FORE:Cutting, as a process in converting material, includes the force to propel cutting edges, means to guide and control their action, and mechanism to sustain and adjust the material acted upon. In cutting with hand tools, the operator performs the two functions of propelling and guiding the tools with his hands; but in what [58] is called power operations, machines are made to perform these functions. In nearly all processes machines have supplanted hand labour, and it may be noticed in the history and development of machine tools that much has been lost in too closely imitating hand operations when machines were first applied. To be profitable, machines must either employ more force, guide tools with more accuracy, or move them at greater speed, than is attainable by hand. Increased speed may, although more seldom, be an object in the employment of machinery, as well as the guidance of implements or increased force in propelling them. The hands of workmen are not only limited as to the power that may be exerted, and unable to guide tools with accuracy, but are also limited to a slow rate of movement, so that machines can be employed with great advantage in many operations where neither the force nor guidance of tools are wanting.
Saturday, 23/08/2014
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FORE:It is never enough to know that any piece of work is commonly constructed in some particular manner, or that a proposition is generally accepted as being correct; a reason should be sought for. Nothing is learned, in the true sense, until the reasons for it are understood, and it is by no means sufficient to know from observation alone that belts are best for high speeds, that gearing is the best means of forming angles in transmitting power, or that gearing consumes more power, and that belts produce less jar and noise; the principles which lie at the bottom must be reached before it can be assumed that the matter is fairly understood.
Saturday, 23/08/2014
Lorem ipsum dolor sit amet, consectetuer adipiscing elit,
sed diam nonummy nibh euismod tincidunt ut laoreet dolore
magna aliquam erat volutpat ....
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