7) Grinding machine

A grinding machine is a machine tool used for producing very fine finishes or making very light cuts, using an abrasive wheel as the cutting device. This wheel can be made up of various sizes and types of stones, diamonds or of inorganic materials.

The grinding machine consists of a power driven grinding wheel spinning at the required speed (which is determined by the wheel’s diameter and manufacturer’s rating, usually by a formula) and a bed with a fixture to guide and hold the workpiece. The grinding head can be controlled to travel across a fixed work piece or the workpiece can be moved whilst the grind head stays in a fixed position.

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. 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 negligible.

I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.

II. Find the following word-combinations in English in the text: ріжучий пристрій; що обертається на необхідній швидкості; направляти та тримати заготовку; охолоджувати заготовку; високоточні.

8) From the history of a lathe

The lathe is an ancient tool, dating at least to the Egyptians and, known and used in Assyria, Greece, the Roman and Byzantine Empires.

The origin of turning lathe dates to around 1300BC when the Egyptians first developed a two-person lathe. One person would turn the wood work piece with a rope while the other used a sharp tool to cut shapes in the wood. The Romans improved the Egyptian design with the addition of a turning bow. Early bow lathes were also developed and used in Germany, France and Britain. In the Middle Ages a pedal replaced hand-operated turning, freeing both the craftsman’s hands to hold the woodturning tools. The pedal was usually connected to a pole, often a straight-grained sapling. The system today is called the “spring pole” lathe. Spring pole lathes were in common use into the early 20^th Century. A two-person lathe, called a “great lathe”, allowed a piece to turn continuously (like today’s power lathes). A master would cut the wood while an apprentice turned the crank.

During the industrial revolution the lathe was motorized, allowing wooden turned items to be created in less time and allowing the working of metal on a lathe. The motor also produced a greater rotational speed, making it easier to quickly produce high quality work. Today most commercial lathes are computer-operated allowing for mass-production that can be created with accurate precision and without the cost of employing craftsmen.

I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.

II. Find the following words and word-combinations in English in the text: обертати дерев’яну заготовку за допомогою мотузки; дуга, що обертається; інструменти для обертання дерева; обертатися безперервно; створюватися за менший проміжок часу; обробка металу на токарному верстаті; більша швидкість обертання; швидко виготовляти високоякісну деталь; витрати пов’язані з найманням майстрів.