Specialists from machine-building enterprises who attend foreign exhibitions of metalworking equipment are witnesses to the success of such a technical solution as the combination of several technological operations and even processes on one machine, and in various combinations. It seems that there are no operations left in production, even the most difficult to combine, that would not be combined in an attempt to increase the accuracy and productivity of processing by reducing the number of reinstallations.

This idea, which originated a long time ago and was actually implemented in 1992 by Emag, which presented an inverted vertical lathe at the METAV92 exhibition, became a real material force just a few years later. Proof of this is over 5,000 machines of this configuration, sold to various factories, mainly automobile and tractor ones. On its basis, it became possible to combine turning, predominantly hard turning, for difficult-to-cut steels and alloys with a hardness of over 45HRC, with abrasive processing, also for the first time in the world, carried out in 1998 by the same company Emag, but already together with the company Reinecker, which was part of it, on a machine Maud. VSC250DS (Fig. 1).

When the benefits are obvious

Since then, the advantages of this arrangement have become apparent to many other German, Swiss and Italian companies producing both lathes and grinding machines. For turning centers, they consist in the possibility of using dry and hard turning, and in some cases, grinding parts without large diameter(up to 400 mm, only the G 250 machine from Index has a processing diameter of 590 mm), but quite long. There are many such parts such as gears and various disks found in the automotive industry.
In addition, processing productivity is increased, since the allowance for grinding after turning can be increased to several hundredths of a millimeter (in reality it usually reaches several tenths), and its accuracy, which is ultimately determined by grinding. To date, such combined machines are produced by several companies, mainly German, whose main field of activity is, as shown in Table 1, the production of not only turning centers (Emag, Index, Weisser), but also grinding machines (Junker, Buderus Schleifmaschinen, Schaudt Mikrosa BWF). Their cost varies widely and is determined primarily by the layout, design and complete set.

The EMO 2003 exhibition showed that interest in combined machines for hard turning and grinding is growing. Along with the companies Emag, Index, Weisser, Buderus, Schaudt Mikrosa BWF, which previously exhibited machines for combined turning and grinding, similar products were demonstrated by other manufacturers of machine tool equipment. For example, the Tacchella company (Italy) showed a prototype of the Concept cylindrical grinding machine, equipped with an 8-position turret with fixed tools (Fig. 2), and the Meccanodora company (Italy) showed a serial Futura machine for hard turning and milling, as well as external and internal grinding transmission parts. The Stratos M, first shown by Schaudt Mikrosa BWF at the EMO 2001 exhibition, was additionally equipped with an 8-position turret.

Combined processing

For parts passing through a turning-grinding center, for example, electric motor shafts, in most cases it is not necessary to grind all surfaces - mainly only the supporting ones or the most worn ones. For the rest, turning is quite enough. In such cases, where tight dimensional tolerances and high quality surfaces are needed only in certain areas of the part; the use of lathes with grinding capabilities is fully justified, especially since processing on them occurs in one setup. If the workpiece has many steps, most of which are subject to grinding, then it must be processed on a grinding machine with the ability to turn.

Thus, processing is carried out on a grinding machine if:

the workpieces are made of materials that are difficult to machine, not amenable to or difficult to turn;
the required tolerances exceed those achievable during turning;
the required surface quality is so high that it cannot be achieved during turning, including hard turning.

A lathe is used for processing when:

the complex geometry of the workpiece makes processing with a blade tool with a point cutting edge (for example, a cutter) more effective than with a relatively wide grinding wheel;
the volume of material removed is relatively large and exceeds the capabilities of removal by grinding;
processing of discontinuous surfaces is necessary.

Many parts have both requirements, so combining grinding with hard turning on one machine increases its flexibility and allows each operation to be optimized.

Design features of the machines

An analysis of the machines presented in Table 1 shows that the vast majority of them have a vertical layout, which for relatively short parts (with a diameter greater than the length), usually subjected to turning and grinding, turned out to be more effective than a horizontal one. Processing of fairly long shafts (from 600 mm for the Emag HSC250DS model to 1400 mm for the Index G250 model) remains an exception and is carried out only on horizontal machines. In addition, most machines, in order to increase their efficiency, are equipped with conveyors for feeding workpieces and removing finished parts from the working area. One of the means of increasing the rigidity of machines subjected to increased loads during combined processing is the use (for machines from Emag, Schaudt BWF Mikrosa and some others) of polymer concrete frames that have good damping properties, as well as (for machines from Buderus) frames made of natural granite.

Almost all machines are equipped as standard with more than one grinding spindle in order to be able to carry out both external and internal machining. In this case, the straightening mechanism is built directly into the machine. Note that almost all companies offer linear motors as options, not only along the longitudinal axis, along which maximum movement occurs, but also along the transverse one. This means that the productivity of such machines can be further improved.

Of course, lathe manufacturers such as Emag and Index and grinding machine manufacturers such as Junker, with the common goal of providing high flexibility, productivity and machining efficiency when choosing an approach to the design of their equipment that combines hard turning with grinding or vice versa - are guided by various considerations. As a rule, this design is made in such a way that the machine, in addition to turning and grinding, has the ability to perform other operations, if necessary.
So, the machine mod. Index's V300 has an inverted vertical spindle design (inspired by Emag) and is designed to handle a wide range of workpieces of any type (castings, forgings, etc.). Their loading and unloading is done automatically. Thanks to the modular design, the machine, which is equipped with a large number of tool heads and blocks that can be combined in any order (Fig. 3), designed to perform various operations of turning, drilling and grinding, can work in both small- and medium-scale production. During the processing process, the spindle moves the workpiece, bringing it to various tool blocks installed on the bed, which carry out the specified operations of turning, drilling, external and internal grinding. To perform combined hard turning and grinding, a turret with stationary and rotating tools is mounted on the frame. The external grinding unit uses grinding wheels with a diameter of 400 mm and a width of 40 mm made of traditional and super-hard materials, such as CBN, rotating at a frequency of up to 6000 rpm from a 7.5 kW drive. They are edited automatically. The unit has a built-in electromagnetic grinding wheel balancing system. Internal grinding is carried out with wheels made of the same materials, but mounted on mandrels with a HSK32 cone to obtain maximum precision and rigidity of the grinding spindle. The high-frequency spindle for their rotation has a power of 2 to 15 kW and is designed for a rotation speed in the range of 45,000-100,000 rpm. Additional operations on this machine can be performed using a diode laser built into manufacturing process to perform hardening of the outer surfaces, as well as the ends and individual sections on the inner surfaces, on a workpiece clamped in the spindle chuck. An additional operation is also rolling, performed on a mod machine. CNC 435 from Buderus.
Multifunctional machines- the type of equipment for blade processing that is currently most successfully developing, and in many aspects, is not something particularly new for abrasive. Using grinding wheels, built-in, for example, into the magazines of some milling machining centers, semi-finishing and finishing machining of complex surfaces of parts made of difficult-to-machine materials, such as turbine blades, has long been performed. Basic technological advantages such centers - a decrease in the number necessary equipment and, accordingly, the required production areas and the number of operators, the possibility of transferring finished parts directly to assembly - are also preserved for multifunctional machines based on grinding machines. However, this equipment for combined grinding and turning has a number of differences and advantages. It should be noted, in particular, the significant predominance of grinding operations over turning, milling and drilling, the mandatory cooling of the working area, and the presence in some cases of a wheel changing mechanism during grinding. It is also necessary to consider as an advantage that when performing lathe, milling, thread-cutting and other blade operations on grinding machines, greater accuracy is achieved than when performing them on lathes and/or milling machines, because grinding machines that are converted into multifunctional ones initially have more higher accuracy than, for example, in turning machines, which are given the ability to grind. Such machines are produced by the Swiss company Magerle and the German company Junker.
The modular MMS machine (Fig. 4), first shown by Magerle at the EMO2003 exhibition, has a symmetrical portal design, which, together with ball screws along the coordinate axes, ensures its static and dynamic rigidity and thermal stability. Movements along three coordinate axes (500x250x200 mm) through these gears are performed by the table, which allows you to install horizontal, vertical or inclined grinding heads on the machine and manually or automatically load it from four sides. At the exhibition, in particular, a version of the machine was shown with a vertical motor spindle with a power of 30 kW and a built-in tool changer (five grinding wheels with a diameter of 300 mm, a width of 60 mm and a weight of no more than 20 kg, or 20 wheels with a diameter of no more than 130 mm), produced in 3 seconds. The rotation speed of the circles is recommended within 1000-8000 min -1. The HSK-A-100 spindle cone can also accommodate cutters, drills and other blade tools, which, when combined with a two-axis dividing head and a satellite changer, allows the processing of small pump blades, turbine blades and other complex parts. This is facilitated by the ability to supply coolant through the center of the spindle at a pressure of 80 bar.
A prototype of the Concept multifunctional machine, which was also shown for the first time at this exhibition by the Italian company Tacchella Macchine, is a combination of a conventional cylindrical grinding machine with an eight-position turret in which stationary tools are installed. Two circles of large diameter made of CBN are rotated on the machine relative to each other by 180 degrees and can be rotated in turn in work area. The machine bed is made in the form of a rigid ribbed cast iron casting. Movements along the X and Z axes can be performed using linear motors or ball screws. Hydrostatic guides are used to move the working parts. The disadvantages of this machine include the fact that it does not have separate working areas for turning and grinding. In the future, apparently, rotating tools will also be installed in the turret, which will expand the technological capabilities of the machine, and the number of turrets can be increased to two.
On the Hardpoint 300 series machine of modular design from Junker with an inclined bed, hardened and non-hardened parts such as rotation bodies with a diameter of 80 mm and the same length (Fig. 5) in addition to grinding and honing with wheels and CBN heads can be used for turning, drilling and reaming in one setup , as well as cutting threads and removing burrs. The machine is implemented in four versions with a number of spindles from two to four, in which up to four parts can be processed simultaneously with or without transmission from one spindle to another. The machine is controlled along six coordinate axes from the Sinumerik 840D CNC device. The machine can be loaded manually or automatically.

High performance machine mod. CNC235 from Buderus Scheiftechnik (Fig. 6) is achieved by installing two spindles on it, allowing external and internal grinding (with special heads) and hard turning (with separate cutters or a turret) of workpieces with a diameter and length of up to 150 mm, as well as a belt conveyor.

Multifunctional machines designed for hard turning and grinding of heat-treated workpieces are in fairly high demand among consumers abroad and are gradually beginning to penetrate into Russia. There is information about the installation of one such machine (by Buderus) at the Volgoburmash plant. Two machines mod. Stratos M was delivered to VAZ in 2004. At the same time, 60 such machines are already operating in Europe, the USA and Southeast Asia. The reason for such a sharp difference is the insufficient level of development of most sectors of our industry and the insufficient efficiency of such complex and expensive equipment in our economic conditions, and, consequently, the minimal demand for it. Therefore, in the near future one should not expect the appearance of large quantity machines for dry turning and grinding, except at individual enterprises in the automotive industry and several enterprises producing equipment for the oil and gas industry.

Vladimir Potapov
Magazine "Equipment: market, supply, prices", No. 07, July 2004.

In order to improve the surface quality or increase the accuracy of parts, the following can be performed on lathes: finishing operations: polishing with abrasive sandpaper, lapping (finishing) surfaces, rolling outer surfaces and rolling out holes with rollers or balls, as well as knurling.

Polishing with abrasive sandpaper is used to obtain a clean surface for parts of low precision. Abrasive sandpapers with large grains (No. 6, 5 and 4) are used for cleaning rough, untreated surfaces. Medium grain sandpapers (No. 3 and 2) are used for polishing surfaces with V4 treatment. Polishing with fine-grained sandpapers (nos. 1 and 0) provides a surface with a cleanliness of V 5, V 6. And finally, polishing with very fine-grained sandpapers (sandpapers no. 00 and no. 000) produces surfaces with a cleanliness of V 7, V 8 and even V 9.

When polishing, the machine is turned on at medium or maximum speed (depending on the diameter of the product), the sandpaper is pressed against the surface being processed with three fingers and slowly moves back and forth along the product. A strip of sandpaper can also be held taut by the ends with both hands and, pressing it against the product, polished. When processing products of small diameter, presses are used - a device consisting of two wooden blocks hingedly connected to each other. The bars have depressions corresponding to the diameter of the workpiece. Abrasive sandpaper is inserted into the recesses of the press or abrasive powder mixed with oil is applied. When polishing, the clamp is compressed with the left hand and moved along the product.

It is advisable to carry out polishing using a cutting fluid. Final polishing is done with sandpaper rubbed with chalk.

Lapping (finishing) of surfaces serves to finalize surfaces after fine turning, boring, grinding or reaming. Using lapping, you can achieve class 1 accuracy and surface cleanliness according to Vl2-Vl3. Lapping of external cylindrical surfaces is carried out using laps having the shape of a split sleeve. The internal diameter of the lap should be greater than the diameter of the product by 0.15 mm during roughing and by 0.05 mm during finishing. The wall thickness of the lap should be from 1/6 to 1/8 of its diameter. The lap is made of cast iron for processing hardened steel and of bronze, brass or copper for other metals and alloys.

The lapping sleeve is coated from the inside with fine abrasive powder mixed with oil, or coated with GOI finishing paste. The lap is inserted into a metal clamp and put on the part. The bolt ensures slight uniform pressure between the lap and the part. Lapping is performed at speed rotational movement 10-20 m/min with a slow reciprocating movement of the lap along the part. The lapping allowance is set to 0.015 mm for parts with a diameter of 10-20 mm and 0.025 mm for diameters of 20-75 mm.

Hole lapping diagram. The lap sleeve is put on a conical mandrel fixed in the chuck. The taper of the mandrel is assumed to be 1/30. The outer surface of the lap is covered with abrasive powder mixed with oil or GOI paste. The part is put on the lap with light force. To ensure the correct shape of the hole, the length of the lap must be greater than the length of the hole.

Rolling of corrugations. Corrugations applied to parts of devices, devices, tools can be straight or cross. They are performed by rolling with special rollers fixed in a holder. For straight corrugations, one roller of the appropriate pitch is used; for cross corrugations, a holder with two rollers located exactly one above the other is used. On the cylindrical surface of the rollers, teeth of a certain pitch are applied, the size of which depends on the diameter of the product. With direct corrugation, the teeth are located parallel to the roller axis, with cross corrugation, they are inclined in the opposite direction.

The holder with rollers is installed in the tool holder along the line of centers, perpendicular to the axis of the product. Using a transverse feed, the roller is pressed with force into the surface of the rotating product. After several revolutions, the roller teeth are checked to ensure that they are in the grooves they have made, and then the mechanical longitudinal feed is turned on. Knurling is performed in 4-8 passes on parts made of steel and in 6-10 passes on parts made of non-ferrous metals. The peripheral speed of the part is 10-25 m/min for steel and 50-100 m/min for non-ferrous metals. Rolling is carried out with lubrication with machine or spindle oil. The roller groove is periodically cleaned of adhered metal particles.

Finishing operations - polishing, finishing, rolling, rolling, smoothing and rolling are performed to reduce roughness, increase dimensional accuracy and wear resistance of a previously treated surface or to apply corrugations of a certain pattern to it.

Polishing

Polishing is performed to reduce the roughness and increase the gloss of the surfaces of the part. On lathes it is carried out using sandpaper on paper or canvas. Steel and non-ferrous metals are treated with corundum skins 15A-25A, cast iron and other brittle materials - with silicon carbide skins 54C-64C.

During operation, a strip of sandpaper is held with both hands, pressed against a rotating polished surface and moved back and forth along it. You cannot hold the skin with your hand, as it can wrap around the part and pinch your fingers. It is necessary to stand at the machine with the body turned to the right at approximately an angle of 45° to the center axis. Polishing is usually performed sequentially with several sandpapers with a gradual decrease in their grain size.

It is convenient to polish cylindrical surfaces with a “press”, consisting of two hinged wooden blocks. Sanding paper is placed in the radial recesses of the bars, which is pressed with a press to the surface to be treated. Holding the handles of the press with your left hand and supporting the hinge with your right, carry out a reciprocating longitudinal feed.

Polishing can also be carried out by securing the abrasive paper in the caliper tool holder using wooden block and metal strip .

The internal surfaces are polished with sandpaper secured and wound on a wooden mandrel.

The part being polished becomes very hot and elongates. Therefore, when it is pressed by the center, you need to periodically check how tightly it is clamped and, if necessary, loosen it a little.

To obtain a better surface, it is necessary to increase the rotation speed of the part as much as possible. In addition, during final polishing, it is recommended to rub the skin with chalk.

Finishing

Finishing is carried out to increase the accuracy of the surface (up to 5-6th quality) and reduce its roughness. Using special tools - laps - together with abrasive materials, the smallest irregularities are removed from the surface of the part.

Abrasives and binding materials. Working surface The lapping is saturated with hard abrasive materials: electrocorundum powders - for finishing steels and silicon carbide - for cast iron and other brittle materials.

The grain size of the powders is selected depending on the required roughness. Preliminary finishing is performed with micropowders M40-M14, finishing finishing with M10-M5 (the micropowder number corresponds to the grain size in microns).

Of the finishing pastes, the most commonly used are GOI pastes, made on the basis of a soft abrasive material - chromium oxide mixed with chemically active and binders. According to finishing ability, such pastes are divided into coarse, medium and fine.

Kerosene or mineral oil are used as binders and lubricants during finishing.

Lapping bushings with longitudinal section, allowing them to be adjusted in diameter to compensate for wear.

Lappings for preliminary finishing are equipped with longitudinal or helical grooves, in which the remains of abrasive material are collected during operation. Final finishing is carried out using laps with a smooth surface.

The finishing of the outer surface is carried out using a lapping device, which is installed in the clamp and adjusted as necessary with a screw. .

To machine holes, the lap is mounted on a conical mandrel and adjusted by axial movement with nuts. The lap material is selected depending on its purpose and the abrasive material used.

When finishing with hard abrasive materials, the grains of which are pressed into the lap, the material of the latter must be softer than the material of the workpiece. In addition, the larger the grains of the powder used, the softer material should be selected for lapping. For rough finishing, laps made of mild steel, copper, brass are recommended, and for preliminary and finishing - from fine-grained gray cast iron of medium hardness.

To work with GOI pastes, the lap must have greater hardness than the part being finished. In this case good results allows the use of laps made of hardened steel or gray cast iron of increased hardness.

The peripheral speed of the part or lap is assumed to be 10-20 m/min during preliminary finishing, and 5-6 m/min during finishing in order to reduce heating of the part.

Rolling

Purpose and tools. Rolling is performed to create on the surfaces of some parts (handles, screw heads, etc.) a specially designed roughness, made in the form of corrugations of a certain pattern. For this purpose, knurling tools are used, consisting of a knurling roller and a holder.

To apply a straight pattern, single-roller knurling is used, mesh-double-roller knurling, respectively, with the right and left directions of the corrugations.

Knurling rollers are made of tool steels and hardened to high hardness. On their cylindrical surface, corrugations are made with a profile angle of 70° for steel parts and 90° for parts made of non-ferrous metals with a pitch of 0.3 to 1.6 mm.

The knurling is fixed with the smallest overhang in the tool holder of the caliper so that the generatrix of the roller is strictly parallel to the axis of the part. Check this against the surface being treated against the light. The axis of the single-roller knurling roller should be at the level of the center axis of the machine. For double-roller knurling, the accuracy of height adjustment is not significant, since in

In this case, the rollers self-align on the surface being processed due to the swivel connection between the holder and the holder .

Rolling techniques. When rolling, the metal is squeezed out, so the surface of the part is ground to a diameter that is approximately 0.5 knurling pitch less than the nominal one.

The rollers are brought close to the rotating part and, using manual feed, are pressed into the surface to be processed to a certain depth. Turning off the rotation of the part, check the accuracy of the resulting pattern. Then the spindle rotation and longitudinal feed are turned on and rolling is performed to the required length in several passes in both directions until the full height of the corrugations is obtained. At the end of each pass, without breaking contact with the workpiece, the knurling is applied transversely to

required depth. Knurling rollers should be periodically cleaned with a wire brush to remove metal particles stuck in the recesses.

The longitudinal feed is taken to be approximately equal to twice the corrugation pitch (1-2.5 mm/rev), the rotation speed of the part is within 15-20 m/min.

The surface to be treated is lubricated with oil.

To main

section five

Basic operations and work,
performed on a lathe

Chapter XI

Turning external cylindrical surfaces

Lathes can be used to process parts whose surfaces have the shape of bodies of revolution. Most parts used in mechanical engineering have cylindrical surfaces, such as rollers, bushings, etc.

1. Cutters for longitudinal turning

For longitudinal grinding, through cutters are used. Passing cutters are divided into rough And finishing.

Rough cutters (Fig. 99) are intended for rough grinding - stripping, carried out in order to quickly remove excess metal; they are often called peeling. Such cutters are usually made with a welded or soldered, or mechanically attached plate and are equipped with a long cutting edge. The tip of the cutter is rounded along a radius of r = 1-2 mm. In Fig. 99, and the cutter of the roughing straight line is shown, and in Fig. 99, b - bent. The bent shape of the cutter is very convenient for turning the surfaces of parts located near the chuck jaws and for trimming the ends. After turning with a rough cutter, the surface of the part has large marks; As a result, the quality of the processed surface is low.

Finishing cutters are used for final turning of parts, i.e., to obtain accurate dimensions and a clean, smooth surface for processing. There are different types of finishing cutters.

In Fig. 100, and shows the finishing cutter, which differs from the rough cutter mainly in its large radius of curvature, equal to 2-5 mm. This type of cutter is used for finishing work that is performed with a small depth of cut and low feed. In Fig. 100, b shows a finishing cutter with a wide cutting edge parallel to the axis of the workpiece. This cutter allows you to remove finishing chips at high feed rates and gives a clean and smoothly machined surface. In Fig. 100, c shows V. Kolesov’s cutter, which allows you to obtain a clean and smoothly machined surface when working with high feed (1.5-3 mm/rev) with a cutting depth of 1-2 mm (see Fig. 62).

2. Installation and fastening of the cutter

Before turning, you need to correctly install the cutter in the tool holder, making sure that the part of the cutter protruding from it is as short as possible - no more than 1.5 times the height of its shaft.

With a larger overhang, the cutter will tremble during operation, as a result the processed surface will be unsmooth, wavy, with traces of crushing.

In Fig. 101 shows the correct and incorrect installation of the cutter in the tool holder.

In most cases, it is recommended to set the tip of the cutter at the height of the machine centers. To do this, use pads (no more than two), placing them under the entire supporting surface of the cutter. Lining It is a flat steel ruler 150-200 mm long, having strictly parallel upper and lower surfaces. The turner must have a set of such shims different thicknesses to obtain the height required for installing the cutter. You should not use random plates for this purpose.

The shims must be placed under the cutter as shown in Fig. 102 on top.

To check the height position of the cutter tip, bring its tip to one of the pre-calibrated centers, as shown in Fig. 103. For the same purpose, you can use a mark placed on the tailstock quill, at the height of the center.

Fastening the cutter in the tool holder must be reliable and durable: the cutter must be secured with at least two bolts. The bolts securing the cutter must be tightened evenly and tightly.

3. Installation and fastening of parts in centers

A common way of processing parts on lathes is processing in centers(Fig. 104). With this method, center holes are pre-drilled at the ends of the workpiece - center detail. When installed on a machine, these holes accommodate the center points of the machine's headstock and tailstock. To transmit rotation from the headstock spindle to the workpiece, it is used driving chuck 1 (Fig. 104), screwed onto the machine spindle, and clamp 2, secured with screw 3 on the workpiece.

The free end of the clamp is captured by the groove (Fig. 104) or finger (Fig. 105) of the cartridge and causes the part to rotate. In the first case, the clamp is made bent (Fig. 104), in the second - straight (Fig. 105). The pin driver cartridge shown in Fig. 105, poses a danger to the worker; A driver chuck with a safety casing is safer (Fig. 106).

The essential accessories of a lathe are centers. Typically the center shown in Fig. 107, a.

It consists of a cone 1, on which the part is mounted, and a conical shank 2. The shank must fit exactly into the conical hole of the headstock spindle and the tailstock quill of the machine.

The head center rotates with the spindle and the workpiece, while the tailstock center is mostly stationary and rubs against the rotating workpiece. Friction heats up and wears out both the conical surface of the center and the surface of the center hole of the part. To reduce friction, the rear center must be lubricated.

When turning parts at high speeds, as well as when processing heavy parts, working on a fixed center of the tailstock is impossible due to the rapid wear of the center itself and the development of the center hole.

In these cases, use rotating centers. In Fig. 108 shows one design of a rotating center inserted into the tapered hole of the tailstock quill. Center 1 rotates in ball bearings 2 and 4. Axial pressure is perceived by thrust ball bearing 5. The tapered shank 3 of the center body corresponds to the conical hole of the quill.

To reduce the time required to secure parts, clamps with manual clamping are often used instead of clamps. grooved front centers(Fig. 109), which not only center the part, but also act as a leash. When pressed by the rear center, the corrugations cut into the workpiece and thereby transmit rotation to it. For hollow parts, external (Fig. 110, a) are used, and for rollers, internal (reverse) corrugated centers are used (Fig. 110, b).

This fastening method allows you to grind the part along its entire length in one installation. Turning the same parts with a conventional center and collar can be done in only two settings, which significantly increases the processing time.

Used for light and medium turning work self-clamping clamps. One of these clamps is shown in Fig. 111. In the body 1 of such a clamp, a cam 4 is installed on the axis, the end of which has a corrugated surface 2. After installing the clamp on the part, the corrugated surface of the cam is pressed against the part under the action of the spring 3. After installation in the centers and starting the machine, finger 5 of the driving chuck, pressing on cam 4, jams the part and causes it to rotate. Such self-clamping clamps significantly reduce auxiliary time.

4. Setting up the machine for processing in centers

To obtain a cylindrical surface when turning a workpiece at centers, it is necessary that the front and work centers be on the axis of rotation of the spindle, and the cutter moves parallel to this axis. To check the correct location of the centers, you need to move the rear center towards the front (Fig. 112). If the centers do not align, the position of the tailstock housing on the plate must be adjusted as indicated on page 127.

Misalignment can also be caused by dirt or chips getting into the tapered holes of the spindle or pin. To avoid this, it is necessary to thoroughly wipe the spindle and quill holes, as well as the conical part of the centers, before installing the centers. If the center of the headstock still "beats" as they say, then it is faulty and must be replaced with another one.

During turning, the part heats up and elongates, creating increased pressure on the centers. To protect the part from possible bending, and the rear center from jamming, it is recommended to release the rear center from time to time, and then tighten it again to its normal state. It is also necessary to periodically additionally lubricate the rear center hole of the part.

5. Installation and fastening of parts in cartridges

Short parts are usually installed and secured in chucks, which are divided into simple and self-centering.

Simple chucks are usually made with four jaws (Fig. 113). In such chucks, each cam 1, 2, 3 and 4 is moved by its own screw 5 independently of the others. This allows you to install and secure various parts of both cylindrical and non-cylindrical shapes in them. When installing a part in a four-jaw chuck, it must be carefully aligned so that it does not hit when rotating.

The alignment of the part during its installation can be done using a thickness gauge. The surface scriber is brought to the surface being tested, leaving a gap of 0.3-0.5 mm between them; turning the spindle, watch how this gap changes. Based on the observation results, some cams are pressed out and others are pressed in until the gap becomes uniform around the entire circumference of the part. After this, the part is finally fixed.

Self-centering chucks(Fig. 114 and 115) in most cases three-jaw ones are used, much less often two-jaw ones are used. These chucks are very convenient to use, since all the cams in them move simultaneously, due to which a part having a cylindrical surface (external or internal) is installed and clamped exactly along the axis of the spindle; In addition, the time required to install and secure the part is significantly reduced.

In it, the cams are moved using a key, which is inserted into the tetrahedral hole 1 of one of the three bevel gears 2 (Fig. 115, c). These wheels are coupled to a large conical wheel 3 (Fig. 115, b). On the reverse flat side of this wheel, a multi-turn spiral groove 4 is cut (Fig. 115, b). All three cams 5 enter into the individual turns of this groove with their lower projections. When one of the gears 2 is turned with a key, the rotation is transmitted to the wheel 3, which, rotating, through the spiral groove 4 moves all three cams simultaneously and evenly along the grooves of the cartridge body. As the spiral-groove disk rotates in one direction or the other, the cams move closer or further from the center, respectively clamping or releasing the part.

It is necessary to ensure that the part is firmly secured in the chuck jaws. If the cartridge is in good condition, then a strong clamping of the part is ensured by using a key with a short handle (Fig. 116). Other methods of clamping, such as clamping with a key and a long tube placed over the handle, should under no circumstances be permitted.

Chuck jaws. The cams used are hardened and raw. Usually hardened cams are used due to their low wear. But when clamping parts with cleanly machined surfaces with such jaws, traces remain on the parts in the form of dents from the jaws. To avoid this, it is also recommended to use raw (unhardened) cams.

Raw jaws are also convenient because they can be periodically bored with a cutter and eliminate the chuck runout that inevitably appears during long-term operation.

Installing and securing parts in the chuck with support from the rear center. This method is used when processing long and relatively thin parts (Fig. 116), which are not sufficiently secured only in the chuck, since the force from the cutter and the weight of the protruding part can bend the part and tear it out of the chuck.

Collet chucks. To quickly secure short parts of small diameter to the outer machined surface, use collet chucks. Such a cartridge is shown in Fig. 117. With a conical shank, 1 chuck is installed in the conical hole of the headstock spindle. A split spring sleeve 2 with a cone, called a collet, is installed in the recess of the cartridge. The workpiece is inserted into hole 4 of the collet. Then screw nut 3 onto the cartridge body using a wrench. When screwing the nut, the spring collet compresses and secures the part.

Pneumatic chucks. In Fig. 118 shows a diagram of a pneumatic chuck, which provides quick and reliable fastening of parts.

At the left end of the spindle there is an air cylinder, inside of which there is a piston. Compressed air through the tubes it enters the central channels 1 and 2, from where it is directed to the right or left cavity of the cylinder. If air enters through channel 1 into the left cavity of the cylinder, then the piston displaces air from the right cavity of the cylinder through channel 2 and vice versa. The piston is connected to a rod 3 connected to a rod 4 and a slider 5, which acts on the long arms 6 of the crank arms, the short arms 7 of which move the clamping jaws 8 of the cartridge.

The stroke length of the cams is 3-5 mm. Air pressure is usually 4-5 am. To activate the pneumatic cylinder, a distribution valve 9 is installed on the gearbox housing, turned by handle 10.

6. Screwing and screwing of jaw chucks

Before screwing the chuck onto the spindle, thoroughly wipe the threads at the end of the spindle and in the chuck hole with a rag and then lubricate them with oil. A light cartridge is brought with both hands directly to the end of the spindle and screwed in until it stops (Fig. 119). It is recommended to place a heavy cartridge on the board (Fig. 120), bringing its hole to the end of the spindle, screw the cartridge until it stops, as in the first case, manually. When screwing on the chuck, you need to ensure that the axes of the chuck and the spindle strictly coincide.

To prevent cases of self-unscrewing of chucks in high-speed cutting machines, additional fastening of the chuck to the spindle is used using various devices

(screwing on an additional nut, securing the cartridge with shaped crackers, etc.).

Screwing the cartridge is done as follows. Insert the key into the chuck and pull towards yourself with both hands (Fig. 121).

Other methods of make-up involving sharp impacts on the chuck or jaws are unacceptable: the chuck is damaged and the jaws in its body become loose.

It is better to screw and unscrew a heavy cartridge with the help of an auxiliary worker.

7. Techniques for turning smooth cylindrical surfaces

Turning of cylindrical surfaces is usually carried out in two steps: first, most of the allowance is roughed out (3-5 mm per diameter), and then the remaining part (1-2 mm per diameter).

To obtain the specified diameter of the part, it is necessary to set the cutter to the required cutting depth. To set the cutter to the cutting depth, you can use the test chip method or use the cross feed dial.

To set the cutter to the cutting depth (by size) using the test chip method, you must:
1. Inform the details of the rotational movement.
2. By rotating the longitudinal feed handwheel and the cross-feed screw handle, manually move the cutter to the right end of the part so that its tip touches the surface of the part.
3. Having established the moment of contact, manually move the cutter to the right of the part and by rotating the handle of the cross-feed screw, move the cutter to the desired cutting depth. After this, the part is turned with manual feed to a length of 3-5 mm, the machine is stopped and the diameter of the turned surface is measured with a caliper (Fig. 122). If the diameter turns out to be larger than required, the cutter is moved to the right and set to a slightly greater depth, the belt is machined again and the measurement is taken again. All this is repeated until the specified size is obtained. Then turn on the mechanical feed and grind the part along the entire specified length. When finished, turn off the mechanical feed, move the cutter back and stop the machine.

Finish grinding is performed in the same order.

Using the cross feed screw dial. To speed up the installation of the cutter to the cutting depth, most lathes have a special device. It is located at the handle of the cross-feed screw and is a bushing or ring with divisions on its circumference (Fig. 123). This sleeve with divisions is called a limb. The divisions are counted according to the mark on the fixed screw hub (in Fig. 123 this mark coincides with the 30th stroke of the dial).

The number of divisions on the dial and the pitch of the screw can be different, therefore, the amount of transverse movement of the cutter when turning the dial by one division will also be different. Let's assume that the dial is divided into 100 equal parts and the cross feed screw has a thread with a pitch of 5 mm. With one full revolution of the screw handle, i.e., per 100 dial divisions, the cutter will move in the transverse direction by 5 mm. If you turn the handle by one division, then the movement of the cutter will be 5:100 = 0.05 mm.

It should be borne in mind that when moving the cutter in the transverse direction, the radius of the part after the passage of the cutter will decrease by the same amount, and the diameter of the part will decrease by doubled. Thus, in order to reduce the diameter of a part, for example from 50.2 to 48.4 mm, i.e. by 50.2 - 48.4 = 1.8 mm, it is necessary to move the cutter forward by half the amount, i.e. by 0.9 mm.

When setting the cutter to the cutting depth using the cross-feed screw dial, it is necessary, however, to take into account the gap between the screw and the nut, which forms the so-called “backlash”. If you lose sight of this, the diameter of the processed part will differ from the specified one.

Therefore, when setting the cutter to the cutting depth using a dial, the following rule must be observed. Always approach the required setting along the dial by slowly turning the screw handle to the right (Fig. 124, a; the required setting is the 30th division of the dial).

If you turn the handle of the cross-feed screw by an amount greater than required (Fig. 124, b), then to correct the error, in no case should you push the handle back by the amount of the error, but you need to make almost a full turn in reverse side, and then rotate the handle again to the right until the required division along the dial (Fig. 124, c). The same is done when it is necessary to move the incisor back; By rotating the handle to the left, the cutter is retracted more than necessary, and then by right rotation it is brought to the required division of the limb.

The movement of the cutter, corresponding to one division of the dial, by different machines various. Therefore, when starting work, it is necessary to determine the amount of movement that corresponds to one division of the dial on a given machine.

Using dials, our high-speed turners achieve the specified size without testing chips.

8. Processing parts in steady rests

Long and thin parts, the length of which is 10-12 times greater than their diameter, bend during turning both from their own weight and from the cutting force. As a result, the part receives irregular shape- in the middle it turns out to be thicker, and at the ends - thinner. This can be avoided by using a special support device called lunette. When using steady rests, you can grind parts with high precision and remove larger-section chips without fear of part deflection. The lunettes are motionless and movable.

Fixed rest(Fig. 125) has a cast iron body 1, to which a hinged cover 6 is attached using a hinged bolt 7, which makes installation of the part easier. The body of the steady rest is processed at the bottom according to the shape of the frame guides, on which it is secured by means of a strip 9 and a bolt 8. Two cams 4 are moved in the holes of the body using adjusting bolts 3, and one cam 5 is moved on the roof. Screws 2 are used to secure the cams in the required position This device allows the installation of shafts of various diameters into the steady rest.

Before installing the unturned workpiece into a stationary rest, you need to machine a groove in the middle for the cams, a width slightly larger than the width of the cam (Fig. 126). If the workpiece has a large length and a small diameter, then its deflection is inevitable. To avoid this, machine an additional groove closer to the end of the workpiece and, having installed a steady rest in it, machine the main groove in the middle.

Fixed steady rests are also used for cutting ends and trimming the ends of long parts. In Fig. 127 shows the use of a stationary rest when cutting the end: the part is fixed at one end in a three-jaw chuck, and the other is installed in the rest.

In the same way, you can machine a precise hole from the end of a long part, for example, bore a conical hole in the spindle of a lathe or drill such a part along its entire length.

Movable steady rest(Fig. 128) are used for finishing turning of long parts. The steady rest is secured to the support carriage so that it moves along with it along the part being turned, following the cutter. Thus, it supports the part directly at the point where the force is applied and protects the part from deflection.

The movable steady rest has only two cams. They are pulled out and secured in the same way as the cams of a fixed rest.

Steady rests with conventional cams are not suitable for high-speed machining due to rapid wear of the cams. In such cases, use Steady rests with roller or ball bearings(Fig. 129) instead of conventional cams, which makes the work of the rollers easier and reduces the heating of the workpiece.

9. Techniques for turning cylindrical surfaces with ledges

When processing on lathes a batch of step-shaped parts (stepped rollers) with the same length for all parts of individual steps, innovators use a longitudinal stop that limits the movement of the cutter and a longitudinal feed dial in order to reduce the time for measuring length.

Using the rip fence. In Fig. 130 shows a longitudinal stop. It is bolted to the front frame guide, as shown in Fig. 131; The place where the stop is secured depends on the length of the part to be turned.

If there is a longitudinal stop on the machine, it is possible to process cylindrical surfaces with ledges without preliminary marking, while, for example, stepped rollers are turned in one installation much faster than without a stop. This is achieved by placing a length limiter (measuring tile) between the stop and the support, corresponding to the length of the roller step.

An example of turning a stepped roller using stop 1 and measuring tiles 2 and 3 is shown in Fig. 131. Turning of step a 1 is carried out until the caliper rests against measuring tile 3. Having removed this tile, you can grind the next step of the roller, length a 2, until the caliper rests against tile 2. Finally, having removed tile 2, step a 3 is turned . As soon as the caliper reaches the stop, it is necessary to turn off the mechanical feed. The length of the measuring tile 2 is equal to the length of the ledge a 3, and the length of the tile 3 is equal to the length of the ledge a 2.

Hard stops can only be used on machines that have automatic feed shutdown when overloaded (for example, 1A62 and other new machine systems). If the machine does not have such a device, then turning against the stop can only be done if the mechanical feed is turned off in advance and the support is brought to the stop manually, otherwise machine breakdown is inevitable.

Using the longitudinal feed dial Using the longitudinal feed dial. To reduce the time spent on measuring the lengths of workpieces, modern lathes are equipped with longitudinal feed dial. This dial represents a rotating disk of large diameter (Fig. 132), located on the front wall of the apron and behind the longitudinal feed handwheel. Equal divisions are marked on the circumference of the disk. When the handwheel rotates, the dial, connected by a gear transmission to the longitudinal feed wheel, also rotates. Thus, a certain longitudinal movement of the support with the cutter corresponds to a rotation of the dial by certain number divisions relative to fixed marks.

When processing stepped parts, the use of a longitudinal feed dial is very rational. In this case, the turner, before processing the first part from the batch, first marks the length of the steps with a cutter using a caliper, and then begins to grind them. Having turned the first stage, he sets the longitudinal limb to the zero position relative to the stationary mark. While grinding the next steps, he remembers (or writes down) the corresponding dial readings regarding the same mark. When turning subsequent parts, the turner uses the readings established when turning the first part.

Using the Cross Stop. To reduce the time spent measuring diameters when machining stepped parts, a cross stop can be used on a number of lathes.

One of these stops is shown in Fig. 133. The stop consists of two parts. The fixed part 1 is installed on the carriage and secured with bolts 2; the thrust pin 6 is motionless. The movable stop 3 is installed and secured with bolts 4 on the lower part of the caliper. Screw 5 is set exactly to the required part size. The end of screw 5, resting against pin 6, determines the required size of the part. By placing 5-dimensional tiles between pin 6 and screw, you can grind parts with steps of different diameters.

10. Cutting modes when turning

Selecting cutting depth. The depth of cut when turning is selected depending on the processing allowance and the type of processing - roughing or finishing (see pages 101-102).

Feed rate selection. The feed is also selected depending on the type of processing. Usually the feed rate for rough turning is from 0.3 to 1.5 mm/rev, and for semi-finishing and finishing from 0.1 to 0.3 mm/rev when working with normal cutters and 1.5-3 mm/rev when working with cutters designs by V. Kolesov.

Cutting speed selection. The cutting speed is usually selected according to specially developed tables depending on the durability of the cutter, the quality of the material being processed, the material of the cutter, depth of cut, feed, type of cooling, etc. (see, for example, Table 6, p. 106).

11. Defects when turning cylindrical surfaces and measures to prevent it

When turning cylindrical surfaces, the following types of defects are possible:
1) part of the surface of the part remained unprocessed;
2) the dimensions of the turned surface are incorrect;
3) the turned surface turned out to be conical;
4) the turned surface turned out to be oval;
5) the cleanliness of the treated surface does not correspond to the instructions in the drawing;
6) combustion of the rear center;
7) mismatch of surfaces when processing the roller in the centers on both sides.

1. Defects of the first type are caused by insufficient dimensions of the workpiece (insufficient allowance for processing), poor straightening (curvature) of the workpiece, incorrect installation and inaccurate alignment of the part, inaccurate location of the center holes and displacement of the rear center.
2. Incorrect dimensions of the turned surface are possible due to inaccurate setting of the cutter to the cutting depth or incorrect measurement of the part when removing test chips. The causes of this type of defect can and should be eliminated by increasing the turner’s attention to the work being performed.
3. The taper of the turned surface is usually obtained as a result of a displacement of the rear center relative to the front. To eliminate the cause of this type of defect, it is necessary to correctly install the rear center. A common cause of rear center misalignment is dirt or small chips getting into the tapered hole of the quill. By cleaning the center and conical hole of the quill, this cause of defects can also be eliminated. If, even after cleaning, the points of the front and rear centers do not coincide, you need to move the tailstock body on its plate accordingly.
4. The ovality of the turned part is obtained when the spindle runs out due to uneven wear of its bearings or uneven wear of its journals.
5. Insufficient surface cleanliness during turning can be due to a number of reasons: high cutter feed, use of a cutter with incorrect angles, poor sharpening of the cutter, small radius of curvature of the cutter tip, high viscosity of the part material, vibration of the cutter due to a large overhang, insufficiently strong cutter attachment in the tool holder, increased gaps between individual parts of the support, vibration of the part due to its weak fastening or due to wear of the bearings and spindle journals.

All of the above reasons for marriage can be eliminated in a timely manner.

6. Burning of the hard center of the tailstock can be caused by the following reasons: the part is fixed too tightly between the centers; poor lubrication of the center hole; incorrect alignment of the workpiece; high cutting speed.
7. The discrepancy between the processing surfaces when turning on both sides in the centers is obtained mainly as a result of runout of the front center or the development of center holes in the workpiece. To prevent defects, it is necessary to check the condition of the center holes of the workpiece during finishing processing, and also ensure that there is no runout in the center of the headstock.

12. Safety precautions when turning cylindrical surfaces

In all cases of machining on lathes, it is necessary to pay attention to the strong fastening of the part and the cutter.

The reliability of fastening a part processed in centers largely depends on the condition of the centers. You cannot work with worn centers, since the part under the influence of the cutting force can be torn from the centers, fly to the side and injure the turner.

When processing parts in centers and chucks, the protruding parts of the clamp and chuck jaws often catch the worker’s clothing. These same parts can cause injury to your hands when measuring a part and cleaning the machine while moving. To prevent accidents, safety guards should be installed at the clamps or safety clamps should be used, and the jaw chucks should be protected. The perfect type of safety clamp is shown in Fig. 134. Rim 3 covers not only the head of the bolt 2, but also the pin 1 of the driving chuck.

To protect the turner’s hands and clothing from protruding parts of the chuck or faceplate, a special guard is used on modern lathes (Fig. 135). The casing 1 of the device is hingedly connected to a pin 2 fixed to the headstock body.

When installing parts in centers, you need to pay attention to the correctness of the center holes. If their depth is insufficient, the part may fall off the centers during rotation, which is very dangerous. In the same way, after securing the part in the chuck, you need to check whether the key is removed. If the key remains in the chuck, then when the spindle rotates it will hit the frame and fly off to the side. In this case, the machine may break down and the worker may be injured.

The cause of accidents is often chips, especially drain chips, which come off in a continuous ribbon at high cutting speeds. Such shavings should never be removed or torn off by hand; they can cause severe cuts and burns. Chip breakers should be used whenever possible. In extreme cases, when chip breaking is not achieved, it should be removed with a special hook.

When processing materials that produce short rebound chips, it is necessary to use safety glasses or use safety shields made of safety glass or celluloid (Fig. 136), attached to a hinged stand to the carriage. You need to sweep away small shavings resulting from processing brittle metals (cast iron, hard bronze) not with your hands, but with a brush.

Hand injuries may occur when installing and securing cutters as a result of the key being torn off the heads of the tool holder mounting bolts. The key breaks when the key jaws and bolt heads are worn out. Often, however, failure occurs because the turner uses a wrench whose size does not correspond to the size of the bolt.

Setting the cutter to the height of the centers using all sorts of non-suitable supports (metal scraps, pieces of hacksaws, etc.) does not ensure a stable position of the cutter during operation. Under the pressure of the chips, such pads are displaced, and the installation of the cutter becomes unstable. At the same time, the fastening of the cutter also weakens. As a result, the shims and the cutter can jump out of the tool holder and injure the lathe operator. In addition, when installing the cutter and when working on the machine, your hands may be injured by the sharp edges of the metal pads. Therefore, it is recommended that every turner have a set of backing blocks, varying in thickness, with well-processed supporting planes and edges.

Control questions 1. How to properly install the cutter in the tool holder?
2. How to check the position of the cutter tip relative to the center line?
3. How are parts installed and secured when turning cylindrical surfaces?
4. What is the difference between the operating conditions of the anterior and posterior centers?
5. How is the rotating center constructed and in what cases is it used?
6. How does the fluted front center work and what are its advantages?
7. How to check the correct installation of centers for turning a cylindrical surface?
8. How does a self-centering chuck work? Name its details, rules for installing and preparing it for work.
9. How to align a part when installing it in a four-jaw chuck?
10. What is the purpose of the cross feed screw dial?
11. What is the longitudinal feed dial used for? How is it built?
12. What are steady rests used for and in what cases are they used?
13. How does a fixed steady rest work?
14. How is the movable steady rest constructed?
15. How is the shaft blank prepared for installation in the steady rest?
16. Give an example of using a longitudinal stop; cross stop.
17. What types of defects are possible when turning cylindrical surfaces? How to eliminate the causes of marriage?
18. List the basic safety rules when turning cylindrical surfaces.

Lathes are used to process cylindrical parts. They include many varieties that differ in size and availability additional functions. Industrial models such as are very common and widely used in modern industry. In order for the device to function normally, you need to know all the features of its parts.

The lathe bed serves to secure almost all mechanisms and components that are used on this equipment. It is often cast from cast iron to create a massive and durable structure that can last a long time. This is due to the fact that it will be subject to heavy loads. You should also not forget about stability, since massive large models use enormous energy during operation and the base must resist the load well.

The machine bed and guides are attached with bolts to the stands or paired legs. If the device is short, then two racks are used. The longer it is, the more racks may be required. Most cabinets have doors, allowing them to be used as drawers. The guides should be treated with great care and avoided from being damaged. It is not advisable to leave tools, workpieces and other products on them. If you still have to place metal objects on them, then you should put a wooden lining before doing this. For better care, before each use of the machine, the frame must be wiped and lubricated. When the work is completed, shavings, dirt and other unnecessary objects should be removed from it.

The design features of the frame of metal-cutting machines may differ depending on the specific model, since they are designed for the convenient and safe placement of all equipment components. But the basic principles remain the same in many cases, so we can look at the basics using popular models as examples.

photo: construction of a cast iron bed

Longitudinal rib;
Longitudinal rib;
A transverse rib that serves to connect the longitudinal ribs;
Prismatic guides of longitudinal ribs;
Flat guides, which serve to install the tailstock and front headstock, as well as to move the caliper along them;

It is worth noting that the cross-section of the bed guides can have different shapes. A mandatory rule is to maintain a parallel arrangement, so that everything should be equidistant from the axis of the centers. This requires precise milling or planing. After this, the grinding and scraping operation is carried out. All this ensures precise processing of products, as well as eliminating problems with the movement of the caliper and the occurrence of shocks.

The bed of a metal lathe, which is shown in figure “a” under numbers 1 and 2, has a trapezoidal cross-section of guides. In this case, the main emphasis is on a large supporting surface. They have great wear resistance, which allows them to maintain their accuracy for a long time. At the same time, moving the caliper along them requires a lot of effort, especially if it is skewed.
Figure “b” shows a bed with a flat rectangular cross-section of guides. Unlike the previous one, they already have two stiffening ribs, rather than one, which makes them stronger.
Figure “c” shows a frame with triangular cross-section guides. Taking into account the fact that a fairly small supporting surface is used here, it is difficult to work with a large weight, so this type is used mainly for small machines.
Figure “d” shows a frame with a triangular cross-section and a supporting plane. In this case, it is also used for small-sized machines.

If the bed is intended for a heavy machine, then it has not only a large cross-section, but also greater bending resistance. One of the most common is the type shown in Figure “d”. Here the caliper carriage focuses on prism No. 3 in front, and rests on plane No. 6 at the rear. To prevent capsizing, it is held in place by plane No. 7. When tasking the direction, the main role is played by prism No. 3, especially since it absorbs most of the pressure exerted by the cutter.

If there is a recess on the frame near the headstock, then it is used to process large-diameter products. If the product is being processed, the radius of which is less than the height of the centers, then the recess is covered with a special bridge.

Lathe bed repair

Scraping a lathe bed is a technological process during which the bed is aligned to secure the feed box using a frame level. Thanks to this, it will be possible in the future to easily establish the perpendicularity of the mounting surface of the caliper and apron to the feed box.

First of all, install the frame on a rigid foundation and check the longitudinal direction along the surface level, and the transverse direction along the frame level. Permissible deviations are no more than 0.02 mm per 1 meter of product length.
Scrape the top surfaces of the guide, first on one side, using a paint straight edge. During this process, it is advisable to periodically check the alignment of the guides.
Then the surface of the second guide is scraped. Maximum tolerance The deviations here remain the same 0.02 mm per 1 meter of product length.

Grinding the lathe bed

Grinding a lathe bed consists of the following procedures:

It is necessary to clean and file away burrs and nicks existing on the surface;
The bed is installed on the table of the longitudinal planing machine and securely fixed there;
Next comes the check of the torsion of the guides, which is carried out using a level placed on the bridge of the tailstock;
During installation of the bed, a slight deflection of the product occurs, which should be corrected by making maximum contact with the table;
The curvature of the guides is re-checked so that the results coincide with what was before fastening;
Only after this do they begin to grind all contact surfaces of the product. The procedure is carried out using the end of a cup-shaped circle. its grain size should be K3 46 or KCh 46, and its hardness should correspond to SM1K.

Surface finishing by turning. Surface finishing on lathes Grinding on a lathe