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ENGLISH 三上悠亚2019番号5月A difficulty which arises in hardening tools is because of the contraction of the steel which takes place in proportion to the change of temperature; and as the time of cooling is in proportion to the thickness or size of a piece, it follows, of course, that there is a great strain and a tendency to break the thinner parts before the thicker parts have time to cool; this strain may take place either from cooling one side first, or more rapidly than another.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,  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.
(1.) What limits the speed at which the reciprocating parts of machines may act?(2.) What is the nature of reciprocal motion produced by cranks?(3.) Can reciprocating movement be uniform in such  machines as power-hammers, saws, or pumps?(4.) What effect as to the rate of movement is produced by the elastic connections of a trip-hammer?Disintegrating machines, such as are employed for pulverising various substances, grinding grain or pulp, separating fibrous material, and so on, are, with some exceptions, simple enough to be readily understood. One of these exceptions is the rotary "disintegrators," recently introduced, about the action of which some diversity of opinion exists. The effect produced is certainly  abrasive wear, the result of the pieces or particles striking one against another, or against the revolving beaters and casing. The novelty of the process is in the augmented effect produced by a high velocity, or, in other words, the rapidity of the blows."What do you want with him?"
The End"No!"Many soldiers, probably most of them, were undoubtedly of good faith, and believed what they related; but the damnable notion had been put into their heads by their superiors. That is why I do not consider it impossible that some places were wrecked on account of alleged acts by francs-tireurs.
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The most effectual means of securing a uniform effect from a tempering bath is by violent agitation, either of the bath or the piece; this also adds to the rapidity of cooling.Drilling, more than any other operation in metal cutting, requires the sense of feeling, and is farther from such conditions as admit of power feeding. The speed at which a drill may cut without heating or breaking is dependent upon the manner in which it is ground and the nature of the material drilled, the working conditions may change at any moment as the drilling progresses; so that hand feed is most suitable. Drilling machines arranged with power feed for boring should have some means of permanently disengaging the feeding mechanism to prevent its use in ordinary drilling.
In respect to lathe manipulation, which is perhaps the most difficult to learn of all shop operations, the following hints are given, which may prove of service to a learner: At the beginning the form of tools should be carefully studied; this is one of the great points in lathe work; the greatest distinction between a thorough and indifferent latheman is that one knows the proper form and temper of tools and the other does not. The adjustment and presenting of tools is soon learned by experience, but the proper form of tools is a matter of greater difficulty. One of the first things to study is the shape of cutting edges, both as to clearance below the edge of the tool, and the angle of the edge, with reference to both turning and boring, because the latter is different from turning. The angle of lathe tools is clearly suggested by diagrams, and there is no better first lesson in drawing than to construct diagrams of cutting angles for plane and cylindrical surfaces.A true movement of carriages is dependent upon the amount or wearing power of their bearing surface, how this surface is disposed in reference to the strain to be resisted, and the conditions under which the sliding surfaces move; that is, how kept in contact. The cutting strain which is to be mainly considered, falls usually at an angle of thirty to forty degrees downward toward the front, from the centre of the lathe. To resist such strain a flat top shear presents no surface at right angles to the strain; the bearings are all oblique, and not only this, but all horizontal strain falls on one side of the shear only; for this reason, flat top shears have to be made much heavier than would be required if the sum of their cross section could be employed to resist transverse strain. This difficulty can, however, be mainly obviated by numerous cross girts, which will be found in most lathe frames having flat tops.
"Why not, sir?" I asked.(1.) Why are machine frames constructed in sections, instead of being in one piece?(2.) Why must parts which have contact on opposite sides have specific dimensions?(3.) What are standards of measure based upon in England, America, and France?(4.) How can weight be measured by time?(5.) Has the French metre proved a standard admitting of test reference?"S?ur Eulalie!... S?ur Eulalie!... You ... you ... are a ... cousin ... of ... S?ur Eulalie?"
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Machines are composed of parts connected together by rigid and movable joints; rigid joints are necessary because of the expense, and in most cases the impossibility, of constructing framing and other fixed detail in one piece.A pendulum vibrating in uniform time regardless of distance, but always as its length, if arranged to perform one vibration in a given time, gave a constant measure of length. Thus lineal measure comes from time; cubic or solid measures from lineal measure, and standards of weight from the same source; because when a certain quantity of a substance of any kind could be determined by lineal measurement, and this quantity was weighed, a standard of weight would be reached, provided there was some substance sufficiently uniform, to which reference could be made in different countries. Such a substance is sea or pure water; weighed in vacuo, or with the air at an assumed density, water gives a result constant enough for a standard of  weight.
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