Text 3 machine-tools (1656)

Before metal is formed into the required shape, it has to undergo a number of processes, such as casting, rolling, forging, welding, piercing, trimming, spinning, bending, drawing, etc. The machines which work on the surface of the metal piece, or provide it with grooves or holes or with a thread, are called machine-tools.

The most common machine-tool found in almost any workshop is the lathe, in which the job spins round its axis while a cutting tool is working on it. Its main parts are: the headstock, which usually contains the gearing mechanism: the chuck, into which the job is clamped; the tailstock, which can be moved along the bed to adjust the distance between the chuck and the tailstock centre; and the carriage consisting of the saddle and the cross slide on which the toolholder with the tool is mounted. The speed at which the lathe turns can be adjusted either by regulating the speed of the motor driving it, or by the gearing. The automatic turret lathe is a perfection of the ordinary lathe. Its tools are changed automatically. A worker skilled in the use of a lathe is cabled a turner.

Other machine-tools work on plane surfaces, for example milling machines, and also planing and shaping machines. A broaching machine employs broaches to make non-circular holes. Circular holes are drilled by a drilling machine or bored by a boring machine or a boring mill. Gear cutting machines include gear milling machines, hobbing machines, gear shapers and gear grinding machines. Thread milling machines are used in the production of threads on shafts and on other machine elements; whilst die-sinking machines turn out dies, which are used in the process of stamping.

All these machines use cutting tools, usually made of high-speed steel; grinding machines, on the other hand, use abrasives such as diamonds, diamond dust, corundum, silicon carbide, etc. Honing and lapping machines also use abrasives; they enable us to obtain a smooth finish of less than 0.001 mm.

Text 4 lathes

Our machine-tool manufacturing works produce engine lathes of heavy, medium and light types. The maximum diameter of workpieces turned over the bed varies from 320 to 4000 mm.

Brief specifications of some lathe models are given below:

	Model designation
	1A616	1K62	163	1A64	165	1660	1670	1680
Maximum work size over bed, mm Distance between centres, mm Spindle speed range, r. p. m. Weight of lathe, t (metric)	320 710 33 to 2367 1.45	400 710 1000 1400 12.5 to 2000 2.1 2.3 2.4	630 1400 2800 10 to 1250 4 4.6	800 2800 7.5 to 750 11.8	1000 2800 5000 5 to 500 12.5 16.0	1250 8000 3.15 to 200 55.4	1600 8000 2.5 to 160 126	2000 10000 2 to 128 137

The models listed above do not include the full variety of lathe types and sizes.

So, for instance, a special model Л-220 laboratory lathe with a centre height of 350 mm and a distance between centres of 1 500 mm can be successfully applied for miscellaneous research work such as investigating the dynamics of the cutting process, or determining the endurance of tungsten carbides and other cutting tools.

A most convenient and efficient machine is the model combination lathe for turning, milling, drilling, grinding, slotting, and tool-sharpening jobs. It can be used both in stationary and mobile repair shops, on ships, etc.

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