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    Software name: appdown
    Software type: Microsoft Framwork

    size: 832MB

    Lanuage:Englist

    Software instructions

      There is but little object in preparing designs, when their counterparts may already exist, so that in making original plans, there should be a careful research as to what has been already done in the same line. It is not only discouraging, but annoying, after studying a design with great care, to find that it has been anticipated, and that the scheme studied out has been one of reproduction only. For this reason, attempts to design should at first be confined to familiar subjects, instead of venturing upon unexplored ground.


      With running dies, blanks may be clamped when a machine is in motion, and as the blank does not revolve, it may, when long, be supported in any temporary manner. The dies can be opened and closed by the driving power also, and no stopping of a machine is necessary; so that several advantages of considerable importance may be gained by mounting the dies in a running head, a plan which has been generally adopted in late years by machine tool makers both in England and America.


      2. The necessity for, and consequent saving effected by, power-machinery for handling is mainly in vertical lifting, horizontal movement being easily performed by hand.In a meadow east of the city I saw three big guns mounted, the biggest I had seen as yet. They kept up a continuous and powerful cannonade at the forts near the town, that had not yet been taken. There were three of them left, of which Loncin was the most important.

      The variation of dimensions which are sensible to the touch at one ten-thousandth part of an inch, furnishes an example of how important the human senses are even after the utmost precision attainable by machine action. Pieces may pass beneath the cutters of a milling machine under conditions, which so far as machinery avails will produce uniform sizes, yet there is no assurance of the result until the work is felt by gauges.

      Machine motion is mainly rotary; and as rotary motion is accomplished by cylindrical parts such as shafts, bearings, pulleys and wheels, we find that the greater share of machine tools are directed to preparing cylindrical forms. If we note the area of the turned, bored and drilled surface in ordinary machinery, and compare with the amount of planed surface, we will find the former not less than as two to one in the finer class of machinery, and as three to one in the coarser class; from this may be estimated approximately the proportion of tools required for operating on cylindrical surfaces and plane surfaces; assuming the cutting tools to have the same capacity in the two cases, the proportion will be as three to one. This difference between the number of machines required for cylindrical and plane surfaces is farther increased, when we consider that tools act continually on cylindrical surfaces and intermittently on plane surfaces.


      A common angular-pointed drill is capable of withstanding a greater amount of strain upon its edges, and rougher use than any other cutting implement employed in machine fitting. The rigid support which the edges receive, and the tendency to press them to the centre, instead of to tear them away as with other tools, allows drills to be used when they are imperfectly shaped, improperly tempered, and even when the cutting edges are of unequal length.

      "And how are they thanked for it?

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      CHAPTER XXXVIII. GAUGING IMPLEMENTS.The next morning at six I was out and about again. I had not been able to get any breakfast, for the people themselves had nothing. The Germans had called at all the hotels and shops requisitioning everything in stock to feed the thousands who had invaded Lige like so many locusts. The inhabitants practically starved during those days, and carefully saved up bits of bread already as hard as bricks. It was a good thing that the night before I had eaten something at the nunnery, for although at a shop I offered first one, and later on two francs for a piece of bread, I could not get any.

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      On the hot afternoon of August 7th, 1914, the much-delayed train rumbled into the station at Maastricht. A dense mass stood in front of the building. Men, women, and children were crowded there and pushed each other weeping, shouting, and questioning. Families and friends tried to find each other, and many of the folk of Maastricht assisted the poor 16creatures, who, nervously excited, wept and wailed for a father, for wife and children lost in the crowd. It was painful, pitiful, this sight of hundreds of fugitives, who, although now safe, constantly feared that death was near, and anxiously clutched small parcels, which for the most part contained worthless trifles hurriedly snatched up when they fled.A finisher's engine lathe consists essentially of a strong inflexible shear or frame, a running spindle with from eight to sixteen changes of motion, a sliding head, or tail stock, and a sliding carriage to hold and move the tools.

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      Let the reader compare a hammer with a wheel and axle, inclined plane, screw, or lever, as an agent for concentrating and applying power, noting the principles of its action first, and then considering its universal use, and he will conclude that, if there is a mechanical device that comprehends distinct principles, that device is the common hammer. It seems, indeed, to be one of those provisions to meet a human necessity, and without which mechanical industry could not be carried on. In the manipulation of nearly every kind of material, the hammer is continually necessary in order to exert a force beyond what the hands may do, unaided by mechanism to multiply their force. A carpenter in driving a spike requires a force of from one to two tons; a blacksmith requires a force of from five pounds to five tons to meet the requirements of his work; a stonemason applies a force of from one hundred to one thousand pounds in driving the edge of his tools; chipping, calking, in fact nearly all mechanical operations, consist more or less in blows, such blows being the application of accumulated force expended throughout a limited distance.


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