The structure of a lathe - how does it work? Turning materials Bed design

In fact, the design of a lathe, regardless of its model and level of functionality, includes standard structural elements that determine the technical capabilities of such equipment. The design of any machine belonging to the category of turning group equipment consists of such basic elements as a headstock and tailstock, a support, a device apron, a gearbox for changing speeds, a feedbox, an equipment spindle and a drive motor.

Headstock Tailstock Caliper
Drive shafts Gear shift lever Limb

How the bed and headstock of the machine are arranged

The frame is a supporting element on which all other structural elements of the unit are installed and fixed. Structurally, the frame consists of two walls connected to each other by transverse elements that give it the required level of rigidity. Individual parts of the machine must move along the bed; for this purpose, it is equipped with special guides, three of which have a prismatic section, and one has a flat section. The tailstock of the machine is located on the right side of the bed, along which it moves thanks to internal guides.

The headstock simultaneously performs two functions: it gives the workpiece rotation and supports it during processing. On the front part of this part (it is also called the “spindle head”) there are gearbox control handles. With the help of such handles, the machine spindle is given the required rotation speed.

In order to simplify the control of the gearbox, next to the shift knob there is a plate with a diagram that indicates how to position the handle so that the spindle rotates at the required frequency.

Speed ​​selection lever for BF20 Yario machine

In addition to the gearbox, the headstock of the machine also contains a spindle rotation unit, in which rolling or sliding bearings can be used. The device chuck (cam or drive type) is fixed at the end of the spindle using a threaded connection. It is this unit that is responsible for transmitting rotation to the workpiece during its processing.

The frame guides along which the machine carriage moves (the lower part of the support) have a prismatic cross-section. They are subject to high demands on parallelism and straightness. If these requirements are neglected, it will be impossible to ensure high quality processing.

Purpose of the tailstock of turning equipment

The design, which can include several design options, is necessary not only for fixing parts of considerable length, but also for fastening various tools: drills, taps, reamers, etc. The additional center of the machine, which is installed on the tailstock, can be rotating or stationary.

A scheme with a rotating rear center is used if the equipment is used for high-speed processing of parts, as well as when removing chips that have a large cross-section. When implementing this scheme, the tailstock is made with the following design: two bearings are installed in the quill hole - a front thrust bearing (with tapered rollers) and a rear radial one - as well as a bushing, the inner part of which is bored to a cone.

Axial loads arising during processing of a part are absorbed by a thrust ball bearing. Installation and fixation of the rear center of the equipment is ensured by the tapered hole of the bushing. If it is necessary to install a drill or other axial tool in such a center, the sleeve can be rigidly fixed with a stopper, which will prevent it from rotating with the tool.

The tailstock, the center of which does not rotate, is fixed to a plate that moves along the guides of the machine. The quill installed in such a headstock moves along the hole in it using a special nut. In the front part of the quill itself, into which the center of the machine or the shank of the axial tool is installed, a conical hole is made. The movement of the nut and, accordingly, the quill is ensured by the rotation of a special flywheel connected to the screw. What is important is that the quill can also move in the transverse direction; without such movement it is impossible to process parts with a flat cone.

Spindle as an element of a lathe

The most important structural component of a lathe is its spindle, which is a hollow metal shaft with a conical inner hole. What is noteworthy is that several structural elements of the machine are responsible for the correct functioning of this unit. It is in the inner conical hole of the spindle that various tools, mandrels and other devices are fixed.

In order to be able to install a faceplate or a lathe chuck on the spindle, its design includes a thread, and to center the latter there is also a collar on the neck. In addition, to prevent spontaneous unscrewing of the chuck when the spindle is quickly stopped, some models of lathes are equipped with a special groove.

The results of machining parts made of metal and other materials on the machine largely depend on the quality of manufacturing and assembly of all elements of the spindle assembly. In the elements of this unit, in which both the workpiece and the tool can be fixed, there should not be even the slightest play that causes vibration during the rotational movement. This must be carefully monitored both during the operation of the unit and when purchasing it.

In spindle units, which can be immediately determined from their drawing, sliding or rolling bearings can be installed - with roller or ball elements. Of course, rolling bearings provide greater rigidity and accuracy; they are installed on devices that process workpieces at high speeds and with significant loads.

Caliper structure

A lathe support is a unit that ensures the fixation of the cutting tool, as well as its movement in the inclined, longitudinal and transverse directions. It is on the support that the tool holder is located, moving with it due to a manual or mechanical drive.

The movement of this unit is ensured by its structure, which is characteristic of all lathes.

• The longitudinal movement, for which the lead screw is responsible, is performed by the caliper carriage, while it moves along the longitudinal guides of the frame.
• Transverse movement is performed by the upper - rotating - part of the support, on which the tool holder is installed (such movement, due to which the depth of processing can be adjusted, is carried out along the transverse guides of the support itself, which are shaped like a dovetail).

The tool holder, also called the cutting head, is installed on the top of the support. The latter can be fixed at different angles using special nuts. Depending on the need, single or multiple tool holders can be installed on lathes. The body of a typical cutting head has a cylindrical shape, and the tool is inserted into a special side slot in it and secured with bolts. There is a protrusion on the bottom of the cutting head that fits into a corresponding slot on the support. This is the most typical tool holder mounting scheme, used primarily on machines designed to perform simple turning work.

Electrical part of a lathe

All modern turning machines, which are characterized by a fairly high complexity of their design, are driven by a drive, which uses electric motors of various powers. Electric motors installed on such units can be asynchronous or powered by direct current. Depending on the model, the engine can produce one or more rotation speeds.

Electrical diagram of a 1K62 lathe (click to enlarge)

Let's look at the design of a lathe. As an example, let’s take a screw-cutting lathe, model 1K62, which is common in production. The figure shows a diagram of the device of a screw-cutting lathe.

Fig. 1 - headstock with gearbox, 2 - replacement wheels, 3 - feed box, 4 - bed, 5 - apron, 6 - caliper, 7 - tailstock, 8 - cabinet with electrical equipment.

To study the structure of a lathe, consider the main elements according to the diagram:

Headstock 1- cast iron box, main working body - spindle and gearbox. It serves to secure the workpiece and transmit to it the main movement - rotation. The most important part of the headstock is the spindle, which is a hollow steel shaft. At the front end of the spindle there is a precise thread cut onto which a jaw or driver chuck or faceplate can be screwed. At the same end of the spindle there is a conical hole into which the front center can be inserted.

Guitar 2— necessary for adjusting the feed or pitch of the machine thread being cut by installing the corresponding replaceable gears. Mostly not used in modern machines.

Feed box 3- this is a machine unit that transmits rotation from the spindle to the lead screw or lead shaft. With its help, the speed of rotation of the lead screw and the drive shaft changes, which achieves the movement of the caliper at the selected speed in the longitudinal and transverse directions

Stanina 4— cast iron base, where the main mechanisms of the machine are located. The upper part of the frame consists of two prismatic and two flat guides along which the tailstock and caliper move. The bed is fixed on two pedestals.

Apron 5- used to convert the rotational movement of the drive shaft into longitudinal or transverse movement of the caliper.

Caliper 6— designed to move the tool holder with the cutter in the longitudinal, transverse and inclined directions to the machine axis. The cutter can be given movement along and across the bed both mechanically and manually.

The support consists of a carriage that moves along the guides of the frame, an apron in which the mechanism for converting the rotational movement of the running shaft and lead screw into the rectilinear movement of the support port is located, a transverse slide mechanism, a cutting (upper) slide mechanism, a mechanism tool holder.

Tailstock 7— necessary for installing the end of long workpieces during processing, as well as for securing and feeding core tools (drills, countersinks, reamers).

Cabinet with electrical equipment 8 — Starting the electric motor, starting and stopping the machine, monitoring the operation of the gearbox and feed box, monitoring the apron mechanism, etc. are carried out by the corresponding controls (handles, buttons, handwheels). Also, additionally, the lathe can be used on the machine: chucks, faceplates, collets, centers, clamps, steady rests, mandrels (for securing workpieces).

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Lathes have been known since ancient times. Machine tools of that time, as can be seen from Fig. 20 were very primitive. The support was not yet known, so the cutter had to be held by hand while working, and the rotation of the workpiece was also conveyed manually using a rope. It is clear that working on such a machine required a lot of physical strength and could not be productive.

In 1712, for the first time in the world, Russian mechanic Andrei Konstantinovich Nartov created a lathe with a mechanically driven support.

The invention of the caliper by A.K. Nartov freed the turner’s hands from the need to hold the cutter while turning the part and marked the beginning of a new era in the development of not only lathes, but also other metal-cutting machines.

A. Nartov made his lathe with a support 70 years earlier than the Englishman Maudsley, to whom the invention of the support is incorrectly attributed in the West, and was 70 years ahead of Western Europe and America.

After Nartov, the production of lathes was especially widely developed at the Tula and other arms factories. One of these machines is shown in Fig. 21. The supports 2 of these machines were moved mechanically using gears 1 and a screw 3 with a nut.

The lathe shown in Fig. 22, manufactured in the middle of the last century, is closer in design to modern machines. He has headstock with stepped pulley 1, which allows you to change the speed of the workpieces. The support 2 is moved using lead screw 3, a nut installed in the apron, and replaceable gears 4.

Later, on lathes with step-pulley drives, they began to use feed boxes; in addition to the lead screw, they began to use drive shaft. At the beginning of the 20th century. With the invention of high-speed steel, high-speed powerful lathes appear, in which the spindle speed is changed using gears enclosed in gearbox.

Thus, modern lathes have speed boxes for changing the number of revolutions of the workpiece and a feed box for changing the feed rate.

In Fig. 23 shows the names of the main components and parts of a screw-cutting lathe.

The bed is a support for the headstock and tailstock, and also serves to move the caliper and tailstock along it.

The headstock serves to support the workpiece and transmit rotation to it.

The tailstock serves to support the other end of the workpiece; also used for installing drills, reamer, taps and other tools.

The support is designed to move the cutter fixed in the tool holder in the longitudinal, transverse and inclined directions to the machine axis.

The feed box is designed to transmit rotation to the lead screw or lead shaft, as well as to change the number of their revolutions. The lead screw is used to transmit motion from the feed box to the caliper carriage only when cutting threads, and the lead shaft is used when performing all basic turning operations.

The apron serves to convert the rotational movement of the drive shaft into longitudinal or transverse movement of the caliper.

2. Bed

All components of the lathe are mounted on a bed standing on two pedestals (legs).

The bed (Fig. 24) consists of two longitudinal walls 2 and 8, connected for greater rigidity by transverse ribs 1, and has four guides, three of which are prismatic 3

and one flat 4. At the left end of the frame 5 is attached headstock, - and on the other, on the inner pair of guides, they install tailstock. The tailstock can be moved along guides along the bed and secured in the required position. The lower plate of the support, called the carriage, moves along the two outer prismatic guides of the frame. The bed guides must be accurately machined along the working planes. In addition, the guides must be strictly straight and mutually parallel, since the accuracy of the processing of parts depends on this.

3. Headstock

The headstock is the part of the lathe that serves to support the workpiece and cause it to rotate. In the headstock housing, a spindle rotates in sliding or rolling bearings, which transmits the rotation of the workpiece using a cam or drive chuck screwed onto the right end of the threaded spindle.

On the outer wall of the headstock housing there are gearbox handles (see Fig. 23), which are used to switch the spindle speed. How to turn these handles to obtain the required number of spindle revolutions per minute is indicated on a metal plate attached to the outer wall of the headstock.

To protect the gears of the gearbox from premature wear, switching the handles should be done only after turning off the spindle, when its speed is low.

4. Spindle

Spindle design. The spindle (Fig. 25, a) is the most critical part of the lathe. It is a steel hollow shaft 1, into the conical hole of which the front center 5 is inserted, as well as various mandrels, devices, etc. The through hole 7 in the spindle is used to pass the bar when performing bar work, as well as to knock out the front center.

At the front end of the spindle there is a precise thread 4 cut onto which a cartridge or faceplate can be screwed, and behind the thread there is a neck 6 with a collar 3 for centering the cartridge; The 1A62 machine, in addition, has a groove 2 for chuck guards, which prevents it from spontaneously collapsing during rapid braking of the spindle.

The spindle rotates in the headstock bearings and transmits the rotation of the workpiece. In lathes, spindles usually rotate in plain bearings, but high-speed spindles rotate in rolling bearings (ball and roller), which have higher rigidity than plain bearings.

One of the main conditions for precise processing of parts on lathes is the correct rotation of the spindle. It is necessary that the spindle, under the influence of a load, should not have any play in the bearings - neither in the axial nor in the radial directions - and at the same time rotate evenly and easily. The presence of slack between the spindle and bearings causes spindle runout, and this in turn leads to inaccurate processing, vibration of the cutter and the workpiece. Spindle stability is ensured by the use of a new type of massive adjustable rolling bearings.

Front spindle bearing. In Fig. 25, c shows the design of the front (right) bearing of the lathe spindle. The conical neck 8 of the spindle rotates in a double-row roller bearing 9, which receives forced lubrication from a special pump located in the gearbox. The inner conical ring 10 of the roller bearing is bored along the spindle journal.

When adjusting the bearing, loosen the locking screw 11 and turn the nut 12, due to which the ring 10 moves along the axis. In this case, due to the taper of the neck 8, the gap between it and the conical ring changes. When turning nut 12 to the right, the bearing is tightened, and when turning to the left, it is loosened. The movement of the ring 10 is carried out so that the spindle with the chuck can be turned manually. After adjustment, tighten the locking screw 11, which protects the nut 12 from unscrewing.

Rear spindle bearing. The rear spindle bearing is loaded significantly less than the front one. Its main purpose is to perceive forces acting on the spindle in the axial direction.

The rear journal of the spindle usually rotates in a tapered roller bearing 14 (Fig. 25, b). The axial force acting on the spindle from right to left is perceived by a thrust ball bearing 13 located at the rear support of the spindle. If the axial force is directed from left to right, trying to pull the spindle out of the gearbox, it is perceived by the tapered roller bearing 14. This bearing also serves as a support in the transverse direction for the rear end of the spindle. It is adjusted using nut 15 in the same way as the front bearing.

5. Tailstock

The tailstock serves to support the right end of long parts when processing them in the centers. In some cases, it is also used to install drills, reamers, taps and other tools.

Tailstock with regular center. Tailstock housing 1 (Fig. 26, a) is located on plate 9 lying on the frame guides. A quill 6 with a nut 7 fixed in it can move longitudinally in the housing hole. At the front end, the quill is equipped with a conical hole into which the center 3 and sometimes the tail part of a drill, countersink or reamer is inserted. The quill 6 is moved by means of a handwheel 8 that rotates a screw 5; When rotating, the screw moves nut 7, and with it the quill. Handle 4 serves to firmly secure the quill in the headstock body. By means of screws 10, it is possible to shift the body 1 relative to the plate 9 in the transverse direction and thereby shift the axis of the tailstock quill relative to the axis of the spindle. This is sometimes resorted to when turning flat cones.

To turn the centers of parts of different lengths, plate 9 is moved along with the tailstock body along the bed and secured in the desired position. The headstock is secured to the frame using clamping bolts or using an eccentric clamp and bracket 11. Using handle 2, turn the eccentric roller and release or tighten bracket 11. Having released the bracket, move the tailstock and, having installed it in the desired position, tighten the bracket again.

To remove the rear center from the conical socket of the quill, turn the handwheel 8 so as to pull the quill into the tailstock body as far as it will go. In the extreme position, the end of screw 5 pushes out center 3.

Tailstock with built-in rotating center. In lathes for high-speed cutting, tailstocks with a built-in rotating center are used. In Fig. 26, b shows one of the designs of such a tailstock.

In the front part of the quill 5 there is a hole into which the bearing 3 with tapered rollers, the front thrust ball bearing 4 and the rear ball bearing 6 for the sleeve 2 are pressed. This sleeve has a conical hole into which the center 1 is inserted. The axial force is absorbed by the thrust ball bearing 6. If you connect bushing 2 with quill 5 using a stopper, the bushing will not rotate. In this case, you can install a drill or other centering tool (countersink, reamer) in the tailstock.

6. Feed mechanism

The mechanism for transmitting movement from the spindle to the support (Fig. 27) consists of: bit I, designed to change the direction of feed; guitars II with replaceable gears, which makes it possible, together with the feed box, to receive various feeds (large and small); feed boxes III; lead screw 1; drive shaft 2; apron IV, in which mechanisms are located that convert the rotational movement of the lead shaft and lead screw into the translational movement of the cutter.

Not all machines have all the listed mechanisms. For example, in machines designed exclusively for cutting precise threads, there is no feed box; the feeds here are changed by changing the gears on the guitar. On the other hand, on some machines the feed unit has two reversing mechanisms: one serves only to change the direction of rotation of the lead screw (which is required, for example, to switch from cutting right-hand threads to cutting left-hand threads), and the other changes the direction of rotation of the lead shaft, changing thus the direction of longitudinal or transverse feed.

Snaffle bit. In Fig. 28 shows a snaffle that was widely used in older types of screw-cutting lathes. A gear 1 is attached to the end of the spindle, with which, using lever A, either wheel 4 or wheel 2 can be engaged. Gear 2 is constantly engaged with wheel 4 and wheel 3. If, by turning lever A down, wheel 1 is engaged with wheel 4, then the rotation of wheel 3 will be transmitted through two intermediate wheels 4 and 2 (Fig. 28, c). By turning lever A upward (Fig. 28, a), we engage wheel 1 directly with wheel 2. In the latter case, wheel 5 will receive rotation only through one intermediate wheel, therefore, it will rotate in a different direction than in the first case. If lever A is fixed in the middle position, as shown in Fig. 28, 6, then gears 4 and 2 do not engage with wheel 1 and the feed mechanism will be turned off.

In Fig. 29, b. another design of a reversing mechanism made of cylindrical wheels is shown. On drive shaft I a block of two wheels 1 and 3 sits freely to communicate forward motion to driven shaft II and wheel 5 for reverse motion. Wheels 1, 3 and 5 can be rigidly connected to shaft I using a plate-type friction clutch M.

On the driven shaft II there is a movable block consisting of wheels 2 and 4 on the left, and wheel 6, rigidly fixed to the key, on the right.

Feed box. Most modern screw-cutting lathes have feed boxes; they serve to quickly switch the rotation speed of the lead screw and the lead shaft, i.e., to change the feed. Replaceable wheels on these machines are used only when the required feed cannot be achieved by switching the feed box handles.

There are many different feedbox systems. A very common type is the feed box, which uses ring gear mechanism(Fig. 30).

The first roller 7 of the feed box receives rotation from the replacement wheels of the guitar. This roller has a long keyway 6, in which the key of the gear 3 located in the lever 2 slides. Lever 2 carries an axis 5, on which the ring wheel 4 rotates freely, constantly engaged with wheel 3. By means of lever 2, wheel 3 together with wheel 4 can be moved along roller 7; By turning lever 2, you can engage the rim wheel 4 with any of the ten wheels of the toothed cone 8, mounted on the roller 9.

Lever 2 can have ten positions according to the number of wheels of the gear cone 8. In each of these positions, the lever is held by a pin 1 entering one of the holes in the front wall 15 of the feed box.

When the lever 2 is moved, due to the adhesion of the wheel 4 with the various wheels of the gear cone 8, the rotation speed of the roller 9 changes. At the right end of this roller, on a sliding key, there is a wheel 10, which has a number of protrusions on the right end. In the left position, wheel 10 is engaged with wheel 14, mounted on the running shaft 13. If the wheel 10 is shifted to the right, along the shaft 9, it will disengage with the wheel 14 and the end protrusions will engage with the cam clutch 11, which is rigidly seated on the lead screw 12. In this case, shaft 9 will be directly connected to the lead screw 12. When the lead screw is turned on, the lead shaft 13 remains stationary; on the contrary, when the drive shaft is turned on, the lead screw remains motionless.

On the wall of the feed box there is usually a sign indicating which feeds or which thread pitches are obtained for each of the ten positions of lever 2 with a certain selection of guitar wheels.

7. Caliper

The lathe support (Fig. 31) is designed to move the tool holder with the cutter in the longitudinal, transverse and inclined directions to the machine axis. The cutter can be given movement along and across the bed both mechanically and manually.

The lower plate 1 of the caliper, called carriage or longitudinal slides, moves along the bed guides mechanically or manually, and the cutter moves in the longitudinal direction. On the upper surface of the carriage 1 there are transverse guides 12 in the shape of a dovetail, located perpendicular to the frame guides. The lower transverse part 3 moves on the guides 12 - cross slide supports, through which the cutter receives movement perpendicular to the axis of the spindle.

On the upper surface of the cross slide 3 there is turning part 4 calipers. By unscrewing the nuts 10, you can rotate this part of the caliper at the desired angle relative to the frame guides, after which the nuts 10 need to be tightened.

On the upper surface of the turning part there are guides 5 in the shape of a dovetail, along which, when the handle 13 rotates, the upper part 11 moves - upper caliper slide.

Caliper adjustment. After a certain period of operation of the machine, when a gap appears on the side surfaces of the dovetail, the accuracy of the machine operation decreases. To reduce this gap to a normal value, it is necessary to tighten the wedge strip available for this purpose (not shown in Fig. 31).

The excess gap that occurs after a certain period of work between the nut and the transverse lead screw should also be reduced to a normal value.

As can be seen from Fig. 32, the nut covering the transverse screw 1 consists of two halves 2 and 7. To reduce the gap between the nut and the screw to a normal value, the following must be done. Lightly unscrew screws 3 and 6, with which both halves of the nut are screwed to the bottom of the caliper, then use screw 5 to move the one-sided wedge 4 upward, while both halves of the nut move apart and the gap between the transverse screw and the nut decreases. After adjusting the gap, you need to tighten the screws again. 3 and 6, securing both halves of the nut.

Tool holders. A tool holder is installed on the upper part of the caliper to secure the cutters. Tool holders come in various designs.

On light machines, a single tool holder is used (Fig. 33, a). It is a cylindrical body 1, into the slot of which a cutter is inserted and secured with a bolt 2. The cutter rests on a lining 3, the lower spherical surface of which is in contact with the same surface of the ring 4. This device allows you to tilt the lining with the cutter and set its cutting edge to the height of the centers . The lower part 5 of the tool holder, which has a T-shape, is inserted into the groove in the upper part of the caliper. Fastening the cutter in a tool holder of this type is quick, but not strong enough, so this tool holder is used mainly for small jobs.

The cutter is fixed more firmly in the tool holder shown in Fig. 33, b. The tool holder 5, equipped with a T-shaped block 1, is fixed on the upper part of the support with a nut 4. To adjust the position of the cutting edge of the tool in height, the tool holder has a lining 2, the lower spherical surface of which rests on the same surface of the tool holder block. The cutter is secured with two bolts 3. A tool holder of this type is used on both small and large machines.

On large lathes, single tool holders are used (Fig. 33, b). In this case, the cutter is installed on plane 7 of the upper part of the caliper and secured with strap 2, tightening nut 4. To protect bolt 3 from bending, strap 2 is supported by a screw resting on shoe 6. When unscrewing nut 4, spring 1 lifts strap 2.

Most often, tetrahedral rotary cutting heads are used on medium-sized screw-cutting lathes (see Fig. 31).

The cutting head (tool holder) 6 is installed on the upper part of the support 11; Four cutters can be secured in the tool holder with screws 8 at the same time. You can work with any of the installed cutters. To do this, you need to turn the head and put the required cutter in the working position. Before turning the head, it is necessary to unfasten it by turning handle 9, connected to the nut sitting on screw 7. After each turn, the head must be clamped again using the same handle 9.

8. Apron

An apron 17 is attached to the bottom surface of carriage 1 (see Fig. 31) - this is the name of the part of the machine that contains mechanisms for longitudinal and transverse movements of the cutter (feed) and feed control mechanisms. These movements can be done manually or mechanically.

The transverse feed of the cutter is made by moving the lower part 3 of the caliper. To do this, handle 14 rotates the screw, the nut of which is fastened to the lower part of the caliper.

Handwheel 16 is used to manually communicate longitudinal feed to the caliper along the bed guides. For more precise mechanical movement of the caliper, a lead screw is used (Fig. 34). Screw 1 is driven by the feed box. A split nut 2 and 8 moves along it, installed in the caliper apron and called uterine. When cutting a thread with a cutter, both halves of the nut 2 and 8 are brought together using handle 5; they capture the thread of screw 1 so that when it rotates, the apron, and with it the caliper, receive longitudinal movement.

The mechanism for sliding and spreading the halves of the split nut is designed as follows. On the handle shaft 5 (Fig. 34) there is a disk 4 with two spiral slots 6, into which the fingers 7 of the lower 8 and upper 2 halves of the nut fit. When the disk is turned, 4 slots force the fingers, and therefore the halves of the nut, to move closer together or diverge. The nut halves slide along dovetail-shaped guides 3 of the apron.

In all turning operations, except for cutting threads with a cutter, longitudinal feed is carried out using a gear rack rigidly attached to the frame and a gear rolling along it installed in the apron (see Fig. 36 a). This wheel is rotated either manually or by the drive shaft.

On a lathe, you cannot turn on the longitudinal feed mechanism from the running shaft at the same time as closing the nut on the lead screw: this leads to inevitable breakdown of the apron mechanism or feed box.

To prevent such misoperations, the machine has a special mechanism called a locking mechanism.

Control questions 1. Name the main components and parts of a lathe.
2. How is the lathe bed constructed and what is its purpose?
3. What is the purpose of the headstock of a lathe?
4. What main parts and mechanisms does the headstock consist of?
5. What is the machine’s gearbox used for?
6 How does the spindle work and what is its purpose?
7. Tell us about the structure of spindle bearings (Fig. 25).
8. Tell us about the structure and purpose of the tailstock on a lathe.
9. Through what mechanisms is motion transmitted from the spindle to the machine support?
10. How does the bit work?
11. What is the purpose of the feed box?
12. What are the main parts of the caliper?
13. What mechanisms are contained in the machine apron?
14. How is motion transmitted from the drive shaft to the machine support?

The tailstock of a lathe is designed to support the workpiece being processed, which is attached directly to this unit. the workpiece rotates about its axis while it is being processed by a cutting tool. You can also attach the tools themselves to the devices, such as countersinks, drills, taps, dies, centers, reamers, and so on. It is located on the frame, and the position of the center in this case depends on the exact sequence in which the bolts are fastened. During the adjustment process, you should avoid blows to the body, as they can disturb the center position. Therefore, problems may arise regarding how to position the tailstock. This technical unit of the machine is moved manually, as it moves along the guides of the frame. Fastening operations are carried out using a handle.

photo: tailstock of lathe

The machine itself, as well as other models, is used for processing parts such as shafts, disks, bushings and other cylindrical workpieces. They are processed by turning, which takes place inside and outside the part, depending on the cutter used. This equipment is very common in modern industry, so all its components are precisely calibrated.

This element of the lathe has the following main structural details:

• Device base or plate;
• Tailstock housing
• Pinol;
• Flywheel (quill movement wheel);
• Flywheel handle (tailstock fixation);
• Screw for transverse movement of the tailstock.

photo: tailstock device of a lathe

As a rule, the slab in all models is made flat. During operation, ensure maximum secure fastening. The protrusion of the cross member must be located in the slot formed by the machine guides.

Working principle of the tailstock

The tailstock of a lathe has a hole in the quill where machining tools are inserted. During operation, it moves along the bed to select the appropriate distance corresponding to the size of the workpiece being processed. Depending on the type of work, both rotating and stationary parts are placed in the tailstock. All movements are carried out during the preparatory processes, while during operation this unit remains motionless.

Basic movements

The tailstock of the lathe moves when the protrusion of the bars engages. At the same time, automatic movement of the caliper may be activated.

The tailstock is moved along the bed using a special handle. This can be used to position the workpiece in the center of the device, to bring the cutter to the part, and also to rotate the turret. If the machine is of medium size, then the movement occurs due to the rotation of a small gear, which is located in the bracket. It engages with the lathe of the machine. If the size of the machine is large, then this procedure is carried out using an electric drive.

The quill moves in the axial direction. The feed movement here also occurs using axial movement. There is no difference here whether the cutting tool or the workpiece being processed is fixed in the quill, since the rotational movements are determined by the operations performed on the machine.

Tailstock alignment and adjustment

Before inserting the part into the tailstock, it should be adjusted. First of all, you need to determine the alignment. To do this, the tailstock of the 1K62 lathe is brought to the top of the opposite unit so that the distance between them is no more than 0.5 mm. After this, you need to secure the quill and check, perhaps by eye, how much the vertices coincide on the horizontal plane. If they do not match, then the alignment is adjusted by moving the rear tank.

Another adjustment method involves clamping the workpiece in the cams and then grinding it along the diameter, which should coincide with the diameter of the tailstock quill. Measurements here are made with a micrometer. On the quill itself and on the groove, the indicator is set to the zero position. To avoid play during adjustment, everything must be securely clamped. The part should also be pressed at the centers with the same force. This test grinding allows you to adjust the tailstock for serial work with a batch of parts and achieve accuracy up to several hundredths of millimeters of error.

Tailstock repair

Repairing a 16K20 tailstock often involves restoring the accuracy of the mating surface of the body, frame and bridge, as well as setting the correct centers and restoring the accuracy of the holes in the body. Restoring the holes that are intended for the quill is one of the most labor-intensive operations. They are repaired using lapping, as well as boring, which requires subsequent finishing with acrylic layers. For slightly worn holes, ordinary lapping is suitable, and the centers are restored using compensation pads.

When repairing tailstock quills, operations are used to grind the surface of the outer diameter. To restore the conical hole, use a compensation sleeve. This product has a cylindrical shape on the outside and a conical shape on the inside. It is often made from alloy steel and then hardened. The outer diameter of the bushing should be made according to the boring hole and at the same time have a small gap, approximately 0.05 mm.

The bearing holes on the housing often have to be repaired. Repair is carried out by replacing the housings of the worn-out unit. After this, you need to adjust the internal diameter to the existing bearings, and also check the radial runout.

Construction of lathes

TO category:

Turning

Construction of lathes

Basic information about the kinematics of lathes. Kinematic communication in lathes is carried out through gears, with the help of which rotational motion from one shaft (Fig. 49) is transferred to another II or rotational motion is converted into translational motion. The simplest transmission is a belt transmission, which can be flat-belt (Fig. 49, a) or V-belt (Fig. 49, b), in addition, the transmission can be gear (Fig. 49, c) and chain (Fig. 49, d) . In gearboxes, gears are mainly used: cylindrical (Fig. 50, a), bevel (Fig. 50.6), worm (Fig. 50, c), screw (Fig. 50, d), rack and pinion (Fig. 50 ) and ball roller (Fig. 50, e) in the guide units. The use of gears in a lathe is shown in Fig. 51.

Rice. 50. Types of gears in gearboxes

Rice. 51. Gears used in the toning mill

Rice. 52. Different types of gears

Rice. 53. Kinematic pair

Kinematic pair - a connection of two contacting links, allowing their relative movement, for example, the transfer of movement from / to shaft II (Fig. 53, a) or the transformation of one movement A into another B (Fig. 53, b).

Rice. 54. Changing the direction of rotation in the assemblies of a lathe

Rice. 55. Kinematic chain

Rice. 56. Kinematic chain with an even (a) and odd (b) number of gears

Rice. 57. Kinematic chain of speed control of a tone-screw-cutting machine

Rice. 58. Main components of a tone-screw-cutting machine

Rice. 59. Front woman

Rice. 60. Spindle assembly with supports

An example of a kinematic chain is shown in Fig. 55. The sign of the gear ratio of the kinematic chain is positive if the direction of rotation of the final and initial links of the chain is the same, and negative if the directions of their rotation are different.

A positive sign of the gear ratio of the kinematic chain is ensured if the kinematic chain consists of an even number of gears (Fig. 56, a), and a negative sign if the number of gears is odd (Fig. 56.6).

The kinematic chain of a machine is a set of interconnected kinematic pairs that transmit motion from the source of motion to the final link - the working body of the machine spindle (Fig. 57).

Main components of the machine. The main components of a screw-cutting lathe are: bed (Fig. 58), headstock (gearbox), tailstock, feedbox, apron and caliper.

Rice. 61. Methods for attaching a tone cartridge to a spindle

Rice. 62. Tailstock

Rice. 63. Caliper

Rice. 64. Fartun and its knots

Rice. 66. Transverse (a) and upper (b) slides

Rice. 67. Limbo

Rice. 68. Tool holders

The headstock (Fig. 59) consists of a spindle assembly with supports (Fig. 60) and serves to transmit rotation of the workpiece fixed in the chuck by means of a conical (Fig. 61, a) or threaded (Fig. 61, b) connection on the chuck flange .

The tailstock serves to center the second end of the workpiece or tool and consists of a base (Fig. 62), a body, a quill, a handwheel, a handle for attaching the tailstock to the frame and a quill clamp handle. At the front end of the quill there is a conical socket into which a center or cutting tool (drill, countersink, reamer, etc.) is inserted.

The support is designed to fasten and move the cutter during the cutting process (Fig. 63). The cutter is secured in a cutter holder mounted on the upper slide. The caliper can be moved manually by means of a gear (Fig. 64) and rack, as well as mechanically by means of a drive shaft. The mechanical movement of the caliper when cutting threads is carried out using a lead screw and a detachable (uterine) nut (Fig. 65).

The cross slide is used to move the cutter towards the workpiece (Fig. 66, a). The upper slides are installed on them (Fig. 66, b). The cutter is fed both in the transverse and longitudinal directions by flywheels with dials for setting to the required processing size (Fig. 67).

Rice. 69. Feed box

Rice. 70. Transmission of motion from the spindle to the chassis

Rice. 71. Drive of a lathe to a screw (a) with right (b) and left (c) rotation of the lead screw

Rice. 72. Controls of tone-screw-cutting machine 16K20

Tool holders are designed for attaching cutters to the machine. In a single tool holder (Fig. 68, a), the cutter is secured with one screw. A more reliable fastening of the cutter is provided by the cutter holder (Fig. 68, b), in which the cutter is secured with two screws. On universal machines, four-place tool holders are used (Fig. 68, c), allowing the simultaneous installation of four cutters.

The feed box, providing movement of the drive shaft or screw (Fig. 69), allows you to change their rotation speed (Fig. 70) by switching gear blocks using levers and handles.

The lathe drive consists of an electric motor (Fig. 71) and a motion transmission mechanism. The location and purpose of the controls of the 16K20 screw-cutting lathe are shown in Fig. 72: 1 - control handle for the friction clutch of the main drive; 2 - variator for thread pitch feed and disabling the feed mechanism; 3-variable feed and type of thread being cut; 4 - thread pitch feed variator; 5 - switch for left or right thread; 6 - handle for setting normal or increased thread pitch and position when dividing the thread into starts (multi-start); 7 and 8 - handles for setting the spindle speed;

Rice. 73. Three-jaw self-centering chuck with reverse (a) and direct (b) zeros

Rice. 74. Spiral three-jaw self-centering chuck: 1-drive gear; 2-disc; 3-jaw lathe chuck; 4-tooth rim

Rice. 75. Chucks with eccentric (a), screw (b) and rack and pinion (c) drive

Devices and auxiliary tools of lathes are designed for installation and fastening of workpieces and tools. The most widely used lathe chucks, centers, mandrels, steady rests, faceplates, adapter bushings and clamps.

Lathe chucks are designed to hold workpieces or tools in them. Self-centering three-jaw chucks (Fig. 73) are designed for installation and fastening of symmetrical workpieces. They are the most convenient to use and do not require much time to install and secure the workpiece. To move the jaws in the chuck, discs with a spiral groove are used (Fig. 74). A chuck with eccentric jaw clamping is shown in Fig. 75, a. Screw (Fig. 75, b) and rack and pinion (Fig. 75, c) drives are also used for movement. In the latter, when the screw rotates, the rack moves the wheel, through which other racks with cams move. In Fig. Fig. 76 shows a two-jaw chuck with a screw drive (Fig. 76, a) and a self-clamping chuck with grooved jaws (Fig. 76, b), and in Fig. 77 - pneumatic cartridge.

Rice. 76. Two-jaw chuck with a screw drive (a) and a self-clamping chuck with grooved nulches (b): 1-body; 2-grooved cams; 3-focus; 4-cover

Rice. 77. Pneumatic chuck: 1-rod; 2-rod; 3.4-slider with conical bushing; 5-two-arm lever; 6,7-auxiliary and main clamping jaws

Rice. 78. Four-jaw non-self-centering chuck (a) and faceplate (b): 1 - T-shaped guide grooves; 2 - through grooves

Rice. 79. Collet chuck: a - for processing with low precision; b - for processing with increased accuracy

Rice. 80. Roller self-clamping chuck

For fastening asymmetrical workpieces, four-jaw non-self-centering chucks are used (Fig. 78, a). In this chuck, the clamping jaws move independently of each other. Faceplates are also used to fasten asymmetrical workpieces (Fig. 78.6).

Rice. 81. Drive cartridge with a bent collar (a) and with a safety casing (b)

Rice. 82. Self-centering drill chuck

Rice. 83. Turning centers: L-center length; I - seat length

To fasten workpieces of small diameters, collet and roller self-clamping chucks are used. The collet chuck (Fig. 79) consists of a collet and a body. Each collet has a specific hole diameter. When switching to processing a workpiece of a different diameter, the collet is changed. In a roller self-clamping chuck (Fig. 80), the workpieces are secured with three rollers, which, rolling over surfaces A, B, C, are wedged between these surfaces and the workpiece.

When processing workpieces in centers, driving chucks are used (Fig. 81). To fasten drills and other end tools, self-centering drill chucks are used (Fig. 82).

Centers. Turning centers (Fig. 83) are used to secure workpieces on the machine. The center has a working part (Fig. 84), on which the workpiece is attached, and a shank 2 in the form of a cone, with which the center is inserted into the quill. The cylindrical part of the shank is installed in the quill socket. Straight cones (Fig. 84, a) are used to install workpieces with regular (internal) centers. For workpieces with external centers, reverse centers are used (Fig. 84, b), which are used for thin workpieces. When processing the end of a workpiece when working in centers, half-centers are used (Fig. 84, c). When processing conical surfaces with a large slope, it is advisable to use centers with a spherical surface (Fig. 84, d). Workpieces with large center holes or bushing-type parts are secured using corrugated centers (Fig. 84,d). With this fastening method, you can grind the workpiece along its entire length in one installation. When processing precision workpieces at high speeds, straight centers with a tip equipped with a hard alloy are used (Fig. 84, e). For rough work, when working on centers, rotating centers are used (Fig. 84, g). The rotating center is installed in the tailstock quill. When processing workpieces of large diameters, when abundant lubrication of the rubbing surfaces of the centers is necessary, centers with forced supply of lubricant are used (Fig. 84, h). In mass production, when processing workpieces of the same type on semi-automatic machines, floating centers are used (Fig. 84, i). They are installed in the headstock quills.

Rice. 84. Types of tonal centers

Mandrels. For fastening when processing parts such as bushings and obtaining alignment between the internal and external surfaces, various types of mandrels are used. When performing light work, when small layers of metal are cut, conical mandrels are used (Fig. 85, a). The surface of the mandrel is made with a slight taper, which allows the workpiece to be secured to the mandrel. This mandrel can only be used for one base hole. Under difficult working conditions, use the mandrel shown in Fig. 85, b. The workpiece is placed on the cylindrical surface of the mandrel and clamped with a nut through a quick-change washer. The disadvantage of such mandrels is the reduced processing accuracy, since there are gaps between the cylindrically contacting surfaces of the workpiece and the mandrel. To eliminate this drawback, the mandrels shown in Fig. are used. 85, c, d, e. A clamping collet with a cylindrical outer surface is installed on the conical surface of the mandrel, which allows processing workpieces with an accuracy of 6-7 grades. A mandrel with an elastic seating body is also used (Fig. 85, e).

Rice. 85. Mandrels

Rice. 86. Diagram of quick-release clamping mandrels

Rice. 87. Lunettes

Rice. 88. Adapter cones and bushings

Rice. 89. Special bushings-frames

High-speed clamping mandrels with roller (Fig. 86, a, b, c) and cam (Fig. 86, d) clamps are widely used. The workpiece in such mandrels is clamped by moving rollers or cams relative to the clamping profile.

Lunettes. Long and thin workpieces, the length of which is 10-15 times greater than the diameter, bend during processing. The result is an irregularly shaped part. To avoid deflection of the workpiece, fixed (Fig. 87, a, b, d) and movable (Fig. 87, c) steady rests are used. Fixed steady rests are mounted on the guides of the lathe bed. The workpiece is processed on both sides with reinstallation. The movable rests are fixed to the support carriage and move along with the carriage. Unlike a fixed steady rest, which has three supports (cams), a movable steady rest has only two cams, on which the workpiece rests during processing.

Adapter bushings. To mount the tool on the machine, adapter bushings and cones are used (Fig. 88). Adapter bushings are used for fastening drills and other conical tools in the tailstock quill when the dimensions of the tool cone do not correspond to the size of the internal cone of the tailstock quill. Sometimes special mandrel bushings are used, which are fixed in the tool holder (Fig. 89).

Rice. 90. Khomutini

Rice. 91. Drive mandrel

Rice. 92. Physical and mechanical properties of materials used in the manufacture of cutting tools

Clamps (Fig. 90) are designed to transmit rotation to the workpiece when it is processed in the centers. The most common are the clamps shown in Fig. 90, a, b. The clamps are put on the workpiece and secured. The rotation is transmitted through the clamp leash. When processing workpieces of the same type, self-grasping clamps are used (Fig. 90, c, d). In this case, the workpiece is grabbed without the participation of a worker. A safe clamp with a leash is often used (Fig. 90, e). In Fig. 91 shows a driving mandrel, which is also used as clamps to transmit rotation to the workpiece.