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    Software name: appdown
    Software type: Microsoft Framwork

    size: 82MB

    Lanuage:Englist

    Software instructions

      Judged upon theoretical grounds, and leaving out the mechanical conditions of operation, it would at once be conceded that a proper plan would be to move the lightest body; that is, if the tools and their attachments were heavier than the material to be acted upon, then the material should be moved for the cutting action, and vice versa. But in practice there are other conditions to be considered more important than a question of the relative weight of reciprocating parts; and it must be remembered that in solving any problem pertaining to machine action, the conditions of operation are to be considered first and have precedence over problems of strain, arrangement, or even the general principles of construction; that is, the conditions of operating must form a base from which proportions, arrangements, and so on, must be deduced. A standard planing machine, such as is employed for most kinds of work, is arranged with a running platen or carriage upon which the material is fastened and traversed beneath the cutting tools. [130] The uniformity of arrangement and design in machines of this kind in all countries wherever they are made, must lead to the conclusion that there are substantial reasons for employing running platens instead of giving a cutting movement to the tools."No, no, sir," the lady said. "Oh, oh, it is so terrible! By and by the Germans will burn Lige and kill us all. She is the little daughter of my brother at Maastricht, and came to visit us a few days before war broke out, but now she will be killed too, for she refuses to go away."


      "Oh, go on!" I answered. "I don't think that I need fear anything of the kind. I am in any case a Netherlander!"By what accident had I not been disturbed? The height, perhaps, at which my miserable little garret-room was situated.


      That is not evidence however, for how did they get the information? From my own experience I make bold to say with the greatest confidence that these reports came from German sources only, whereas there was not any ground for them.

      Forging as a process in machine-making includes the forming and shaping of the malleable parts of machinery, welding or joining pieces together, the preparation of implements for forging and finishing, tempering of steel tools, and usually case-hardening.

      Leaving out problems of mechanism in forging machines, the adaptation of pressing or percussive processes is governed mainly by the size and consequent inertia of the pieces acted upon. In order to produce a proper effect, that is, to start the particles of a piece throughout its whole depth at each blow, a certain proportion between a hammer and the piece acted upon must be maintained. For heavy forging, this principle has led to the construction of enormous hammers for the performance of such work as no pressing machinery can be made strong enough to execute, although the action of such machinery in other respects would best suit the conditions of the work. The greater share of forging processes may be performed by either blows or compression, and no doubt the latter process is the best in most cases. Yet, as before explained, machinery to act by pressure is much more complicated and expensive than hammers and drops. The tendency in practice is, however, to a more extensive employment of press-forging processes.The terrible thunder of the guns, of both besiegers and besieged, vibrated through the air. In the distance I noticed a couple of men, probably German soldiers, but a pontoon-bridge was nowhere to be seen. After a few minutes, however, I reached a spot where the Meuse makes a short curve, and had scarcely walked round it, when I saw, only a couple of hundred yards away, the bridge in question, across which a long train of vehicles was passing, loaded with victuals, hay, straw, etc.


      Upon entering a shop the first thing to be done is to gain the confidence and the respect of the manager or foreman who has charge of the work; to gain such confidence and respect is different from, and has nothing to do with, social relations and must depend wholly upon what transpires in the works. To inspire the confidence of a friend one must be kind, faithful, and honourable; but to command the confidence of a foreman one must be punctual, diligent, and intelligent. There are no more kindly sentiments than those which may be founded on a regard for industry and earnest effort. A learner may have the misfortune to break tools, spoil work, and fail in every [167] way to satisfy himself, yet if he is punctual, diligent, and manifests an interest in the work, his misfortunes will not cause unkind resentment.

      2. The capacity of shafts is governed by their strength and the speed at which they run taken together.

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      CHAPTER XII. BELTS FOR TRANSMITTING POWER.

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      Already from a distance with much fuss they signalled to me to stop, and of course I obeyed at once. Two men dismounted, came to me in a perfect rage, and, without asking who I was or what I was doing, cut my tyres to pieces in several98 places; they abused me with wild gesticulations and threats, jumped on their horses, and rode off. I dragged my wretched vehicle with its stabbed tyres a little distance, but then met a second patrol, who showed still greater indignation, and destroyed it altogether.In the case of tools composed partly of iron and partly of steel, steel laid as it is called, the tendency to crack in hardening may be avoided in most cases by hammering the steel edge at a low temperature until it is so expanded that when cooled in hardening it will only contract to a state of rest and correspond to the iron part; the same result may be produced by curving a piece, giving convexity to the steel side before hardening.

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      General engineering work cannot consist in the production of duplicate pieces, nor in operations performed constantly in the same manner as in ordinary manufacturing; hence there has been much effort expended in adapting machines to general purposesmachines, which seldom avoid the objections of combination, pointed out in a previous chapter.


      alllittle