6.5. Machine Tools Classification

At the present time the machine-tool industry produces a large number of metal-cutting machine-tools different in purpose, processing capacities, degree of automatization and size. According to domestic classification, all machine tools are divided into ten main groups depending upon the type of processing operation they perform or tools they employ:

0-reserve group; 1-lathes; 2-drilling and boring machines; 3-grinding and microfinishing machines; 4-combination machine tools; 5-gear-and-thread-cutting machines; 6-milling machines; 7-planers, shapers, slotters and broaching machines; 8-cutting-off machines; 9-miscellaneous.

Each main group, in turn, is further divided into ten subgroups. For example, for lathes we have: 0-special, 1-automatic and semiautomatic single-spindle, 2-automatic and semiautomatic multiple-spindle, 3-turret lathes and so on.

Each subgroup is subdivided into some type, size and modification classes, or sub-subgroups. For example, 1K62 is specified:

1-machine tool of lathe group engine turning, threadcutting and facing lathe;

6-engine and facing lathe (subgroup);

2-maximum radius of work is 200 mm (size class);

K-modification.

But, basic model of the 1K62 engine lathe has the following modifications: model IK62A with tracer control, model 1K62B, which is the same model but of higher accuracy, model 1K62T, which is a high-precision lathe, model lK62ПУ with numeral controls and so on.

6.6. Lathe Works

The lathe is a machine tool that holds work between centers or in a chuck while it is rotated against a fixed tool to form a surface of revolution, e.g. cylindrical, conical and contoured surfaces.

Besides the basic operations of turning, facing, boring, drilling, threading, etc., the lathe can also do milling, shaping, gear cutting, fluting and grinding. Any other machine tool cannot perform such a variety of operations. For continuous or heavy-duty work a specialized machine tool is recommended for these secondary operations.

The Fig. 6.4 represents the simplified scheme of the model 1K62. The principal parts of the lathe machine 1K62 are: bed with two legs 1 and 15, headstock 2, tailstock 14, carriage 7 and chuck 6 on spindel. The speed gearbox 5 is driven through V-belts from electrical motor housed in the left leg 1 of the bed.

Fig. 6.4. Engine lathe: 1, 15 – legs; 2 – headstock; 3 – teed gear box; 4 – V-belts transmission;

5 – speed gear box; 6 – chuck; 7 – carriage; 8 – sledge; 9 – turning tool-holder;

10 – support; 11 – apron; 12, 13 – screws; 14 – tailstock

Thanks to combination of 26 gears the spindel and chuck 6 with a workpiece have variable rotation speed.

Before starting any work the work piece must be clamped with a chuck 6, when it has small length, or with the chuck and center of tailstock 14, when it is long enough (l>3d). The tool-holder 9 is mounted on support 10, which may perform 4 motions (Fig. 6.4 and 6.5):

- longitudinal S_L together with carriage 7 along slide bars;

- crossing one S_S;

- revolving one S_r;

- inclined to spindel axis S inc (Fig. 6.5k).

The tailstock moves manually on slide bars and its center has longitudinal motion by manual wheel. Instead of center the drill or the reamer may be installed.

In the headstock the feed gear box 3 is placed. It revolves screw 13, which moves carriage and special chisel when thread is cut. Longitudinal and crossing motions of support 10 with chisel may be carried out manually by wheels or by power drive and screw 12.

Figure 6.5 shows workpieces upon which numerous operations have been done. A study of this illustration will give some indications as to why different tools are used for turning (a), facing (b), necking and parting (c), drilling (d), boring (e), threading (f), forming (g), tapering (h, k).

Fig. 6.5. Cutting operation used in lathe work: a – turning; b – facing; c – necking or parting;

d – drilling; e – boring; f – threading; g – forming; h, k – tapering

Tools are classified according to their designated purpose (operations), location of the main cutting edge (right - hand and left-hand), shape and material of the blade, etc.

A lathe can be used for drilling and boring. The process is called drilling, when a hole is to be cut in a solid work piece. In the lathe the drill is inserted into the tailstock sleeve.

Drilled holes or integrally cast holes of castings are frequently bored to the finished size (Fig. 6.6).

Fig. 6.6. Cutting inside contours: a – a face; b – a conic surface