb of the right hand, or retracted to the left, when when the palm of the left hand is applied, the head is shifted towards the thumb of the left hand.

By manufacturing method distinguish incisors whole And composite.

Solid cutters made from one piece tool material, composite - from two separate parts - a plate and a rod or a head and a rod. Solid cutters made of carbon or alloy tool steel. At composite incisors the heads or blades are made of high-speed steel (the blades are also made of hard alloys), and the rods are made of structural steel. HSS blades or heads are welded, while carbide blades are brazed or mechanically fastened.

By type of work performed cutters are divided into rough and finish through-threads, shaped, cutting, grooving, etc.

People working on metal parts with cutters for lathe for metal, tool sellers are well aware of what types they are divided into. Those who occasionally use turning tools for metal often experience difficulty in choosing the right option. After reviewing the information below, you can easily choose the right metal cutting tool for your needs.

Design features

Each turning tool for metal consists of the following main parts:

• holder. Designed to be fixed on a turning device;
• working head. Used for processing parts.

The working head of the metal-cutting device contains various planes, edges. Their sharpening angle depends on the indicators of the steel from which the part is made, the type of processing. The tool holder for a metal lathe usually has a square or rectangular section.

Structurally, it is possible to distinguish the following types of incisors:

1. Direct. The holder and the head are either on the same axis or on two axes that lie in parallel.
2. Curved. The holder has a curved shape.
3. Bent. If you look at the top of such a tool, you will notice that its head is bent.
4. Drawn. The head has a width smaller than the holder. The axes either coincide or are shifted relative to each other.

Varieties

The classification of turning tools is regulated by the rules of a certain standard. According to its requirements, these devices are divided into the following groups:

1. Whole. Made entirely of alloy steel. There are fixtures that are made from tool steel, but they are rarely used.
2. Devices, on the working element of which carbide inserts for turning tools are soldered. Most common at present.
3. Turning tools with indexable inserts made of hard alloys. The plates are attached to the head with special screws, clamping devices. They are not used as often as other types of models.

Besides, devices differ in the direction of delivery. They may be:

• Leftists. The feed goes to the right. If you put your left hand on top of the tool, the cutting edge will be near the thumb, which is bent.
• Right. They are used most often, the feed goes to the left.

The types and purpose of turning tools form the following classification:

• carrying out finishing processing of the product;
• roughing (peeling);
• semi-finishing;
• execution of operations that require high precision.

From whatever category the metal-cutting tool is, it plates are made of hard alloy materials: VK8, T5K10, T15K6. Occasionally, T30K4 is used. Now there are many types of turning tools.

Straight through

Turning cutters have the same purpose as the bent version, but it is better to cut chamfers with a different device. Usually they carry out the processing of the outer surfaces of steel parts.

The dimensions, or rather, their holders, can be as follows:

• 25 × 16 mm - rectangle;
• 25×25 - square (these models are used for special operations).

Bent through

These types of turning tools, the working head of which can be bent to the left / right, are used for machining the ends of parts. In addition, by means of them it is possible to cut chamfers.

Holders have sizes:

• 16×10 - educational devices;
• 20×12 - non-standard size;
• 25x16 is the most commonly used size;
• 32×20;
• 40×25 - with a holder of this size, they are usually made to order, it is almost impossible to buy them in a store.

All requirements for turning mechanical cutters are spelled out in state standard 18877-73.

Thrust bushings

These types of turning tools can have a straight or bent head, but this design feature is not taken into account in the marking. They are simply called stubborn walkers.

This device, with which the surface of cylindrical metal parts is processed on the machine, is the most popular type of cutting equipment. The design makes it possible to remove from the workpiece in 1 pass a large number of metal surplus. Processing is carried out along the axis of rotation of the part.

The holders of thrust turning cutters are available in the following sizes:

• 16×10;
• 20×12;
• 25×16;
• 32×20;
• 40×25

Bent scoring

It looks like a through passage, but has a different shape of the cutting plate (triangle). By means of such tools, parts are machined in a direction that is perpendicular to the axis of rotation. In addition to bent, there are persistent cutters, but they are rarely used.

Holder sizes are as follows:

• 16×10;
• 25×16;
• 32×20

Cut-off

The turning cutter is very common at the present time. According to its own name, it is used to cut parts at an angle of 90 degrees. Also, through it, grooves of different depths are made. It is quite easy to understand that you have a cutting tool in front of you. It has a thin leg with a hard-alloy plate soldered onto it.

Depending on the design, there are left- and right-hand cutting devices. It's easy to tell them apart. You need to turn the tool over with the cutting plate down and look at which side the leg is on.

Holder sizes are as follows:

• 16×10 - training equipment;
• 20×12;
• 20 × 16 - the most common;
• 40×25

Thread-cutting for external thread

The purpose of these devices is to cut threads on the outside of the part. Usually do metric thread, however, if you change the sharpening, it is possible to create a different type of thread.

The cutting plate, which is installed on this tool, has the shape of a spear. Materials of turning tools - hard alloys.

Thread-cutting for internal thread

With this tool, it is possible to make a thread only in a large hole. This is due to the design features. In appearance, it looks like a boring device for processing blind holes. However, these tools should not be confused. They differ significantly.

Holder dimensions:

• 16x16x150;
• 20x20x200;
• 25x25x300

The holder has a section in the form of a square. Sizes can be set by the first two numbers in the marking. 3rd number - the size of the holder. It determines the depth to which it is possible to thread the thread in the inner hole.

These instruments can only be used on devices equipped with a guitar (special accessory).

Boring for blind holes

The plate has the shape of a triangle. Purpose - processing blind holes. The working head is bent.

Sizes:

• 16x16x170;
• 20x20x200;
• 25x25x300

The largest hole radius that can be machined with a boring tool depends on the holder size.

Boring for through holes

Tools are designed for processing through holes that are created during drilling. The depth of the hole that can be created on the device depends on the size of the holder. The layer of material removed during the operation is approximately equal to the bend of the head.

Today in stores there are boring tools of these sizes:

• 16x16x170;
• 20x20x200;
• 25x25x300

prefabricated

When it comes to the main types of turning tools, it is necessary to mention prefabricated ones. They are considered universal, because they can be equipped with cutting plates for various purposes. For example, by fixing different types of cutting inserts on the same holder, it is possible to obtain tools for processing metal parts on the device at various angles.

Typically, prefabricated cutters are used on devices with a numerical program management or special equipment. They are intended for turning contours, boring blind and through holes, and other turning operations.

When choosing a tool with which metal parts will be processed on a special device, special attention should be paid to the elements of the turning tool. The holder and working head are the most important parts of the cutting fixture. It depends on them how well the processing of the steel billet will be performed, what size holes can be made. If you choose the wrong working tool, you may encounter various difficulties when processing a metal part. It is recommended to study the classification, to understand what this or that product is intended for. Based on the knowledge gained, you will be able to right choice metal cutting tool.

Download GOST

The cutter consists of a holder I (Fig. 1.2), which serves to install the cutter on the machine, and the cutting part (blade) I. The following structural elements are distinguished on the cutting part: the front surface of the blade 7, along which the chips come off; the main back surface of the blade 2, which faces the cutting surface; auxiliary rear surface of the blade 3, which faces the treated surface; main cutting edge 4, which is formed by the intersection of the front and main rear surfaces of the blade (performs the main cutting work); a secondary cutting edge 5, which is formed by the intersection of the front and secondary rear surfaces of the blade; blade top 6, formed by the intersection of the main and auxiliary cutting edges.

Rice. 1.2

1.8. Geometrical parameters of the cutting part of the cutter

The geometric parameters of the cutting part of the cutter include the angles of sharpening the blade and the radius at the top of the cutter.

The geometric parameters of the cutter are considered in statics with respect to two coordinate planes: the main and the cutting plane (Fig. 1.3).

Main plane Rat- a plane parallel to the feed directions of the lathe (5 pr, 5 P) and passing through the main cutting edge of the cutter.

cutting plane RP- a plane passing tangentially to the main cutting edge of the blade and perpendicular to the main plane.

To determine the actual values ​​of the sharpening angles of the cutter, we draw the main secant plane P t.

Principal cutting plane RX- a plane passing perpendicular to the line of intersection of the main plane and the cutting plane. This section is shown in Fig. 1.4.

The main sharpening angles include:

rake angle y - the angle between the front surface of the blade and the main plane (measured in the main cutting plane);

main clearance angle a - the angle between the main rear surface of the blade and the cutting plane (measured in the main cutting plane);

the main angle in terms of cp - the angle between the projection of the main cutting edge on the main plane and the direction of movement of the longitudinal feed;

auxiliary angle in the plan (p 2 - the angle between the projection of the auxiliary cutting edge on the main plane and the direction opposite to the movement of the longitudinal feed.

The geometric parameters of the cutting part of the cutter are selected depending on the material being processed and other processing conditions.

To measure the sharpening angles of the cutter, a special device is used - goniometer.

Goniometer (Fig. 1.5) consists of a base 1 , upright 2 and scale device 3 with measuring ruler 4 , which can be rotated around an axis 6. The scale device is guided along the rack and, if necessary, can be rotated around the axis of the rack, fixing in any position in height. The position of the rotary measuring ruler is fixed with screw 5.

Rice. 1.5

When measuring the angles y and a, the measuring ruler is set perpendicular to the main cutting blade of the cutter. When measuring the front angle of a ruler 4 coincides with the front surface of the cutter, and when measuring the main rear angle a - with the main rear surface. According to the readings of the goniometer scale, the value of the angles is determined.

Questions for self-examination

List the shaping movements.

What is the main cutting motion?

What is a feed motion?

What is called the processing mode (cutting mode)?

What. depicted in the processing scheme?

What units are used to measure the speed of the main movement of cutting and feed during turning?

What is the main design feature of any cutting tool?

Name the parts, elements and geometrical parameters of a turning straight cutter.

T e m a 2. PROCESSING OF WORKPIECES BY TURNING

Target- study of the technological possibilities of turning, the main components of the screw-cutting lathe and their purpose, tools for performing different types turning works; obtaining practical skills in setting up the machine and working on it.

Purpose and scope of turning

Technological equipment

Installation of blanks

Turning tool

Kinematic methods of shaping surfaces by turning

Questions for self-examination

Purpose and scope of turning

Turning- a type of blade cutting with a rotational main cutting motion imparted to the workpiece and a translational feed motion imparted to the tool. Turning processes the surfaces of bodies of revolution on all types of lathes. Turning produces external and internal cylindrical, conical, shaped, threaded, end surfaces, as well as annular grooves of various types.

The main types of turning operations: turning (turning the outer surface), boring (turning the inner surface), cutting the end face, chamfering, cutting off, threading, drilling, rolling (see topic 10), etc.

Technological equipment

The universal screw-cutting lathe model 1K62 is shown in fig. 2.1. bed 1 is the basis for all other machine components. In the headstock 3 there is a gearbox, which serves to change the speed of the spindle - the main shaft of the machine. A chuck is installed on the right spindle flange to secure the workpiece and transmit torque to it. 15.

Gearbox 2 allows you to change the speed of rotation of the drive shaft 13 and lead screw 12, which provides longitudinal and transverse feed of the cutting tool.

caliper 8 consists of a longitudinal 4, transverse 7 and upper 6 calipers, as well as a four-position tool post 5. caliper 8 moves along the guides 11 bed, which ensures the movement of the cutter along the axis of rotation of the workpiece. The transverse support moves the cutter along the guides of the longitudinal support perpendicular to the axis of rotation of the workpiece. There is a turntable between the top and cross slides, which allows you to set the top slide at an angle to the machine center line (a line passing through the axis of rotation of the spindle and the axis of the tailstock center 10).

in an apron 14 mounted mechanisms that convert the rotational movement of the running shaft 13 (or lead screw 12) in the translational movement of the longitudinal and transverse calipers (longitudinal and transverse feed movements). lead screw 12 works only when cutting threads with threaded cutters.

In the tailstock housing 10 quill moves in axial direction 9. A center with a tapered shank is installed in the quill, supporting the workpiece, or a cutting (axial) tool for making holes. Shield 16 protects the worker from flying chips during cutting.

Installation of blanks

Workpieces on the machine are installed using chucks or in centers with a driving faceplate (Fig. 2.2). For clamping workpieces whose length-to-diameter ratio is b/a< 4, use self-centering three-cam (see Fig. 2.2, but), four-jaw (non-self-centering) and collet chucks.

Rice. 2.2

Workpieces with a ratio b/a > 4 are installed in centers with a driving faceplate. In this case, the rotation from the spindle to the workpiece is transmitted by a drive faceplate with a pin fixed on the flange of the machine spindle (Fig. 2.2, b) and a drive collar (see Fig. 2.2, in), attached to the workpiece.

The centers are installed in the conical holes of the machine spindle and tailstock quills. By design and purpose, the following types of centers are distinguished (Fig. 2.3):

thrust (see Fig. 2.3, but)- used when turning cylindrical surfaces;

cut (half-center) (see Fig. 2.3, b)- used for processing the end face of the workpiece;

with ball bearing (see fig. 2.3, c)- designed for turning a conical surface by shifting the tailstock;

reverse (see Fig. 2.3, d) - used to install workpieces of small diameters (up to 4 mm);

rotating (see Fig. 2.3, b) - designed to install workpieces with a large section of the cut layer (when significant cutting forces occur during the cutting process), as well as for processing workpieces with a high spindle speed.

For fixing in the centers on the workpiece, it is necessary to provide standard center holes (Fig. 2.3, e).

Rice. 2.3

When processing non-rigid workpieces (b/d, > 10) use steady rests designed to create additional support in order to prevent deflection under the action of cutting forces. The fixed steady rests are installed on the bed guides, the movable ones - on the longitudinal support.

Turning tool

Lathes use turning cutters, axial tools (drills, countersinks, reamers and other tools, the purpose and classification of which are discussed in the study of topic 6), as well as a tool for surface treatment without chip removal (see topic 10).

According to their purpose, turning cutters are divided into through, cutting, cutting, shaped, boring, contour, etc. In table. 2.1 shows the main types of turning tools.

By design, through cutters are divided into straight, persistent, bent, and according to the location of the main cutting edge - into right and left. The cutting edge of the right through cutter is located so that it can cut material from the workpiece when the cutter is moved from right to left, and the left through cutter - from left to right. Through cutters are used mainly for turning cylindrical and conical surfaces. A straight cutter can be used for cutting the end, and a straight cutter can be used for turning a stepped shaft. Scoring turning tools are intended only for processing end surfaces.

Cut-off cutters cut off the finished product (part from the workpiece). Shaped cutters intended for processing shaped surfaces are considered in the study of topic 3, and threaded cutters - topic 4. Boring cutters are used for boring through and blind holes in blanks (castings or forgings) with holes; in solid blanks, holes are obtained by drilling with twist drills, and then processed with countersinks and reamers (see topic 6), as well as boring cutters.

Kinematic methods of shaping surfaces by turning

The surfaces of revolution are obtained by moving the generatrix along the guide, which is a circle (Table 2.2). The generating line can be of any shape and be located arbitrarily relative to the guide.

When turning, the guide circle is always reproduced by the rotational movement of the workpiece, and the generatrix is ​​reproduced by moving the tool. For shaping by turning, two kinematic methods are used: traces and copying, or a combination of both (for example, when threading).

When processing using the trace method, the generatrix is ​​reproduced by the trajectory of the top of the turning tool as it moves relative to the workpiece (see Table 2.2) in a straight line.

When processing by the copying method, the generatrix repeats the shape and dimensions of the main cutting edge of the tool on the machined surface of the workpiece.

The copying method processes short surfaces of parts of any shape. The trace method is used for turning surfaces of revolution of any shape without limiting the length of processing.

What kind of work is done on lathes?

What movements of the workpiece and tool are used in the formation of surfaces by turning?

Explain the essence of kinematic methods of shaping traces and copying.

List the main components of the screw-cutting lathe.

What types of tools are used in turning?

List the methods of fixing workpieces and devices used for this purpose.

TemaZ. PROCESSING OF CONICAL AND SHAPED SURFACES

Target- study of the technological possibilities of processing conical and shaped surfaces on a screw-cutting lathe, used cutting tools; acquiring machine setup skills and independent work On him.

Methods for processing conical surfaces

cutting tool

Characteristics of methods for processing conical surfaces

Machining shaped surfaces Questions for self-examination

Methods for processing conical surfaces

The main geometric parameters of the cone (Fig. 3.1): IN And (1 - diameters of the bases of the cone, mm; I- cone length (distance between bases), mm; but- cone slope angle, deg; 2a - cone angle, deg.

The processing of conical surfaces by turning on screw-cutting lathes is ensured by the rotation of the workpiece (the main cutting movement ING) and tool movement (feed movement Vd). Depending on the method, the feed can be longitudinal, transverse, inclined (Table 3.1). With simultaneous uniform movement of the cutter parallel and perpendicular to the axis of rotation of the workpiece, a conical surface will also be formed. This method is used on lathes with numerical control (CNC).

Table 3.1

cutting tool

External conical surfaces are processed with through cutters, internal - with boring ones (see topic 2). To obtain conical holes, a cylindrical hole is pre-drilled in a solid workpiece. Then, depending on the size and required accuracy, it is processed with countersinks, countersinks, reamers (see topic 6), as well as boring cutters.

Characteristics of methods for processing conical surfaces

Wide cut. The shaping of conical surfaces with a wide cutter (Fig. 3.2) is carried out by copying. The cutter is installed in the tool holder so that the main angle in the plan<р был равен углу уклона конуса а. Длина главной режущей кромки лезвия должна быть на 1... 3 мм боль­ше длины образующей конической поверхности. Резцу сообщают движение подачи в поперечном или продольном направлении. Способ наиболее широко используют для снятия фасок.

turn upper caliper . The shaping of conical surfaces by turning the upper support (Fig. 3.3) is carried out by the trace method. The upper caliper is rotated at an angle a to the center line of the machine. Feed movement Vdn(inclined feed) set the cutter manually by turning the handle /. The axis of rotation of the workpiece coincides with the line of centers of the machine.

FROM using a ruler. The shaping of conical surfaces using a copy ruler (Fig. 3.4) is carried out by the trace method. A plate is attached to the machine bed 1 with a copy ruler 2 along which the slider moves 3, connected to the cross support of the machine 5 with a rod 4. When moving the longitudinal support, the cutter installed in the tool holder on support 5 receives two movements: longitudinal from the longitudinal support and transverse from the copier ruler 2. As a result of the addition of two feed movements, the cutter moves along the generatrix of the machined surface at an angle a to the line of centers of the machine. The angle of rotation of the ruler, corresponding to the angle of the slope of the cone, is set according to the divisions on the plate 1. This method provides high processing accuracy.

Offset of the tailstock in the transverse direction. The shaping of conical surfaces by shifting the tailstock in the transverse direction (Fig. 3.5) is carried out by the trace method. The workpiece is installed in the centers at an angle a to the line of machine centers so that its axis of rotation coincides with the axis of the conical work surface. To do this, the tailstock of the machine is shifted in the transverse direction along its guides by an amount H = 11% And where I is the length of the cone. In this case, the generatrix of the conical surface will be parallel to the line of the centers of the machine. Processing is carried out using the feed movement of the cutter in the longitudinal direction. The method does not provide high processing accuracy.

Rice. 3.4

Rice. 3.5

Conical countersink or reamer. Shaping with a conical countersink or reamer is carried out by the trace method. In this case, the tool is fixed in the tailstock quill. From the tailstock handwheel, the tool receives a (manual) feed motion in the longitudinal direction.

Processing of shaped surfaces

Shaped surfaces include surfaces, the generatrix of which can have any shape other than a straight line. The shaped surfaces of bodies of revolution are processed by turning.

Shaped surfaces with a length of not more than 50 mm are processed with special shaped cutters, the profile of which determines the shape of the generatrix. Surface shaping is carried out by copying. In this case, the cutting tool receives a transverse feed motion.

By design, shaped cutters are divided into the following types:

Round and prismatic shaped cutters are fixed in the tool holder in special holders, and the round cutter is set above the center line of the machine by an amount to(See Figure 3.7).

Long shaped surfaces are processed with through cutters using a shaped copier, which is similar to a copier ruler for processing conical surfaces (Fig. 3.9). Surface shaping is carried out by the trace method.

When moving the caliper in the longitudinal direction B$ P r the cutter receives movement in the transverse direction from the copier. As a result of the addition of these two movements, the shaped surface of the workpiece is formed.

The processing of shaped surfaces can be performed with contour cutters (see topic 2, table 2.1) on CNC lathes.

Questions for self-examination

How are external conical surfaces obtained on a screw-cutting lathe?

In what ways can the inner conical surface be machined on a screw-cutting lathe?

Rice. 3.9

How is the outer conical surface treated with a cone angle at the apex of 60° and a generatrix length of 100 mm?

What tools are used to process the outer and inner conical surfaces?

Name the methods of processing shaped surfaces and the tools used.

What methods of shaping produce conical and shaped surfaces by turning?

Topic 4. THREADING

Target- study of the technological possibilities of thread cutting methods on a screw-cutting lathe, the thread-cutting tool used; obtaining practical skills in setting up a machine for threading and independent work on it.

Threading characteristic. Types and purpose of thread

Kinematics of thread shaping

Kinematic diagram of a screw-cutting lathe model 16K20

Setting up the machine for threading Questions for self-examination

1. Threading characteristic. Types and purpose of thread

thread-cutting- a type of blade cutting, which consists in the formation of a thread. carving called a helical surface of a certain profile, formed on the outer or inner surface of the workpiece. In this case, the workpiece is a body of revolution (cylindrical or conical shape).

Rice. 4.1

Threads are distinguished by the following features:

by location - external and internal;

along the profile - triangular (Fig. 4.1, a, b) trapezoidal (Fig. 4.1, c), rectangular (Fig. 4.1, d), thrust (Fig. 4.1, e) and round (Fig. 4.1, e);

by step - metric (step R given in mm), inch (pitch R given by the number of threads per inch; 1 inch = 25.4 mm) and modular - thread pitch P = pt, where T- gear module, mm

(see topic 8). The metric thread has a triangular profile with an apex angle of 60°, the inch thread has 55°, the modular thread has a trapezoidal profile with an apex angle of 40°;

by the number of helical grooves - single-start and multi-start;

in the direction of helical grooves - right and left;

by appointment - fastening and running.

To obtain fixed detachable connections, fastening threads (triangular profile) are used. Metric threads are cut on fasteners (screw, bolt, nut, etc.) and on small lead screws, inch - in pipe connections. To obtain movable joints, a running thread is used. Rectangular and trapezoidal threads are used in the lead screws of machine tools and other mechanisms. Round threads are used in ball screws; persistent - in jacks and screw presses; modular - in worm screw gears.

Kinematics of thread shaping

Threading is carried out by a combination of two kinematic methods: copying and traces (see topic 2, table. 2.2).

The thread profile is created by copying the profile of the cutting part of the tool, and the helical line is formed using the trace method with a combination of the rotational movement of the workpiece (the main cutting movement P) d) and the translational movement of the cutter (longitudinal feed Dd-pr) along its axis. These movements must be precisely coordinated: in one revolution of the workpiece, the tool must move by the pitch of the single-start thread P n (one helix on the workpiece) or the lead of the multi-start thread (the thread lead is equal to the product of the pitch P n of the multi-start thread by the number of starts TO). This condition is ensured by the kinematic connection of the machine spindle and the lead screw (Fig. 4.2).

R X - ta.- hodgtt) shtsh R and ■> ite trrez & schshh threads k "- chpe.t shh<м)т резьбы

Rice. 4.2

On screw-cutting lathes, threads can be cut with various tools: thread cutters, taps, dies, etc.

Threading with turning threaded tools is a universal method that allows you to cut threads of any kind.

External cutting patterns ( but) and internal (b) threads with threaded cutters are shown in fig. 4.3.

A tap and a die are used for threading a triangular profile (Fig. 4.4). When threading with a die (see Fig. 4.4, but) or a tap (Fig. 4.4, b), the machine setting is limited to setting the specified speed of the workpiece. The tap and die are installed in special holders. At the initial moment, the tool receives a forced longitudinal feed, which is performed manually, for a length of two or three threads. Further movement of the tool occurs due to self-screwing.

Rice. 4.4

Kinematic diagram of a screw-cutting lathe model 16K20

The machine can cut all types of threads discussed above. When threading with a threaded cutter, the machine uses a chain of the main movement and a screw-cutting chain, and when cutting with a tap and a die, only the chain of the main movement is used, since the tool is fed by self-screwing.

On fig. 4.5 shows a part of the kinematic diagram of the machine involved in the transfer of the main cutting movement to the workpiece, and in fig. 4.6 - part of the kinematic diagram that provides the movement of the feed to the tool when threading.

Rice. 4.5

Rice. 4.6

Chain of the main movement(see Fig. 4.5) sets the rotational movement of the machine spindle (shaft VI). From the electric motor M (LG = 10 kW, n = 1460 min -1) through a V-belt drive and a gearbox, the spindle can receive 24 different speeds in the range of 12.5 ... 1600 min -1 (Table 4.1) and at the same time have forward and reverse rotation.

Screw chain(longitudinal feed chain) coordinates the rotational movement of the workpiece and the translational movement of the threaded cutter along the axis of the workpiece so that in one turn of the workpiece the cutter moves one step (if the thread is single-start) or one move (if the thread is multi-start). The initial link of this chain is the machine spindle, then the movement goes through the feed box. The final link is the lead screw of the machine with a pitch RX - 12 mm (see fig. 4.2). The setting for the pitch of the thread being cut is carried out using a guitar of replaceable gears (K, b, M, U) and feed boxes (see Fig. 4.6).

Table 4.1

The kinematic balance equation for a screw-cutting chain has the form

60 30 25 K M.P 60 " 25 " 45 " T" ~

where g k. p is the gear ratio of the feed box. This equation is used in the derivation of calculation formulas for the selection of replacement guitar wheels for threads with a pitch Rn, equal to the tabular RT or different from it.

Table 4.2

The feed box (see Fig. 4.6) has two main kinematic chains. One chain is used for cutting inch threads. In this case, the movement is transmitted to the lead screw when the clutches Mg, Mz, M 4 and Me are turned off, and the M5 clutch is turned on:

28 38 25 / 30 35 28\ 30 18

Pval1X ‘ 28 ’ 34 "30 \ And 48’ 28’ 35 y 33 ’ 45

Another chain is designed for cutting metric and modular threads. In this case, the M2 and Mb clutches are off, and the M3, M4 and M5 clutches are on:

28 30 /42 28 35\ 18 / 28\ 15

p In al1X "28" 25 \ 30’ 35 5 28 ) 45 35) 48

When cutting metric and inch threads, replaceable guitar gears are installed

T"N ~ 86 ’ 64’

and when cutting modular threads

K M _ 60 86 T'N' 73" 36*

When cutting threads with a pitch P n that differs from the table RT, replaceable gear wheels of the guitar are selected by calculation. The selection of wheels is carried out according to a pre-selected value of the gear ratio of the feed box (we will take the gear ratio of the feed box equal to one).

Setting up the machine for threading

Setting up the machine for threading is carried out in the following order:

P\u003d u-HIO-60 / ^ min -1, where V- given cutting speed, m/s;<7 - диаметр заготовки, мм. Полученное значение P correct according to the table. 4.1;

according to the table 4.2 we determine the correspondence of the specified pitch of the thread being cut to the table value;

if the specified pitch corresponds to the table, then you can cut the thread without special settings, using the indications for the position of the feed box handles located on the machine;

if the specified pitch does not correspond to the tabular one (see table. 4.2), then for threading it is necessary to perform a special setting, using the calculation formula to determine the gear ratio of the guitar of interchangeable wheels.

For example, for a metric thread, the calculation formula is

K M __ 5 Rp T "lG" 8 ~R~T"

where Rn- thread pitch, RG- the tabular value of the pitch closest to the pitch of the thread being cut.

Based on the calculation results, replacement wheels are selected from the following set: 36, 40, 44, 45, 46, 48, 50, 52, 54, 56, 57, 60, 64, 65, 66, 70, 72, 73, 75, 80, 86, 90, 127 (all gears have the same module t = 2 mm).

Thread cutting depending on the pitch Rn carried out in several passes.

Distinguish between even and odd threads. Even call a thread in which the ratio of the pitch (stroke) to the pitch of the lead screw of the machine (or vice versa) is an integer, and odd- the one in which the specified ratio is fractional. This division defines the machine setting techniques that are used in threading.

When cutting an even thread, at the end of the passage, the cutter is moved to its original position manually or mechanically (accelerated) with the lead screw split nut open. The kinematic connection of the spindle and the lead screw ensures the possibility of turning on the split nut of the lead screw at any position of the cutter relative to the thread and guarantees its precise entry into the cut groove of the thread.

When cutting an odd thread after each working pass, the cutter is retracted from the workpiece in the transverse direction, the caliper is switched to reverse and, without opening the split nut, the cutter is retracted to its original position. Then the cutter is set to the specified cutting depth and the next pass is performed. >

Consider setting up the machine with an example.

Example.

Need to cut metric threads in increments Rn = 5.5 mm. Workpiece outer diameter R) - 40 mm. Workpiece material - structural steel. The material of the cutter is high-speed steel. Cutting speed y= 0.33 m/s.

Solution".

according to the given cutting speed, we calculate the spindle speed:

Psp = 1000 60 uCpi) = 1000 60 0.33 / (3.14 40) \u003d 159 min "1.

The resulting value p w = 159 min -1 is corrected according to the table. 4.1. To set up the machine, we take the closest to the calculated tabular value - p w = 160 min -1;

TO M_ 5 РЪ_ 5 55 _ 5 55 _ 5 I _ 50 66 b ’ N~ 8' P t ~ 8" 6" 8' 60 ~ 8" 12" 80" 72"

The number of teeth of interchangeable wheels is selected from a set of interchangeable wheels: fig> 4.7

K = 50, b = 80, M = 66, N = 72.

We check the adhesion condition of the selected interchangeable gears (Fig. 4.7):

For design reasons, guitar gears should have the following tooth numbers: TO < 88, N < 73; TO + b + M > 260.

the replaceable wheels selected by calculation are installed on the machine. At the same time, we adjust the feed box with the help of handles per step RT = 6 mm.

Questions for self-examination

What types of threads can be cut on lathes?

Which thread is called even and which is odd?

Name the methods for setting up the machine for cutting even and odd threads.

What cutting tool is used when cutting external and internal threads?

Describe the kinematics of threading with dies and taps.

Specify the purpose of the chain of the main cutting motion.

Specify the purpose of the feed chain when cutting threads.

How is the machine set up for threading with a step equal to the table (see Table 4.2)?

How is the machine set up when cutting threads with a step different from the table?

How to choose replacement guitar gears?

T e m a 5. MULTI-TOOL PROCESSING OF BLANKS

Target- study of the technological possibilities of multi-tool processing on a turret lathe, the main components of the machine and their purpose; the acquisition of practical skills in setting up the machine and independent work on it.

Characteristics of multi-tool processing

Purpose and design features of the turret lathe

The main components of the turret lathe model 1K341

Setting workpieces and cutting tools

Machine setup

Questions for self-examination

When working on lathes, various cutting tools are used: cutters, drills, countersinks, reamers, taps, dies, shaped tools, etc. Turning cutters are the most common tool, they are used for processing planes, cylindrical and shaped surfaces, threading, etc. e. The elements of the cutter are shown in the figure. The cutter consists of a head (working part) and a rod that serves to fix the cutter in the tool holder. The front surface of the cutter is the surface along which the chips come off. Back (main and auxiliary) are the surfaces facing the workpiece. The main cutting edge performs the main cutting work. It is formed by the intersection of the front and main back surfaces of the cutter. The secondary cutting edge is formed by the intersection of the front and secondary rear surfaces. The top of the cutter is the intersection of the main and auxiliary cutting edges.

To determine the angles of the cutter, the concepts are established: the cutting plane and the main plane. The cutting plane is the plane tangent to the cutting surface and passing through the main cutting edge of the cutter (see figure). The main plane is called the plane parallel to the direction of the longitudinal and transverse feeds; it coincides with the lower supporting surface of the cutter. The angles of the cutter are divided into main and auxiliary (see figure). The main angles of the cutter are measured in the main cutting plane, i.e., the plane perpendicular to the projection of the main cutting edge onto the main plane.

The main clearance angle α is the angle between the main rear surface of the cutter and the cutting plane. Pointing angle β is the angle between the front and main rear surfaces of the cutter. The main rake angle γ is the angle between the front surface of the cutter and the plane perpendicular to the cutting plane and passing through the main cutting edge of the cutter. The sum of angles α+β+γ=90 degrees. The cutting angle δ is the angle between the front surface of the cutter and the cutting plane. The main angle in terms of φ is the angle between the projection of the main cutting edge on the main plane and the feed direction. Auxiliary angle in terms of φ1 is the angle between the projection of the secondary cutting edge on the main plane and the feed direction. The angle at the top in terms of ε is the angle between the projections of the main and auxiliary cutting edges on the main plane. The secondary clearance angle α1 is the angle between the secondary clearance surface and the plane passing through the secondary cutting edge perpendicular to the main plane. The angle of inclination of the main cutting edge λ is the angle between the main cutting edge and the plane passing through the top of the cutter parallel to the main plane. The cutters are classified: in the direction of feed - into right and left (right cutters on a lathe work when fed from right to left, that is, they move to the headstock of the machine); according to the design of the head - into straight, bent and drawn (see figure);

Incisors: a - straight, b - bent, c - drawn

according to the type of material - from high-speed steel, hard alloy, etc.; according to the manufacturing method - into solid and composite (when using expensive cutting materials, the cutters are made composite: the head is made of tool material, and the rod is made of structural carbon steel; composite cutters with hard alloy plates that are soldered or mechanically fastened are most widely used); according to the cross section of the rod - into rectangular, round and square; according to the type of processing - for through-hole, cutting, cutting, slotted, boring, shaped, thread-cutting, etc. (see figure).

Turning cutters for various types of processing:

a - external turning with a curved through cutter, b - external turning with a straight through cutter, c - turning with cutting the ledge at a right angle, d - cutting a groove, e - turning a radius fillet, e - boring a hole, g, h, i - threading external, internal and special