2. Metal-cutting and locksmith's cutting tools

Metal cutting differs from-chipping in substituting im­pact stresses by pressing forces in this operation. Cutting is used for separating some part from a piece of metal as well as to cut angles, grooves and pipes. Depending upon the shape and size of workpieces cutting is done by means of different cutting tools such as pliers, bench-shears, alligator shears, hack saws and pipe-cutters made of carbon steel.

Fig. 4. Pliers:

1 – cutting jaw; 2 – handle

Pliers, or wire-cutters (Fig. 4) are used for cutting thin wire. Pliers consist of two cutting jaws and two handles.A piece of wire is placed between the cutting jaws and the wire is cut by exerting pressure on the handles of the pliers.

Fig. 5. Bench-Shears:

1— shear blade; 2 — handle

Bench shears are made of steel. Lateral surfaces of shear blades are hardened, sharpened and ground.

Bench-shears (Fig. 5) are provided with two handles one of which is at a right angle to the other and fixed on a bench. The length of the handle is 400-800 mm, while that of the cutting part is 100-300 mm. The material is cut by pressing on one of the handles.

Fig. 6 Hack Saw

1 — frame: 2 — toothed blade

A hack saw (Fig. 6) is used for cutting thick metal sheets, bars, round-shaped material, etc. The hack saw consists of a frame and a long toothed blade made of tool carbon steel. The teeth on the blade are hardened. The blades with different pitches have different applications, the pitch of the blade depending on the material to be sawed. The thinner the material to be handled, the finer must be

Fig. 7. Alligator Shears:

1 - bed; 2 — bedplate; 3 — arm; 4 — cutting blade; 5 — electromotor; 6 — machine vice

the pitch of the blade used for sawing this material, and vice versa.

Fig. 7 shows alligator shears which is a heavy duty machine) for cutting materials of large sections such as pipes, beams, auto frames, axles and different types of industrial scrap. The alligator shears consist of cast iron bed 1 and bedplate 2. Arm 3 is mounted on the bedplate. Cutting blade 4 is fixed within the arm. Electromotor 5 imparts reciprocating motion to the arm and the, blade. The workpiece to be cut is clamped in machine vice 6.

Special pipe-cutters (Fig. 8) serve for cutting pipes. The pipe-cutter consists of body 1, handle 4, and three steel cutting rollers. Two rollers 2 installed on the fixed axles of the body and roller 3 installed on the axle of the handle may revolve and cut a pipe fixed in a special pipe fixture. For this purpose the pipe-cutter is turned round the pipe to be cut, pressing the cutting rollers against its surface.

Fig. 8. Pipe-Cutters:

1- body; 2 – rollers; 3 – roller; 4 - handle

Exercises

I. Use the following words and phrases in sentences of your own:

bedplate, arm, pitch, bar, lateral, metal cutting tools, pliers, pipe-cutters, hack saw, cutting jaws, to harden, right angle, bench-shears, to press, bed, industrial scrap, groove, to impart, reciprocating motion, to install, fixture, body

II. Supply the missing words:

1. The p… of a blade is the distance from the point of one t… to the point of the next t… .2. This pitch is expressed by the number of t... per one inch of the

b… length. 3. The hand hack saw blade is a thin blade with teeth formed on one e… . 4. The flexible h... s... blade is used for s...ing tin, copper, aluminium and other soft met­als. 5. Cutting is done by means of different c... t... . 6. For cutting wire such cutting t... as p... are used. 7. One handle of b...-s... is at a r... a... to the other.

III. Translate the following sentences into English using the infinitive instead of the attributive clauses:

Example: Материал, который нужно разрезать, зажимает­ся в тисках.

The metal to be cut is clamped in the vice.

1.Шаг полотна ножовки зависит от материала, кото­рый будет распиливаться, 2. Различные виды стали, ко­торые используются для полотна ножовок, изготовляются на нашем заводе. 3. Полотно ножовки, которое надо ис­пользовать для распиливания этих тонких листов, должно иметь 32 зуба на один дюйм. 4. Труба, которую надо раз­резать труборезом, будет закреплена в специальном при­способлении. 5. При вращении трубореза вокруг изделия, которое надо разрезать, создается режущее усилие.

IV. Make up questions to which the italicized words are the answers:

1. This bar is subjected to the action of two sets of exter­nal forces. 2. Cutting is used in cases when it is necessary to separate a piece of metal. 3. Thin wire is cut with pliers. 4. Sheets of metal are cut with bench-shears. 5. Cutting tools are made of carbon steel: 6. Pliers consist of two cutting jaws and two handles.

V. Giving the answers to the following questions describe the principle of operation of pliers, bench-shears, and alli­gator shears and pipe-cutter shown in Figs 4, 5, 7, and 8:

1. What are pliers used for? 2. What do the pliers con­sist of? 3. What is the funtcion of pliers, jaws and handles? 4. What material are bench-shears made of? 5. What are the bench-shears provided with? 6. What purposes are alli­gator shears used for? 7. What principal parts do the alliga­tor shears consist of? 8. What part of the alligator shears is the arm mounted on? 9. Where is the cutting blade of the alligator shears fixed? 10. What motion does the electro­motor impart to the arm and the blade? 11. What purpose are pipe-cutteres used for? 12. What parts does a pipe-cutter: consist of? 13. How is the cutting performed? 14. Where is the-pipe fixed for cutting?