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【提案议案】吉林省政协委员隋利国:推进职业教育和产业发展同频共振 促进吉林经济繁荣发展

类型:奇幻地区:莫桑比克剧发布:2020-11-25 13:44:14

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As to the practical results which may be attained by a gauging system, it may be said that they are far in advance of what is popularly supposed, especially in Europe, where gauges were first employed.CHAPTER XVIII. MACHINE COMBINATION.

These are but a few of many influences which tend to irregular cooling, and are described with a view of giving a clue from which other causes may be traced out. The want of uniformity in sections which tends to irregular cooling can often be avoided without much loss by a disposition of the metal with reference to cooling strains. This, so far as the extra metal required to give uniformity to or to balance the different sides of a casting, is a waste which engineers are sometimes loth to consent to, and often neglect in designs for moulded parts; yet, as before said, the difficulty of irregular cooling can in a great degree be counteracted by a proper distribution of the metal, without wasting, if the matter is properly understood. No one is prepared to make designs for castings who has not studied the subject of cooling strains as thoroughly as possible, from practical examples as well as by theoretical deductions.

One of the peculiarities of trip-hammers as machines is the mechanical difficulties in connecting them with the driving power, especially in cases where there are a number of hammers to be driven from one shaft.

CHAPTER XXXII. SLOTTING MACHINES.The general theory of their action may be explained in the following propositions:鈥

The EndINTRODUCTION.

As remarked in a previous place, no one can expect to prepare successful designs for machinery, who does not understand the details of its construction; he should know how each piece is moulded, forged, turned, planed, or bored, and the relative cost of these processes by the different methods which may be adopted.It is common to use a flat point for draughting pencils, but a round one will often be found quite as good if the pencils are fine, and some convenience is gained by a round point for free-hand use in making rounds and fillets. A Faber pencil, that has detachable points which can be set out as they are worn away, is convenient for draughting.

Flat or plane joints nearly always admit of adjustment between the fitted surfaces; that is, the material scraped or ground away in fitting can be compensated by bringing the pieces nearer together; but parallel cylindrical joints cannot even be tried together until finished, consequently, there can be nothing cut away in trying them together. Tapering, or conical joints, can of course be trial-fitted, and even parallel fits are sometimes made by trial, but it is evident that the only material that can [149] be cut away in such cases, is what makes the difference between a fit too close, and one which will answer in practice.Our text-books, such as are available for apprentices, consist mainly of mathematical formul? relating to forces, the properties of material, examples of practice, and so on, but do not deal with the operation of machines nor with constructive manipulation, leaving out that most important part of a mechanical education, which consists in special as distinguished from general knowledge.

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This article has been introduced, not only to give a true understanding of the effect and value of machine combination, but to caution against a common error of confounding machine combination with invention.

CHAPTER XXIX. FITTING AND FINISHING.(1.) How may the arrangement of an establishment affect its earnings?鈥(2.) Why is the arrangement of engineering establishments generally irregular?鈥(3.) Why should an erecting shop be a base of arrangement in engineering establishments?鈥(4.) What are the principal materials consumed in engineering works?鈥(5.) Why is not special experience a safe guide in forming plans of shop arrangement?

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