I. Read the text about lathes and find answers to the following questions.

1. What are the oldest machine tools?

2. What operations can be performed on a lathe?

3. What are the main parts of the lathe?

4. How is metal removed from the workpiece in the lathe?

5. What provides cooling and lubrication of the lathe?

6. What type of lathes is used for individual part production?

7. What type of lathes is used for turning workpiece with large diameters?

Lathe is a machine tool that performs turning operations in which unwanted material is removed from a workpiece rotated against a cutting tool. Lathes are among the oldest and most important machine tools, used in France from 1569 and important in the Industrial Revolution in England, when they were adapted for metal cutting. Lathes (usually called engine lathes) today have a power-driven, variable-speed horizontal spindle to which the workholding device is attached. Operations include turning straight or tapered cylindrical shapes, grooves, shoulders, and screw threads and facing flat surfaces on the ends of cylindrical parts. Internal cylindrical operations include most of the common hole-machining operations, such as drilling, boring, reaming, counterboring, countersinking, and threading with a single-point tool or tap. Lathe is a machine tool for holding and turning metal, wood, plastic, or other material against a cutting tool to form a cylindrical product or part. It also drills, bores, polishes, grinds, makes threads, and performs other operations. Its principal parts are the headstock (attached to the bed or base of the machine), which holds one end of the material in a rotating spur; the tailstock, which holds the other end, moves along the bed, and can be clamped in position at any point; the cutting tool; and the power feed, comprising the drive and its motive parts.

There are a lot of varieties of lathes.

Lathes that sit on a bench or table are called “bench lathes”.

Lathes that do not have additional integral features for repetitive production, but rather are used for individual part production or modification as the primary role, are called “engine lathes”.

Lathes with a very large spindle bore and a chuck on both ends of the spindle are called “oil field lathes”.

Fully automatic mechanical lathes, employing cams and gear trains for controlled movement, are called screw machines.

Lathes that are controlled by a computer are CNC lathes.

Lathes with the spindle mounted in a vertical configuration, instead of horizontal configuration, are called vertical lathes or vertical boring machines. They are used where very large diameters must be turned, and the workpiece (comparatively) is not very long.

A lathe with a cylindrical tailstock that can rotate around a vertical axis, so as to present different facets towards the headstock (and the workpiece) are turret lathes.

Metalworking lathes

In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool, which is usually fixed to a solid moveable mounting called the “toolpost”, which is then moved against the workpiece using hand wheels and/or computer controlled motors.

The toolpost is operated by leadscrews that can accurately position the tool in a variety of planes. The toolpost may be driven manually or automatically to produce the roughing and finishing cuts required to turn the workpiece to the desired shape and dimensions, or for cutting threads, worm gears, etc. Cutting fluid may also be pumped to the cutting site to provide cooling, lubrication and clearing of chip from the workpiece. Some lathes may be operated under control of a computer for mass production of parts.

Text B

Grinding machine

I. Read the text about grinding machines and find answers to the following questions.

1. What is a grinding machine?

2. What are the main parts of a grinding machine?

3. How is material removed from the workpiece in the grinding machine?

4. What is the coolant used for?

Grinding machine is a machine tool used for grinding, which is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel’s surface cuts a small chip from the workpiece via shear deformation.

The grinding machine consists of a power driven grinding wheel spinning at the required speed which is determined by the wheel’s diameter and a bed with a fixture to guide and hold the work-piece. The grinding head can be controlled to travel across a fixed workpiece or the workpiece can be moved whilst the grind head stays in a fixed position. Very fine control of the grinding head or tables position is possible or using the features of NC or CNC controls.

Grinding machines remove material from the workpiece by abrasion, which can generate substantial amounts of heat; they therefore incorporate a coolant to cool the workpiece so that it does not overheat and go outside its tolerance. The coolant also benefits the machinist as the heat generated may cause burns in some cases. In very high-precision grinding machines (most cylindrical and surface grinders) the final grinding stages are usually set up so that they remove about 2/10000mm (less than 1/100000 in) per pass, this generates so little heat that even with no coolant, the temperature rise is small.

Text C

Milling Machine

I. Read the text about milling machine and find answers to the following questions.

1. What is a milling machine?

2. How does the rotating cutter move in the milling machine?

3. What operations can milling machines perform?

4. How can milling machines be operated?

A milling machine is a machine tool used for the shaping of metal and other solid materials. Its basic form is that of a rotating cutter which rotates about the spindle axis (similar to a drill), and a table to which the workpiece is attached. In contrast to drilling, where the drill is moved exclusively along its axis, the milling operation involves movement of the rotating cutter sideways as well as 'in and out'. The cutter and workpiece move relative to each other, generating a toolpath along which material is removed. The movement is precisely controlled, usually with slides and leadscrews or analogous technology. Often the movement is achieved by moving the table while the cutter rotates in one place, but regardless of how the parts of the machine slide, the result that matters is the relative motion between cutter and workpiece. Milling machines may be manually operated, mechanically automated, or digitally automated via CNC (computer numerical control).

Milling machines can perform a vast number of operations, some of them with quite complex toolpaths, such as slot cutting, planing, drilling, diesinking, rebating, routing, etc. Cutting fluid is often pumped to the cutting site to cool and lubricate the cut.

Part III

History of Machine Tools

You are going to read the text about history of machine tools. For questions 1-8 choose the answer (a, b, c or d) which you think fits best according to the text.

1. The birth of modern engineering industry is

a) the production of military devices.

b) the production of textile machines.

c) the manufacture of electrical devices.

d) the manufacture of metal cutting tools.

2. The use of metal in the production of machines was kept to a minimum

a) because of the lack of metal.

b) because of the lack of skilled craftsmen.

c) because it was difficult to manipulate metal.

d) because there were a lot of machine tools.

3. First machine tools appeared in

a) Japan

b) England

c) the USA

d) France

4. Why was not wood framing successful?

a) because it was difficult to change dimensions

b) because temperature and humidity did not change

c) because there were no skilled craftsmen

d) because of the lack of wood

5. How was metal first worked?

a) with animal power

b) with hammers, files, scrapers

c) with the help of electricity

d) with machine tools

6. What was the first large machine tool?

a) the milling machine

b) the shaping machine

c) the cylinder boring machine

d) the planing machine

7. What helped to develop machine tools in the 19-th century?

a) textile industry

b) military production

c) chemical industry

d) agriculture

8. Henry Maudslay was engaged in:

a) agriculture

b) textile industry

c) the Royal Navy

d) mechanical engineering

The Industrial Revolution could not have developed without machine tools, for they enabled manufacturing machines to be made. They have their origins in the tools developed in the 18th century by makers of clocks and watches and scientific instrument makers to enable them to batch-produce small mechanisms. The mechanical parts of early textile machines were sometimes called “clock work” because of the metal spindles and gears they used. The manufacture of textile machines drew craftsmen from these trades and is the origin of the modern engineering industry.

Machines were built by various craftsmen, carpenters made wooden framings, and smiths and turners made metal parts. A good example of how machine tools changed manufacturing took place in Birmingham, England, in 1830. The invention of a new machine by William Joseph Gillott, William Mitchell and James Stephen Perry allowed mass manufacture of cheap steel pen nibs; the process had been expensive. Because of the difficulty of manipulating metal and the lack of machine tools, the use of metal was kept to a minimum. Wood framing had the disadvantage of changing dimensions with temperature and humidity. As the Industrial Revolution progressed, machines with metal frames became more common, but they required machine tools to make them economically. Before the advent of machine tools, metal was worked manually using the basic hand tools of hammers, files, scrapers, saws and chisels. Small metal parts were readily made by this means, but for large machine parts, production was very laborious and costly.

Apart from workshop lathes used by craftsmen, the first large machine tool was the cylinder boring machine used for boring the large-diameter cylinders on early steam engines. The planing machine, the slotting machine and the shaping machine were developed in the first decades of the 19th century. Although the milling machine was invented at this time, it was not developed as a serious workshop tool until during the Second Industrial Revolution.

Military production had a hand in the development of machine tools. Henry Maudslay, who trained a school of machine tool makers early in the 19th century, was employed at the Royal Arsenal, Woolwich. He was engaged to build the machinery for making ships’ pulley blocks for the Royal Navy in the Portsmouth Block Mills. These were all metal and were the first machines for mass production and making components with a degree of interchangeability. The lessons Maudslay learned about the need for stability and precision he adapted to the development of machine tools, and in his workshops he trained a generation of men to build on his work, such as Richard Roberts, Joseph Clement and Joseph Whitworth. Roberts was a maker of high-quality machine tools and a pioneer of the use of jigs and gauges for precision workshop measurement.

Unit IV

METALS

Part I

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