TOPIC 13. MACHINING PROCESSES

Text 1

1.Обратите внимание на перевод следующих слов и словосочетаний:

lathe - токарный станок;

jaw chucks - кулачковый патрон;

reaming - расширение;

taper turning - точение конических поверхностей;

knurling - накатка.

 

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LATHE MACHINE

Lathe is an important and widely used machine tool used in the machining process. Sometimes it is called as mother of all other machine tools. The main function of the lathe machine is to remove excess material from the job and give it require size and dimensions. Lathe rotates the work piece about an axis. The job is inserted between the jaw chucks of lathe and then turning operation is done by a single point cutting tool. The excess material s removed by the single point cutting tool in the form of chips. Work piece is fixed in jaws and rotates about their axis. Feed is provided to the cutting tool as per requirement. Rotation is provided to the work piece by electric motor or engine at specific rpm. By using lathe we can perform various operations like drilling, turning, reaming, boring, taper turning, knurling, thread cutting and grinding etc.

These days we use different types of lathe according to our requirement. Lathes are manufactured in different types and sizes; lathe can be very small in size for small operations to huge in sizes used for turning large diameter shafts. All lathes which we used have almost same function and operations. Following are the different types of lathe we use in industry as per requirements.

 

Text 2

 

1.Обратите внимание на перевод следующих слов и словосочетаний:

engine lathe - токарно-винторезный станок;

centre lathe - центровой токарный станок;

bed - станина;

headstock -     головка;

tailstock - упор, натяжное устройство;

gear - зубчатая передача;

belt drive - ремённой привод;

speed lathe - быстроходный токарный станок;

feed mechanism - подающий механизм;

bench lathe - верстачный токарный станок, настольный токарный станок;

tool room lathe - инструментальный станок;

limit gauge - ограничительный калибр;

turret lathe - токарно-револьверный станок;

turret - револьверный супорт;

automatic lathe - автоматический токарный станок;

wheel lathe - колесотокарный станок;

gap bed lathe - токарный станок с выемкой в станине;

duplicate lathe - сдвоенный станок;

T-lathe - лоботокарный станок.

 

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TYPES OF LATHE MACHINE

 Centre or engine lathe is oldest and very common type of lathe. It is widely used machine tool in industry and its main function is to manufacture cylindrical profiles. The basic parts of the centre lathe are bed, headstock and tailstock. It has durable headstock and that can drive the lathe at different speeds with the help of some mechanisms. In very early days when no electric motor used this was driven by steam engines that’s why it is called as engine lathe also but now days power is transmitted to lathe by electric motors with the help of some gears and belt drives. We can adjust the speed of lathe by using gears and belt drives. Engine lathes can easily feed the cutting tool in both directions i.e. longitudinal and lateral directions with the help of feed mechanisms.

 Speed lathe works at very high speed as name suggest. Its headstock spindle is rotates at very high speed. Speed lathe is very simple and basic type of lathe having basic parts like bed, headstock, tailstock but it has no feed mechanism. Feed is provided by manually of hand operated. This type of lathe is used where less cutting force is required or we can say that it is used to machine soft materials. It is used for spinning, centering, polishing and machining of wood etc.

 Bench lathe is mounted on a bench. It is generally a small type of lathe. It has also same parts like headstock, tail stock and can perform same functions as engine lathe but mainly used for working on small and precious parts.

 Tool room lathe works on different ranges of speeds it can be operates on high rpm as well as low rpm as per requirements. Its parts are almost same similar to engine lathe but the parts are built very accurately and should be arranged in proper sequence because this lathe is used for highly precious work with very less tolerances. Tool room lathes are used for precious work on tools where dimensional accuracy should be maintained, dies, limit gauges and machining of those parts which requires more accuracy with minimum tolerances.

 Turret lathe is the modified version of engine lathe. It is an example of advancement of technology in manufacturing industry. Older lathes have some draw back i.e. they cannot use in mass production and can performs only single operation at a time but after the invention of turret lathe we can easily do mass production. Construction of turret lathe is similar to engine lathe but difference is the tail stock of an engine lathe is replaced by a hexagonal turret on which multiple tools are fitted. These tools are capable in performing multiple tasks like turning, boring, thread cutting, drilling and facing. By using these tools we can easily perform different type of operations on a single work piece without changing of tool and work piece.

 Automatic lathe works automatically. Standard lathes have some draw backs i.e. they are not used for mass production. But automatic lathes are used for mass production. Some mechanisms are responsible for the automation in it. In fully automatic lathes the job handling and tool changing is automatic but in semiautomatic tool changing is done manually but job handling movements are automatic. These types of lathes are high speed and heavy duty.

   Computerized controlled lathes are widely used lathe in present time because of its working. It is most advance type of lathe this time. CNC is the example of this kind of lathes. CNC stands for Computerized numerically controlled. These lathes are fully automatic can works on some programs feed into the computer or we can say that it uses computer programs to control the machine tool. Once the program is feed in to the computer a large number of parts of same kind can be machined with very high speed and accuracy. Pre-programmed computer software is responsible for the all process from tool changing to replacing new work piece with old one all functions done automatically. A semi-skilled worker can easily operate this after initial setup is done. These types of lathes are used for mass production. Components manufactured by these lathes are very accurate in dimensional tolerances.

 These types of lathes are used for some special purposes as per their name. These are used to machine those components which cannot be machined by standard lathes. The types of lathe which comes in this category are wheel lathe, gap bed lathe, tracer/duplicate lathe and T-lathe.

Wheel lathe is used for machining of journals and rail rods. It is also used for turning the threads on locomotive wheels.

Gap bed lathe is used to machine large diameter work piece i.e. up to 1.5 to 2 meters and 6-8 meters in length.

T-shape lathe is used to machine rotors used in jet engines and gas turbines. The shape of its bed in T that’s why it is called as T-shaped lathes.

Duplicate or tracer lathe is used for duplicating or making replica of the shape. This lathe can machine different type of contours. It traces the shape of one component and makes a replica of same contour. Numerically controlled lathes

are the modified version of Duplicate lathes.

 

Text 3

 

1.Обратите внимание на перевод следующих слов и словосочетаний:

bed - стол (станка);

сarriage  - супорт;

cross-slide - вертикальный суппорт;

compound rest - верхний суппорт;

tool post - резцедержатель;

apron - фартук (станка);

facing - защитная облицовка;

lead screw - ходовой винт;

headstock - передняя бабка (станка);

pulleys - ролик;

V-belts - клиновидный приводной ремень;

spindle - вал;

set of gears - набор зубчатых колёс;

tailstock - натяжное устройство;

reamer - развёртка;

tailstock quill - пиноль задней бабки;

feed rod - ходовой валик;

friction clutch - муфта трения;

keyway - кнопочный паз;

chip pan - стружкосборник;

split nut - обхватная гайка.

 

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LATHE COMPONENTS

Bed. The bed supports all major components of the lathe. Beds have a large mass and are built rigidly, usually from gray or nodular cast iron. The top portion of the bed has two ways with various cross sections that are hardened and machined for wear resistance and dimensional accuracy during turning. In gap-hed lathes, a section of the bed in front of the headstock can be removed to accommodate larger diameter workpieces.

Carriage. The carriage, or carriage assembly, slides along the ways and consists of an assembly of the cross-slide, tool post, and apron. The cutting tool is mounted on the tool post, usually with a compound rest that swivels for tool positioning and adjustment. The cross-slide moves radially in and out, controlling the radial position of the cutting tool in operations such as facing. The apron is equipped with mechanisms for both manual and mechanized movement of the carriage and the cross-slide by means of the lead screw.

Headstock. The headstock is fixed to the bed and is equipped with motors, pulleys, and V-belts that supply power to a spindle at various rotational speeds. The speeds can be set through manually controlled selectors or by electrical controls. Most headstocks are equipped with a set of gears, and some have various drives to provide a continuously variable range of speed to the spindle. Headstocks have a hollow spindle to which work-holding devices are mounted and long bars or tubing can be fed through them for various turning operations. The accuracy of the spindle is important for precision in turning, particularly in high-speed machining; preloaded tapered or ball bearings typically are used to rigidly support the spindle.

Tailstock. The tailstock, which can slide along the ways and be clamped at any

position, supports the other end of the workpiece. It is equipped with a center that

may be fixed (dead center), or it may be free to rotate with the workpiece (live

center). Drills and reamers can be mounted on the tailstock quill (a hollow cylindrical part with a tapered hole) to drill axial holes in the workpiece.

Feed Rod and Lead Screw. The feed rod is powered by a set of gears through the headstock. The rod rotates during the lathe operation and provides movement to the carriage and the cross-slide by means of gears, a friction clutch, and a keyway along the length of the rod. Closing a split nut around the lead screw engages it with the carriage; the split nut is also used for cutting threads accurately.

 

Text 4

 

1.Обратите внимание на перевод следующих слов и словосочетаний:

boring - растачивание;

facing - защитная облицовка;

chamfering - закругление;

boring bar - шпиндель расточного станка (выдвижной);

bore - отверстие (образованное сверлом);

chatter - нестабильная вибрация;

boring mill - токарно-карусельный станок;

milling cutter - фрезерный резец.

 

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BORING AND BORING MACHINES

Boring enlarges a hole made previously by some other process or produces circular internal profiles in hollow workpieces. The cutting tools are similar to those used in turning and are mounted on a boring bar to reach the full length of the bore. The boring bar must be sufficiently stiff to minimize tool deflection and thus maintain dimensional accuracy and avoid vibration and chatter. For this reason, a material with a high elastic modulus (such as tungsten carbide) is desirable. Boring bars have been designed and built with capabilities for damping vibration.

Boring operations on relatively small workpieces can be carried out on lathes; large workpieces are machined on boring mills. These machine tools are either horizontal or vertical and are capable of performing various operations, such as turning, facing, grooving, and chamfering. In horizontal boring machines, the

workpiece is mounted on a table that can move horizontally in both the axial and radial directions. The cutting tool is mounted on a spindle that rotates in the headstock, which is capable of both vertical and longitudinal movements. Drills, reamers, taps, and milling cutters also can be mounted on the machine spindle.

A vertical boring mill is similar to a lathe, has a vertical axis of workpiece rotation, and can accommodate workpieces with diameters as much as 2.5 m.

The cutting tool is usually a single point, made of M2 or M3 high-speed steel or P10 (C7) or P01 (CS) carbide. It is mounted on the tool head, which is capable of vertical movement (for boring and turning) and radial movement (for facing), guided by the cross-rail. The head can be swiveled to produce conical (tapered) holes. Cutting speeds and feeds for boring are similar to those for turning.

Boring machines are available with a variety of features. Machine capacities

range up to 150 kW and are available with computer numerical controls, allowing

all movements of the machine to be programmed. Little operator involvement is required, and consistency and productivity are improved.

 

Text 5

 

1.Обратите внимание на перевод следующих слов и словосочетаний:

drilling machines - сверлильный станок;

tapping - нарезание резьбы;

ream - рассверлить;

drill press -     вертикально-сверлильный станок;

adjustable table - перестанавливаемый стол (в станке);

vise -     зажимное приспособление;

handwheel - маховик (ручной);

counterboring - рассверливание.

 

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DRILLING MACHINES

 Drilling machines are used for drilling holes, tapping, reaming, and small-diameter boring operations. The most common machine is the drill press. The workpiece is placed on an adjustable table, either by clamping it directly into the slots and holes on the table or by using a vise, which in turn is clamped to the table. The drill is lowered manually by a handwheel or by power feed at preset rates. Manual feeding requires some skill in judging the appropriate feed rate.

 Drill presses usually are designated by the largest workpiece diameter that can be accommodated on the table and typically range from 150 to 1250 mm. In order to maintain proper cutting speeds at the cutting edges of drills, the spindle speed on drilling machines has to be adjustable to accommodate different drill sizes. Adjustments are made by means of pulleys, gearboxes, or variable-speed motors.

 The types of drilling machines range from simple bench-type drills used to drill small-diameter holes to large radial drills, which can accommodate large workpieces. The distance between the column and the spindle center can be as much as 3 m. The drill head of universal drilling machines can be swiveled to drill holes at an angle. Developments in drilling machines include numerically controlled three-axis machines, in which the operations are performed automatically and in the desired sequence with the use of a turret. Note that the turret holds several different drilling tools.

 Drilling machines with multiple spindles (gang drilling) are used for high-production-rate operations. These machines are capable of drilling, in one cycle, as many as 50 holes of varying sizes, depths, and locations. They also are used for reaming and counterboring operations. However, with advances in machine tools, gang-drilling machines are now being replaced with numerical-control turret drilling machines. Special drilling machines, such as those which produce holes in continuous hinges (piano hinges), use twist drills 1 mm in diameter. These machines usually are horizontal and produce holes in up to 3-m long segments in one cycle.

 Workholding devices for drilling are essential to ensure that the workpiece is

located properly. They also keep the workpiece from slipping or rotating during

drilling. Workholding devices are available in various designs; the important features are three-point locating for accuracy and three-dimensional work

holding for secure fixtures.

 

Text 6

 

1.Обратите внимание на перевод следующих слов и словосочетаний:

milling machine - фрезерная машина;

knee milling machine - консольно-фрезерный станок;

planer-type milling machine - продольно-фрезерный станок;

rotary-table machine  - станок с поворотным столом.

 

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MILLING MACHINES

Because they are capable of performing a variety of cutting operations, milling machines are among the most versatile and useful machine tools. The first milling machine was built in 182.0 by Eli Whitney (1765-1825). A wide selection of milling machines with numerous features is now available. The features of typical standard milling machines are described next. Note, however, that many of these machines and operations are now being replaced with computer controls and machining centers. Inexpensive, manually controlled machines are still widely used, especially for small production runs.

Plain milling machines have three axes of movement, with the motion usually imparted manually or by power. In universal column-and-knee milling machines, the table can be swiveled on a horizontal plane. In this way, complex shapes (such as helical grooves at various angles) can be machined to produce parts such as gears, drills, taps, and cutters.

Bed-type Milling Machines. In bed-type machines, the worktable is mounted directly on the Cutters bed, which replaces the knee and can move only longitudinally. These machines are Spindle Carrier not as versatile as other types, but they have high stiffness and typically are used for high-workpiece production work. The spindles may be horizontal or vertical and of duplex or triplex types (with two or three spindles, respectively), for the simultaneous machining of two or three workpiece surfaces.

Several other types of milling machines are available. Planer-type milling machines, which are similar to bed-type machines, are equipped with several heads and cutters to mill different surfaces. They are used for heavy workpieces and are more efficient than simple planers when used for similar purposes.

Rotary-table machines are similar to vertical milling machines and are equipped with one or more heads for face-milling operations.

Milling machines have been rapidly replaced by computer numerical-control (CNC) machines for all but the lowest production quantities. These machines are versatile and capable of milling, drilling, boring, and tapping with repetitive accuracy. Also available are profile milling machines, which have five axes of movement; note the three linear and two angular movements of the machine components.

 

Text 7

1.Обратите внимание на перевод следующих слов и словосочетаний:

capstan lathe - револьверный станок;

turret lathe - токарно-револьверный станок;

turret - револьверный супорт;

saddle - поворотная платформа;

ram - поршень;

feed stop screws - упор для автоматического выключения подачи.

 

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DIFFERENCE BETWEEN CAPSTAN AND TURRET LATHE

Capstan and turret lathes are semiautomatic lathes. Semiautomatic means machining is done automatically but some other functions like changing of job/work piece and setting of tools are done manually. These are the modified version of engine lathe. It is an example of advancement of technology in manufacturing industry. Construction of turret/capstan lathes is similar to engine lathe but difference is they have an axially movable index able turret having hexagonal shape in place of tail stock on which multiple tools are fitted. These tools are capable in performing multiple tasks like turning, boring, thread cutting, drilling and facing. By using these tools we can easily perform different type of operations on a single work piece without changing of tool and work piece. All these tools are mounted on a hexagonal turret; turret is rotates after each operation. Turret lathe is used for mass production and the advantage of this lathe is a less skilled operator can perform work on it once all setup is done properly. These types of lathes can be used for machining large work piece also. These lathes are relatively costlier than engine lathe because of their complex construction. Using these lathes a single type of job can be easily repetitive manufacture with less effort and time or we can say that both the lathes are used for mass production.

Both turret and capstan lathes are similar in construction, operation and in some applications also but the major differences between them are as follow:

 

	Turret lathe	Capstan lathe
1	In turret lathe the main turret is directly installed on the saddle and the saddle is move along the entire length of the lathe bed.	Capstan lathe is ram type turret lathe and the movement of the ram is limited.
2	In turret lathe the turret tool head is directly mounted on the saddle and they appear like a single unit.	Turret head is mounted on a slide called as ram which is mounted on the saddle in case of capstan lathes.
3	In turret lathe saddle is moved for providing feed to the tool.	But in case of capstan lathe saddle is fixed at a point but ram is moved.
4	Saddle is move along the entire length so it is used to machining of large work pieces.	The short strokes of the ram have some limitations so this lathe is used to machining of small work piece only.
5	It has slower operation because of heavy weight of all the components.	It has fast working operations because lighter in construction.
6	In turret lathe limit dogs are used to control the movement of the tool.	In case of capstan lathe feed stop screws are provided at the rear side of the turret for controlling the tool movement.
7	It is used to machine large work piece so large depth of cut and feed is provided for machining.	Relatively less feed and depth of cut are provided for machining because used for small work pieces.
8	In turret lathes external threads are generally cut by a single point or a multipoint chasing tool which is installed on the front slide and moved by a short lead screw and a swing type half nut.	But in case of capstan lathe external threads are cut using a self-opening die which is mounted on the one face of the turret.
9	Turret lathe is mostly single spindle and horizontal type lathe but may be vertical and multi spindle type in some cases.	But the capstan lathe is usually single spindle and horizontal axis type only.
10	In turret lathes power operated jaw chucks are used to hold the work piece.	In case of capstan lathe hand operated collect chucks are used for holing the work piece.

 

ЛИТЕРАТУРА

1) Долматовская Е.Ю. Изобретения и изобретатели: учеб.-справ. пособие для изучющих англ.яз. – М.:АСТ:Астрель; Владимир: ВКТ, 2008. – 128с.:ил.

2) Парахина А.В. Пособие по переводу технических текстов с английского языка на русский: Для сред.спец.учеб. заведений.- 2-е изд., испр. – М.: Высш. школа, 1979. – 160с.:ил.

 3) Смекаев В. П. Учебник технического перевода (английский язык).

Н. Новгород: НГЛУ им Н.А. Добролюбова, Вектор ТиС, 2006. — 316 с.

4) Macmillan Guide to Science: Student's Book. - Oxford :

Macmillan   Publishers   limited, 2008. - 127 p. : il.

5) Manufacturing engineering and technology. Serope Kalpakjian.

  Steven R.  Schmid. – Pearson, 2014 Professional English in use.

6) Engineering: Student's Book. – Cambridge  University   Press, 2009. – 144p.: il.

 

Интернет-ресурсы

7) Universe Today            www.universetoday.com

8) Design & Technology     http://www.bbc.co.uk

9) History                         http://www.bbc.co.uk

10) Production Engineering   http://www.mech4study.com