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Such tools consist of a combination of cutting edges, all of which may be said to depend on each one; because if one breaks, the next in order will have a double duty to perform, and will soon follow鈥攁 reversal of the old adage, that 'union is strength,' [142] if by strength is meant endurance.

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A planing machine invented by Mr Bodmer in 1841, and since improved by Mr William Sellers of Philadelphia, is free from this elastic action of the platen, which is moved by a tangent wheel or screw pinion. In Bodmer's machine the shaft carrying the pinion was parallel to the platen, but in Sellers' machine is set on a shaft with its axis diagonal to the line of the platen movement, so that the teeth or threads of the pinion act partly by a screw motion, and partly by a progressive forward movement like the teeth of wheels. The rack on the platen of Mr Sellers' [134] machine is arranged with its teeth at a proper angle to balance the friction arising from the rubbing action of the pinion, which angle has been demonstrated as correct at 5°, the ordinary coefficient of friction; as the pinion-shaft is strongly supported at each side of the pinion, and the thrust of the cutting force falls mainly in the line of the pinion shaft, there is but little if any elasticity, so that the motion is positive and smooth..
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In no other branch of machinery has so much research and experiment been made during eighty years past as in steam machinery, and, strange to say, the greater part of this research has been directed to the details of engines; yet there has been no improvement made during the time which has effected any considerable saving of heat or expense. The steam-engines of fifty years ago, considered as steam-using machines, utilised nearly the same proportion of the energy or power developed by the boiler as the most improved engines of modern construction鈥攁 fact that in itself indicates that an engine is not the vital part of steam machinery. There is not the least doubt that if the efforts to improve steam-engines had been mainly directed to economising heat and increasing the evaporative power of boilers, much more would have been accomplished with the same amount of research. This remark, however, does not apply to the present day, when the principles of steam-power are so well understood, and when heat is recognised as the proper element to deal with in attempts to diminish the expense of power. There is, of course, various degrees of economy in steam-using as well as in steam-generating machinery; but so long as the best steam machinery does not utilise but one-tenth or one-fifteenth part of the heat represented in the fuel burned, there need be no question as to the point where improvements in such machinery should be mainly directed.?
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The commercial value of professional or technical knowledge is generally as the amount of time, effort, and unpaid labour that has been devoted to its acquirement. This value is sometimes modified by the exclusiveness of some branch that has been made the object of special study. Exclusiveness is, however, becoming exceptional, as the secrets of manufacture and special knowledge are supplanted by the application of general principles; it is a kind of artificial protection thrown around certain branches of industry, and must soon disappear, as unjust to the public and unnecessary to success..
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I think proper to point out these peculiarities, not so much from any importance they may have in themselves, but to suggest critical investigation, and to dissipate any preconceived opinions of forging being a simple matter, easy to learn, and involving only commonplace operations.
21 August, 2019 - 13:08
Same ! Who ever likes comics give me a reply
21 August, 2019 - 13:08
The best!