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, either a toolpost or a turret, which is then moved against the workpiece using handwheels and/or computer controlled motors. The cutting tools come in a wide range of sizes and shapes depending upon their application. Some common styles are diamond, round, square and triangular.

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 swarf from the workpiece. Some lathes may be operated under control of a computer for mass production of parts.

Manually controlled metalworking lathes are commonly provided with a variable ratio gear train to drive the main leadscrew. This enables different thread pitches to be cut. On some older lathes or more affordable new lathes, the gear trains are changed by swapping gears with various numbers of teeth onto or off of the shafts, while more modern or expensive manually controlled lathes have a quick change box to provide commonly used ratios by the operation of a lever. СNС lathes use computers and servomechanisms to regulate the rates of movement.

Milling machines exist in two basic forms: horizontal and vertical, which terms refer to the orientation of the cutting tool spindle. Unlike a drill press, in which the workpiece is held stationary and the drill is moved vertically to penetrate the material, milling also involves movement of the workpiece against the rotating cutter, the latter of which is able to cut on its flanks as well as its tip. Workpiece and cutter movement are precisely controlled to less than 0,001 inches (025 millimeters), usually by means of precision ground slides and leadscrews or analogous technology. Milling machines may be manually operated, mechanically automated, or digitally automated via computer numerical control (CNC).

Milling machines can perform a vast number of operations, some very complex, such as slot and keyway cutting, planning, drilling, diesinking, rebating, routing, etc. Cutting fluid is often pumped to the cutting site to cool and lubricate the cut, and to sluice away the resulting swarf.

Speaking:

I. Divide the text into some meaningful parts, giving them the proper title,

II. Render the text, using the following phrases:

1. as far as I know from the text…

2. it is known that…

3. it is necessary to note…

4. the text under discussion is about…

5. the most important thing is…

6. it is possible to tell…

7. the procedure of metal cutting involves…

Text III Welding Processes Read the text telling about the various types of welding:

shielded metal arc welding		дуговая сварка защищенным металлическим электродом
manual metal arc welding		ручная дуговая сварка металлическим электродом
stick welding		сварка с применением стержня
сonsumable electrode		расходный электрод
flux		флюс, шлак
to suit		подходить, годиться
residue		остаток
offcast iron		некондиционный чугун
flux-cored arc welding		дуговая сварка флюсом
submerged arc welding		дуговая сварка в погруженной среде
to stick (stuck, stuck)		держаться, оставаться, застревать