一道本在线影像免一区二

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    Software name: appdown
    Software type: Microsoft Framwork

    size: 27MB

    Lanuage:Englist

    Software instructions

      CHAPTER X


      Chasing produces screws true with respect to their axis, and is the common process of threading all screws which are to have a running motion in use, either of the screw itself, or the nut.For disadvantages there is, on the other hand, a want of uniformity in fittings that prevents their interchange from one part of a line shaft to the othera matter of great importance, as such exchanges are frequently required. A line shaft, when constructed with pieces of varying diameter, is special machinery, adapted to some particular place or duty, and not a standard product that can be regularly manufactured as a staple article by machinists, and thus afforded at a low price. Pulleys, wheels, bearings, and couplings have all to be specially prepared; and in case of a change, or the extension of lines of shafting, cause annoyance, and frequently no little expense, which may all be avoided by having shafts of uniform diameter. The bearings, besides being of varied strength and proportions, are generally in such cases placed at irregular intervals, and the lengths of the different sections of the shaft are sometimes varied to suit their diameter. With line shafts of uniform diameter, everything pertaining to the shaftsuch as hangers, couplings, pulleys, and bearingsis interchangeable; the pulleys, wheels, bearings, or hangers can be placed at pleasure, or changed from one part of the shaft to another, or from [47] one part of the works to another, as occasion may require. The first cost of a line of shafting of uniform diameter, strong enough for a particular duty, is generally less than that of a shaft consisting of sections varying in size. This may at first seem strange, but a computation of the number of supports required, with the expense of special fitting, will in nearly all cases show a saving.


      "Not at all! If you step outside, you can see them standing, ten minutes from here. Near Lixhe they threw a bridge across the Meuse. It is the third already which they put down, for each time they are smashed from the fort. Oh, it is horrible; there must surely fall a number of dead, and here we have seen corpses in the Meuse already.... But I do not understand how you ventured to come here...."

      The dust-wall extended gradually as the distance grew covered by the Germans in their flight to their former positions. But at last we saw the first men emerge in complete disorder from that driving cloud. Some on the right, others on the left, here60 and there also small groups which courageously dragged their guns with them, as they saved themselves from that infernal downpour."3. Grgoire, permanent deputy.

      They behaved tolerably well during the first few days after the occupation of Tongres; but that did not last long, and soon they began here also to commit atrocious acts of terrorism. One evening96 at about the middle of August several civilians were killed, a dozen houses along the road to Maastricht were fired, and in the town the windows of several shops smashed, which was followed by general looting. That lost them whatever sympathy they might have met with in the district.


      A moment later a gigantic motor-car came racing down at a great speed. Six soldiers stood up in it, their rifles pointed at me. I thought that they36 intended to shoot me and everybody they might meet, but a seventh soldier standing by the side of the chauffeur made a movement with his arms, from which I understood that he wanted me to put my hands up. I did so.

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      First. By combining two or more operations in one machine, the only objects gained are a slight saving in first cost, one frame answering for two or more machines, and a saving of floor room.In front of me, behind me, on all sides, the guns boomed, clouds of dust and smoke filled the air, making it impossible to see much, which made the awe and terror endurable; but after the air became clear again, and the sun shed glowing light on the beautiful fields, it was terrible to think that all those dots in the plain were the bodies of young men, cruelly crushed by the infernal products of human ingenuity. It was agony to see here and there a body rising up, merely to fall down again immediately, or an arm waving as if invoking help.

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      4. The speed at which shafts should run is governed by their size, the nature of the machinery to be driven, and the kind of bearings in which they are supported.

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      A proof of this last proposition is found in the fact that a thorough latheman will perform nearly as much work and do it as well on an old English lathe with plain screw feed, as can be performed on the more complicated lathes of modern construction; but as economy of skill is sometimes an equal or greater object than a saving of manual labour, estimates of tool capacity should be made accordingly. The main points of a lathe, such as may most readily affect its performance, are firsttruth in the bearings of the running spindle which communicates a duplicate of its shape to pieces that are turned,second, coincidence between the line of the spindle and the movement of the carriage,third, a cross feed of the tool at a true right angle to the spindle and carriage movement,fourth, durability of wearing surfaces, especially the spindle bearings and sliding ways. To these may be added many other points, such as the truth of feeding screws, rigidity of frames, and so on, but such requirements are obvious.Politeness is as indispensable to a learner in a machine shop as it is to a gentleman in society. The character of the courtesy may be modified to suit the circumstances and the person, but still it is courtesy. An apprentice may understand differential calculus, but a workman may understand how to bore a steam cylinder; and in the workman's estimation a problem in calculus is a trivial thing to understand compared with the boring of a steam engine cylinder. Under these circumstances, if a workman is not allowed to balance some of his knowledge against politeness, an apprentice is placed at a disadvantage.


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