If you look at the drawing of any unit designed for turning metals, you can understand that the design and device of the lathe are almost completely identical for different models of installations.
1 Bed and headstock of the turning unit
We can distinguish the following main components of any machine for performing metal turning work - a bed, two headstocks (front and rear), an apron, a caliper, feed and speed boxes, a spindle, an electric motor. All mechanisms and parts of the turning unit are installed in one way or another on the bed. It is this node that represents the base center of the machine.
The frame consists of two longitudinal walls, which are interconnected by transverse ribs that increase the overall rigidity of the installation. The node of interest to us, in addition, has several guides, some of which have a prismatic appearance. The tailstock in turning units is always located on the internal rails. On them, she moves to the required distance during work.
At the left end of the bed, a headstock is installed, which supports the workpiece during processing and gives it rotation.
On the outside, the headstock has handles for another important part of the machine - the gearbox. These handles allow you to select the desired number of revolutions of the spindle assembly during operation. On the plate, which is attached to the headstock (meaning the headstock), there is a schematic drawing indicating exactly how to turn the handle in order to set the required speed. The spindle rotates in rolling or sliding bearings in the headstock housing. At the end of the threaded spindle, a driver or cam-type chuck is put on.
This unit is necessary to transfer the rotation of the part installed on the turning unit for processing. The extreme guide beds (they are prismatic) are strictly verified for their mutual parallelism and straightness. The carriage moves along the guides - the lower part of the caliper. If the machine guides do not meet the requirements above, the parts will be processed poorly.
2 Metal lathe tailstock
This node makes it possible to securely fix extended parts in cases where they are placed in a machining center. In addition, the tailstock is used to attach various working devices (for example, taps, reamers, various types of drills etc.). If the scheme of the headstock is always the same, then the tailstock can be of several varieties. It may have: an ordinary center; built-in rotating center.
The center indicated by the second is placed on those machines on which high-speed processing of the part is planned (a special kinematic scheme is used). The tailstock in this case will have the following design: a machined hole in the quill with tapered rollers and bearings in it. A ball type bearing is needed to install a bushing with a cone-shaped hole. The center is placed in this hole.
The thrust ball bearing takes on the axial force. The sleeve will not be able to rotate when the quill is connected to the sleeve by a specially mounted locking device. If such a kinematic scheme is implemented (it is not difficult to sketch its drawing), the tailstock can serve as a holder for a reamer, drill, any countersink and other center tool.
When the headstock has a normal center, its body is on a plate mounted on rails. A hole is cut out in the body, along which the nut with the quill moves (in the longitudinal direction). The center or shank of any working tool is inserted into a conical hole on the front end of the quill, which is moved with a handwheel. In addition, it is possible to move the quill transversely to the plate using screws. When machining a part with a shallow taper, this possibility is indispensable.
3 Description of lathe spindle
The spindle is a hollow steel shaft with a conical bore. This assembly unit for metal is considered the most important (many other main units of the machine are designed to ensure the operation of the spindle). It has a hole (conical) designed for mounting a variety of tools, mandrels and a front center (the drawing of turning equipment indicates which fixtures can be mounted in the specified hole).
The spindle is threaded. On it you can fix the faceplate on lathe for metal or a cartridge that is centered by means of a shoulder on the neck. On some units, there is also a special groove on the spindle. With a quick stop of the spindle, it eliminates the risk of uncontrolled folding of the chuck. To find out if there is such a groove on a particular lathe, you should carefully study the drawing of the machine, which indicates all its main and additional parts.
The health of the spindle and its correct rotation are key conditions for turning any workpiece. It is important to ensure that this assembly does not have the slightest play or slack in the radial and axial direction in the bearings. In those cases when these negative phenomena occur, the tool holder and the tool in it begin to tremble, which leads to a deterioration in the quality of processing.
On most well-known domestic-made units (for example, on or on), the rotation of the spindle occurs in plain bearings. Although there are equipment with roller and ball bearings, which are considered more rigid and are used for this reason on machines with high speeds for processing workpieces.
4 Metal lathe support
The tool holder with the tool for processing parts installed in it moves thanks to the caliper in an inclined, transverse and longitudinal direction with respect to the axis of the unit. The movement of the working tool is reported on lathes both manually and mechanically. If you look at the drawing of the support of a standard lathe, you can understand how the tool holder with the tool moves:
- in the longitudinal direction - along the longitudinal slide (these parts of the machine are also called the carriage);
- in the transverse direction - along the cross slide (the rotary component of the caliper is mounted on them, which is easy to set at the angle required by the processing conditions using nuts).
Toolholders (cutting heads) are placed on top of the caliper. Structurally, they can be single or multiple. A conventional tool holder is a cylindrical body with a slot. The working tool (turning cutter) is installed in the slot, and then it is fixed with a bolt. From below, the cutting head has the shape of the letter "T", so that it easily enters the groove of the caliper (its upper part). There are other options for mounting the tool holder.
5 Electrical diagram and electric motor of the turning unit
It is clear that no kinematic scheme for the functioning of a machine for turning metal products can be implemented if there is no electric motor on the unit. The engine can be: asynchronous; direct current. The asynchronous type electric motor has a cast iron or aluminum frame, a rotor and a stator. Depending on the model installed on the machine, the engine is capable of delivering several rotation speeds (or one).
Typically, the electrical circuit of lathe equipment is powered by a squirrel-cage motor. The gearbox (as a result, the gearbox and other main electrical components of the machine) in this case is connected to the “engine” either by means of a belt drive or directly to the rotor.
An engine can also be mounted on the turning unit, which allows you to change the speed of rotation according to the stepless principle. It is a device with independent excitation, providing speed control in the range of 10 to 1. Such equipment is used much less frequently, since the squirrel-cage motor is characterized by small dimensions and high level economics of its use.
A DC motor is more often used for the stepless speed control of the spindle assembly mentioned above. The frame of such a motor is made of low-carbon steel grades (the choice of material is not accidental, it is due to the fact that the frame is a magnetic circuit), and the cores of its stator are made of electrical steel. We add that an engine of any kind functions in combination with other electrical equipment, which is mounted on a lathe and ensures its uninterrupted operation according to a certain electrical circuit.
Turning materials consists in the processing of bodies of revolution cutting tool moving along the axis of rotation of the workpiece.At forward movement cutter, a layer of material is removed from the surface of the workpiece.
Historically, the processing of "round" parts was required in almost all industries. National economy. The first lathes were very primitive: the workpiece was rotated using a foot drive, and the cutting tool was held in the hands with emphasis on the stand. On such machines, only soft materials, such as wood, could be processed. 
Lathe of Peter I.
At the end of the 19th century, with the advent of machines, steam and then electric motors began to be used to rotate workpieces. An important achievement of that time was the development and implementation of cutting tool holders. The tool was fixed in a special holder, and the operator could move the holder both parallel and perpendicular to the workpiece by rotating certain handles. Such devices became known as "lathe support".
Lathe, early 20th century.
Modern lathes allow you to automatically move the cutting tool in given directions. The advantages of modern lathes also include the ability to cut threads of almost any profile and a given accuracy. Therefore, modern machines are called "Screw-cutting lathes".
The device and the main components of the lathe.
Most lathes have almost the same design and differ only in size and location of controls. The figure shows a typical lathe and its main components.
lathe axis- virtual axis passing through the axis of rotation of the workpiece parallel to the frame.
Front pedestal and back pedestal- cast iron pedestals, serving as supports for the units and mechanisms of the machine. IN desktop machines cabinets are not used.
bed- the main part, the skeleton of a lathe. The frame is usually made of all-metal by casting from cast iron. The bed is attached to the cabinets of the machine. The large weight of the bed reduces vibrations from the electric drive of the machine and vibrations that occur during the processing of parts. An electric drive motor is installed at the bottom of the bed, inside or behind the lathe.
Electrical cabinet- a cabinet, inside of which there are elements of the electrical circuit of the machine, and on the outer panel there are switches for the main electric motor, a compressor for coolants, a voltmeter and indicator lights.
Headstock- includes a set of gears, levers, shafts and mechanisms for changing the speed of rotation of the workpiece and the feed rate of the cutting tool.
Guitar- an integral part of the headstock, in which interchangeable gears are located for setting the tool drive when threading (in modern machines, gear change is not required).
Spindle- the main shaft of rotation of the workpiece. Mounting devices such as chuck, center, collet and the like can be mounted on the spindle.
Cartridge- the most common fixture for workpieces.
caliper- a device for fastening a processing tool and moving the tool in given directions.
Apron- front caliper cover.
tailstock- a fixture for holding a workpiece (when machining in centers), or for holding tools such as a tap, a die for threading and other devices.
Headstock
On the front surface of the headstock there are levers for switching the spindle speed and the feed rate of the cutting tool.
Nameplates- Explanatory signs. On lathes, on the nameplates, the dependence of the speed of movement or rotation of machine components on the selected positions of the installation handles is indicated.
Spindle speed knobs- depending on the position of these handles, the speed of rotation of the spindle changes. The handles can only be moved when the machine is stopped.
dividing lever- The lever of switching of speed of rotation of a spindle. The lever has three positions. In the leftmost position, the machine spindle rotates at the normal speed set by the spindle speed setting knobs. In the vertical (neutral) position, the spindle does not rotate. In the extreme right position, the spindle rotates at a speed 10 times lower than the specified one. This lever can only be switched when the machine is stopped.
Feed rate knobs- these handles set the speed of movement of the cutting tool when processing parts, as well as the movement of the cutting tool per one revolution of the spindle when cutting threads. The handles can only be moved when the machine is stopped.
Spindle- steel thick-walled pipe. The spindle is used to transmit rotation from the electric drive, through a system of gears, to the workpiece. The spindle entry on the surface is threaded for mounting fixture chucks, and the entry is cone shaped for mounting centers or other fixtures.
It should be noted that for different models of machines, the number and position of the handles for setting the speed of rotation and movement may differ from those shown in the figure. For a specific model of lathe, you should carefully read the designations on the nameplates or read the operating instructions for the machine.
tailstock
tailstock- a fixture for fixing a workpiece (when processing in centers), or for fixing tools, such as a tap, die when threading; drill or drill chuck when drilling holes.
caliper
The support of the lathe is designed to secure and move the cutting tool.
Rotary tool post- a device for fixing and changing the cutting tool.
Handle for fixing the tool holder- designed to change the cutting tool. To change the tool, the handle is turned counterclockwise (away from you), while the tightening head loosens the fixation of the tool holder and it turns. To fix the tool holder, turn the tool holder fastening knob clockwise (towards you) until it stops.
Top slide- a mechanism for moving the tool holder in a given direction. The upper slide can be rotated (in a parallel plane) relative to the machine axis by a given angle. This will be discussed in detail in the topic "Machining conical surfaces".
Top slide handle- Rotation of this handle moves the upper slide in a horizontal plane.
cross slide- designed to move the cutting tool in a horizontal plane strictly perpendicular to the axis of the machine.
Cross slide handle- clockwise rotation of this handle moves the cross slide forward (towards the machine axis), and counterclockwise backwards (away from the machine axis).
Longitudinal slide- a device for moving the cutting tool strictly parallel to the axis of the machine.
Longitudinal slide wheel- rotation of this wheel counterclockwise leads to horizontal movement of the cutting tool from right to left, and clockwise - from left to right.
Screw feed switch- used only when cutting threads with a cutter. In all other modes of processing parts, this switch is disabled.
Feed switch- multi-position lever to enable automatic movement of the cutting tool in a given direction.
In position 0 - (neutral), the caliper stands still; in positions 1 or 2, the cross slide moves (forward or backward, respectively); in position 3 or 4, the longitudinal slide moves (to the left or right, respectively).
Feed switches may have another design, for example, have two levers. One includes longitudinal, and the other transverse feed.
Drive shafts and mechanisms
To automatically move the elements of the caliper, as well as to quickly turn on and off the rotation of the spindle, the lathe has several drive shafts and corresponding mechanisms.
The mechanisms for switching on and off various drives are located in the support under the apron.
Spindle engagement shaft- has two handles of inclusion of a spindle. One handle is located to the left of the machine operator, and the second to the right. Both handles are rigidly fixed on the shaft. Moving any of these knobs up turns on the machine and the spindle starts to rotate counterclockwise (working, forward rotation). In the middle position of the handles - the machine is turned off. When you move the knobs down, the spindle starts to rotate clockwise (reverse rotation).
Rack- an integral part of the mechanism for manually moving the caliper in the longitudinal direction. During the rotation of the wheel for moving the longitudinal slide, the gear wheel connected to the axis of rotation of the wheel and the gear rack engages, while the caliper moves.
Feed shaft- This shaft is designed to automatically move the cutting tool. The shaft along its entire working length has a longitudinal groove that serves to engage with the movement mechanism. When the machine is running, this shaft is constantly rotating. The feed switching knob activates the mechanism of the selected movement.
Threaded Shaft (Screw)- designed to drive the caliper in the longitudinal direction when cutting threads with a cutter. This shaft rotates only in threading mode.
limbs
A limb is a ring (or a flat washer) with risks applied on its surface, located at equal distances from each other. At a certain interval, for example, every 10 marks, numbers are applied indicating a certain amount of graduation of the limbus. The limb can be graduated in millimeters, degrees, or other metric units.
The figure shows the dial located on the mechanism for moving the cross slide. The rotation of the limb occurs in conjunction with the rotation of the handle for moving the tool. Every tenth risk on the limb is numbered 0, 1, 2 ..19. In total, the limb has 200 risks. In this case, when turning the handle, for example, by 10 divisions (from 0 to 1), the working tool will move 1 millimeter.
Different machines have different graduations of dials, so you should consult the operating instructions for a particular machine. If it is not possible to find out this information, then you can determine the amount of displacement yourself. To do this, turn the part and measure the resulting size, then turn the part again by turning the handle ten divisions and again measure the size obtained after turning. The difference between the previous and last measurement will be exactly the amount of movement of the tool when rotated by 10 divisions.
The dial ring can be rotated on the axis of the mechanism by holding the movement handle. This may be necessary to set a reference point during processing, usually set to 0.
Main types and characteristics of lathes
Lathes have certain characteristics that should be taken into account when manufacturing certain parts on them: Details about the types of modern machines can be found on the website "Machines for your production".
For the accuracy of the installation and processing of parts in lathes, special units are responsible - lathe headstocks.
Spindle (front) headstock- a lathe device designed to communicate a workpiece with rotational motion. The workpiece is fixed in a collet, chuck, faceplate mounted on the spindle or fixed in centers between the headstock and tailstock. The rotational speed of the workpiece and its direction can be adjusted.
Rear (thrust) grandma- a lathe unit for fixing (compressing) workpieces with the help of a persistent or rotating center, as well as for installing cutting tools: drills, countersinks, reamers.
Lathe headstock device (spindle assembly)
The headstock consists of a spindle installed in the body, a unit for changing the direction of rotation and adjusting the speed, a start and stop mechanism.
The body of the spindle device can have a different shape; as a rule, it is cast from cast iron. In modern machines, the rigid body of the headstock has precise holes for mounting the front and rear spindle bearings.
The transmission of rotational motion from the engine to the spindle is carried out by means of V-belts and gears gear train. In CNC turning group machines, the encoder perceives the rotation of the spindle and converts it into an electrical impulse sent to the CNC module. In turn, the controller controls the operation of the drive servomotor for gradual (not discrete) regulation of the spindle speed.
The spindle assembly, as a rule, has a circulation lubrication system.
Spindle - a hollow shaft made of carbon steel, into the hole of which long workpieces are passed. The spindle is installed in the headstock housing by means of front and rear bearing assemblies.
Spindle nose of lathes foreign production complies with ISO 702/1. On modern CNC machines, depending on customer requests, the geometry of the spindle nose can be changed. A clamping device is installed on the end: lathe chuck, collet, faceplate, thrust center.
The seating surfaces of the spindle nose have a finish of at least 6 quality (in precision machines it is much higher), during manufacture the surface is hardened and ground (Ra not lower than 1.25), and its outer diameter is strictly concentric with the axis of rotation. Otherwise, the radial and axial runout of the chuck or other clamping device mounted on the spindle will exceed the allowable values. This will affect the accuracy of the workpiece processing.
In this regard, when changing the clamping equipment, the seating surfaces of the spindle must be protected from various kinds of damage, and the runout of the newly installed chuck or collet must also be checked.
Accuracy check
The geometric accuracy of processing, for example, on CNC lathes, is checked in this way: a workpiece with a diameter of 200 mm and a length of 500 mm is clamped into a lathe chuck and turned along cylindrical surface without tailstock clamping. Permissible deviation from cylindricity - 0.04 mm at a length of 300 mm from the end of the cartridge.
If the results are unsatisfactory, the headstock of the lathe is adjusted: the installation of optimal clearances in the angular contact and thrust bearings of the spindle, which perceive the radial and axial force during the operation of the equipment.
Lathe tailstock device
The thrust headstock consists of a plate (a base resting on the guide beds, a body with a sleeve in which the working quill is installed, a flywheel (quill movement wheels)) and handles for fixing the quill and tailstock. In front of the quill there is a conical hole that serves to install and fix fixtures and tools.
Consider the device 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 - guitar of interchangeable wheels, 3 - feed box, 4 - frame, 5 - apron, 6 - caliper, 7 - tailstock, 8 - cabinet with electrical equipment.To study the device of a lathe, consider the main elements according to the scheme:
Headstock 1- cast iron box, the main working body is the spindle and gearbox. It serves to fix the workpiece and transmit to it the main movement - rotation. The most critical part of the headstock is the spindle, which is a hollow steel shaft. At the front end of the spindle, an exact thread is cut into which a cam or driver chuck or faceplate can be screwed. At the same end of the spindle there is a tapered hole into which the front center can be inserted.
Guitar 2- is necessary to adjust the feed or pitch of the thread being cut by the machine by installing the appropriate replaceable gears. Mostly not used in modern machines.
Delivery box 3- This is a machine node that transmits rotation from the spindle to the lead screw or lead shaft. With the help of it, the speed of rotation of the lead screw and the lead shaft is changed, which achieves the movement of the caliper at the selected speed in the longitudinal and transverse directions.
Bed 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 running shaft into the longitudinal or transverse movement of the caliper.
Caliper 6- designed to move the tool holder with a cutter in the longitudinal, transverse and inclined directions to the axis of the machine. The cutter can be told to move along and across the frame both mechanically and manually.
The caliper consists of a carriage that moves along the guides of the bed, an apron, in which there is a mechanism for converting the rotational movement of the drive shaft and the lead screw into the rectilinear movement of the caliper, the mechanism of the cross slide, the mechanism of the incisive (upper) sled, the mechanism tool holder.
Tailstock 7- necessary for setting the end of long workpieces in the process of processing, as well as for fixing and feeding core tools (drills, countersinks, reamers).
Cabinet with electrical equipment 8 - Starting the electric motor, starting and stopping the machine, controlling the operation of the gearbox and feed box, controlling the apron mechanism, etc., is carried out by the appropriate controls (handles, buttons, handwheels). Also, in addition to the machine, a lathe can be used: chucks, faceplates, collets, centers, clamps, lunettes, mandrels (for fixing workpieces).
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At the same time, special cutters of various shapes are used to perform these works. They are the main cutting tool in such a machine. To make a hole, drills, countersinks and reamers are also used. If there special devices, then the lathe is quite suitable for grinding, milling, cutting teeth.
Depending on where the spindle is located, which carries the fixture for holding the workpiece, it is customary to divide lathes into vertical and horizontal.
What is a lathe made of?
The basis of the lathe is always the bed. This is the name of a fairly massive support, on which all the nodes of the machine are fixed. The most important requirement that is placed on the frame is its strength. The mass of the bed must be such as to prevent the machine from tipping over. The vibration level should also be kept to a minimum.
The lathe consists of the following main components: the headstock (which is also called the spindle), the tailstock, the bed, the feed box, and the caliper with an apron.
It should be remembered that the headstock is the most difficult part. It includes a gearbox with a spindle on it and a block electronic control. The caliper and tailstock move along the bed guides. An electric motor is located under the casing of the headstock.
The tailstock moves along the frame along the axis of rotation. Its purpose is to press the workpiece against the leading center, which is located on the spindle. An integral part of the tailstock is the quill. A center is attached to it, rotating or not rotating. He rests his edge on the workpiece. The workpiece is fixed in the spindle chuck or in the centers of the headstock or tailstock.
It is possible to adjust the rotation speed of the workpiece in accordance with the cutting mode. The support for the cutter is the handpiece. The support provides a rigid fastening of the cutter. It also allows the cutter to accurately move in all three axes.
There are the following types of lathes: screw-cutting lathe, lathe-carousel, frontal lathe, turret lathe, longitudinal turning machine, multi-spindle lathe machine, turning-milling machining center. A special type of lathes are lathes with numerical software.
