• sitemap?RBoxL.xml
  • sitemap?CT7gC.xml
  • sitemap?7Eaqg.xml
  • sitemap?jmakl.xml
  • sitemap?V46xs.xml
  • sitemap?uprgt.xml
  • sitemap?KFVMK.xml
  • sitemap?uRTwU.xml
  • sitemap?q9ej6.xml
  • loading
    Software name: appdown
    Software type: Microsoft Framwork

    size: 500MB

    Lanuage:Englist

    Software instructions

      It is not the intention to discuss patent law, nor even to estimate what benefits have in the past, or may in the future, be gained to technical industry by the patent system, but to impress engineering apprentices with a better and more dignified appreciation of their calling than to confound it with chance invention, and thereby destroy that confidence in positive results which has in the past characterised mechanical engineering; also to caution learners against the loss of time and effort too often expended [161] in searching after inventions.Considered upon grounds of commercial expediency as a question of cost alone, it is generally cheaper to move material by hand when it can be easily lifted or moved by workmen, when the movement is mainly in a horizontal direction, and when the labour can be constantly employed; or, to assume a general rule which in practice amounts to much the same thing, vertical lifting should be done by motive power, and horizontal movement for short distances performed by hand. There is nothing more unnatural than for men to carry loads up stairs or ladders; the effort expended in such cases is one-half or more devoted to raising the weight of the body, which is not utilised in the descent, and it is always better to employ winding or other mechanism for raising weights, even when it is to be operated by manual labour. Speaking of this matter of carrying loads upward, I am reminded of the fact that builders in England and America, especially in the latter country, often have material carried up ladders, while in some of the older European countries, where there is but little pretension to scientific manipulation, bricks are usually tossed from one man to another standing on ladders at a distance of ten to fifteen feet apart.


      The extreme nicety with which gauging implements are fitted seems at first thought to be unnecessary, but it must be remembered that a cylindrical joint in ordinary machine fitting involves a precision almost beyond the sense of feeling, and that any sensible variation in turning gauges is enough to spoil a fit.This mode of reasoning will lead to proper estimates of the difference in value between good tools and inferior tools; the results of performance instead of the investment being first considered, because the expenses of operating are, as before assumed, usually ten times as great as the interest on the value of a machine.


      A drilling machine, adapted to the usual requirements of a machine fitting establishment, consists essentially of a spindle arranged to be driven at various speeds, with a movement for feeding the drills; a firm table set at right angles to the spindle, and arranged with a vertical adjustment to or from the spindle, and a compound adjustment in a horizontal plane. The simplicity of the mechanism required to operate drilling tools is such that it has permitted various modifications, such as column drills, radial drills, suspended drills, horizontal drills, bracket drills, multiple drills, and others.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.

      The terrified little sister was unable to stammer anything more, and in great fear suddenly closed the little shutter again.(1.) Describe the different modifications of screw-cutting machines.(2.) What is gained by revolving the dies instead of the rod?(3.) What is gained by expanding dies?(4.) What is the difference between screws cut by chasing and those cut on a screw-cutting machine?


      We waited in the street for two of the soldiers who went to fetch the old man. After waiting a good while the poor wretch appeared between them. He wept profusely, and between his loud sobs affirmed repeatedly that he was innocent, that he did not know me, that I told him I was a Netherland journalist, and so on, and so on: "Oh, gentlemen!oh, gentlemen!" he exclaimed, "I must not leave my little boy ... my laddie; ... he is quite alone.... Oh, let me go!" ...

      Two soldiers now took everything I had in my pockets, even my watch and my purse. This brought also to light a German map of Belgium, with a stamp "For military use only." I was told in a gruff voice that this was a highly suspicious thing, and that they could not understand how it got into my possession. I replied quite coolly that I had bought the thing in Aix-la-Chapelle for one mark, where it could be had in many shops, and that the words "For the military only" merely revealed the shrewd German commercial instinct, which knows that people always like to possess things which are not meant for them.

      downloads

      [160]

      downloads

      The feed adjustment of the tool being intermittent and the amount of cutting continually varying, this movement should be performed by hand, so as to be controlled at will by the sense of feeling. The same rule applies to the adjustment of the rack for spacing; being intermittent and irregular as to time, this movement should also be performed by hand. The speed of the cutting movement is known from ordinary practice to be from sixteen feet to twenty feet a minute, and a belt two and a half inches wide must move two hundred feet a minute to propel an ordinary metal cutting tool, so that the crank movement or cutter movement must be increased by gearing until a proper speed of the belt is reached; from this the speed of intermediate movers will be found.

      downloads


      I have in this way imperfectly indicated a methodical plan of generating a design, as far as words alone will serve, beginning with certain premises based upon a particular work to be performed, and then proceeding to consider in consecutive order the general character of the machine, mode of operation, movements and adjustments, general arrangement, strains, special arrangement, and proportions.At that dinner I also made the acquaintance of Professor Nerincx, the acting burgomaster. It was a courageous act to assume the government of the town destroyed by the Germans; he did it for the sake of his fellow-citizens, who will never be able to requite their indebtedness to the temporary burgomaster for what he did for them; and most of them do not even know it.


      alllittle