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    Software name: appdown
    Software type: Microsoft Framwork

    size: 818MB


    Software instructions

      In working to regular scales, such as one-half, one-eighth, or one-sixteenth size, a good plan is to use a common rule, instead of a graduated scale. There is nothing more convenient for a mechanical draughtsman than to be able to readily resolve dimensions into various scales, and the use of a common rule for fractional scales trains the mind, so that computations come naturally, and after a time almost without effort. A plain T square, with a parallel blade fastened on the side of the head, [80] but not imbedded into it, is the best; in this way set squares can pass over the head of a T square in working at the edges of the drawing. It is strange that a draughting square should ever have been made in any other manner than this, and still more strange, that people will use squares that do not allow the set squares to pass over the heads and come near to the edge of the board.Good fitting is often not so much a question of skill as of the standard which a workman has fixed in his mind, and to which all that he does will more or less conform. If this standard is one of exactness and precision, all that is performed, whether it be filing, turning, planing, or drawing, will come to this standard. This faculty of mind can be defined no further than to say that it is an aversion to whatever is imperfect, and a love for what [171] is exact and precise. There is no faculty which has so much to do with success in mechanical pursuits, nor is there any trait more susceptible of cultivation. Methodical exactness, reasoning, and persistence are the powers which lead to proficiency in engineering pursuits.

      This principle is somewhat obscure, and the nature of percussive forces not generally considereda matter which may be illustrated by considering the action of a simple hand-hammer. Few [103] people, in witnessing the use of a hammer, or in using one themselves, ever think of it as an engine giving out tons of force, concentrating and applying power by functions which, if performed by other mechanism, would involve trains of gearing, levers, or screws; and that such mechanism, if employed instead of a hammer, must lack that important function of applying force in any direction as the will and hands may direct. A simple hand-hammer is in the abstract one of the most intricate of mechanical agentsthat is, its action is more difficult to analyse than that of many complex machines involving trains of mechanism; yet our familiarity with hammers causes this fact to be overlooked, and the hammer has even been denied a place among those mechanical contrivances to which there has been applied the name of "mechanical powers."

      "Then, why did you want to stay at the man's house?what brought you here?"26

      At last I found an hotel, where I could have a small garret, against which arrangement I had not the slightest objection in the circumstances. The caf downstairs looked rather peculiar, with a great number of looking-glasses, and ladies with powdered faces. These seemed not averse to closer relations with me, but when I pretended not to understand a single word of French, they soon gave it up, and showed no further desire for my friendship. But I could see quite well that they discussed the question whether I was a German officer or a spy?This happened not only at Vis, but also at other places which I visited, more especially at Louvain. And those who read the following chapters carefully will find sufficient support for my opinion, that Belgium is innocent of the base charges and allegations uttered by Germany, which country soiled its conscience still worse, first by plunging the little kingdom into the direst misery, and then by accusing it falsely of crimes which it never committed.

      A carriage moving on angular ways always moves steadily and easily, without play in any direction until lifted from its bearing, which rarely happens, and its lifting is easily opposed by adjustable gibs. A carriage on a flat shear is apt to have play in a horizontal direction because of the freedom which must exist to secure easy movement. In the case of tracks, it may also be mentioned that the weight of a carriage acts as a constant force to hold it steady, while with a flat shear the weight of a carriage is in a sense opposed to the ways, and has no useful effect in steadying or guiding. The rigidity and steadiness of tool movement is notoriously in favour of triangular tracks, so much so that nearly all American machine tool-makers construct lathes in this manner, although it adds no inconsiderable cost in fitting.(1.) What kind of strains are shafts subjected to?(2.) What determines the strength of shafts in resisting transverse strain?(3.) Why are shafts often more convenient than belts for transmitting power?(4.) What is the difference between the strains to which shafts and belts are subjected?(5.) What is gained by constructing a line shaft of sections diminishing in size from the first mover?(6.) What is gained by constructing line shafts of uniform diameter?


      "Certainly, sister. Tell her that Bart of Uncle Henry is here." Again I was switched off, but the communication was this time restored after a few moments, and then I heard a joyful and surprised exclamation:My "foreign" passport was, of course, in French, of which language the man evidently knew not a word. Although I explained that this passport was the best one could get in The Netherlands, that I had paid six guilders and seventy-five cents for it, that I was a war-correspondent of De Tijd, it was all useless. I had to go with him to the guard-house, and the man kept the queer passportthe damning piece of evidencefirmly in his hand. All the inquisitive loafers, of which the frontier was full during those days, followed me, and so we went in procession to the guard-house, at some distance from the frontier. I heard all sorts of discussions behind me, and constantly caught words like: German, boche, deserter, franc-tireur, spy, and other complimentary niceties.


      CHAPTER XVI. MACHINERY OF APPLICATION.A second point to be noticed in hammers of this class is the nature of the connection with the driving power. In all cases there will be found an equivalent for the elastic helve of the trip-hammereither air cylinders, deflecting springs, or other yielding attachments,interposed between the crank and the hammer-head, also a slipping frictional belt or frictional clutches for driving, as in the case of trip-hammers.


      The tools employed for cutting screw threads constitute a separate class among the implements of a fitting shop, and it is considered best to notice them separately.In the same way the list went on for a goodly length, and he became actually angry when even then I refused to believe everything. He was especially pleased with the account of the victory near Libramont. He had a friend, also a physician, who had been compelled by the Germans to go with them in the medical service, and this friend had told him this himself. It was remarkable that educated, superior persons could become so narrow-minded in times like these, and believed anything simply because they hoped that it might be true.