IX. Describe the construction and principle of operation of the contracting chuck shown in Fig. 30.

11. Holding work in a vice

Vices are attachments which are mainly used for holding workpieces in machine and fitting shops. It should be noticed that a vice may also be used as an attachment for holding workpieces on a metal-cutting lathe.

Depending on the character of operation performed bench vices or parallel vices may be applied. Bench vices are made from forged steel and are of rugged construction. If their construction were not rugged, they could not be used when heavy-duty operations such as cutting, riveting, etc. are performed. A bench vice consists of two jaws: the movable jaw and the solid jaw. At the end of the solid jaw there is a lug for securing the vice to a bench. The extension rod of the jaw is built-in a wooden pillow. When a workpiece is clamped between the jaws they are moved together by means of a square-threaded screw. By unscrewing the screw the jaws are moved apart by a spring riveted to the solid jaw. In parallel vices the jaws move parallel to each other. It should be pointed out that parallel vices in their turn are subdivided into swivel vices and plain vices.

Fig. 31. Swivel Vice:

a — front view; b — cross-sectional view; 1 — vice base*; 2 — solid jaw, 3 — movable jaw; 4 — screw; 5 — fixed nut; 6 — handle; 7 — swivel plate; 8 — spindle; 9 — bolt; 10 — lever

A swivel vice (Fig. 31), being the most convenient vice in operation, consists of a vice base,* a solid jaw and a movable jaw. The motion of the movable jaw is provided by the rotation of a screw inserted into a fixed nut. When the screw is rotated by means of a handle the former will screw in and move the movable jaw to the workpiece to be clamped. The vice base is mounted on a swivel plate being connected with the latter by a spindle. A bolt is inserted into a T-groove. By turning a handle the bolt may be loosened and the vice may be turned in a desired direction.

Plain vices differ entirely from swivel vices in the absence of the swivel plate and that the vice base is bolted directly to a bench. The vice of such a type is made from grey iron, steel hardened plates with a nut being screwed to its jaws. Parallel vices are convenient for clamping workpieces, but as their jaws are of little strength they are non-suitable for heavy-duty operations.

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^*American — vice ground

Exercises

I. Translate the following words and phrases from the text:

vices, attachment, bench vice, to rivet, rugged, parallel vices, heavy-duty operation, to secure, movable jaw, solid jaw, lug, pillow, extension rod, swivel vices, plain vices, front view, cross-sectional view, fixed nut, to loosen

II. Answer the following questions:

1. What are vices and what purposes are they used for? 2. On what lathes are vices used? 3. Depending on what features may bench or parallel vices be applied for holding workpieces? 4. What material are vices made of? 5 What main parts does a bench vice consist of? 6. Why is the end of the solid jaw of the bench vice provided with a lug? 7. How do plain vices differ from swivel vices?

III. Find in the text English equivalents of:

тиски, вид спереди, проекция поворотных тисков в поперечном разрезе, поворотная плита, пружина, основание, завинчивать, неповоротные тиски, тавровый или Т-образный паз, закрепленная гайка, поворачивать, обеспечивать, приспособление

IV. Underline the suffixes and prefixes and translate into Russian the following words:

attachment, mainly, operation, movable, wooden, convenient, unscrew, disconnect, extension, rugged, performed

V. Translate the following sentences, paying attention to different meanings of should and would:

1. It is necessary that all fitting shops should be supplied with bench vices. 2. If the jaws of parallel vices had not been of low strength, the parallel vices would have found greater application in industry 3. It is very important that work-pieces being in the process should be firmly clamped in vices. 4. If fitting shops were not supplied with vices, how would workers clamp workpieces? 5. It is necessary that the vice should be fastened to a bench. 6. Great attention should be paid to the proper securing of the vice to the bench. 7. Providing all the requirements were met, the efficiency of the swivel vices would be increased. 8. If the bolt had been loosened enough, we should have been able to turn the swivel vices in a desired direction.