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ONE:Finishing and fitting relates to giving true and accurate dimensions to the parts of machinery that come in contact with each other and are joined together or move upon each other, and consists in cutting away the surplus material which has to be left in founding and forging because of the heated and expanded condition in which the material is treated in these last processes. In finishing, material is operated upon at its normal temperature, in which condition it can be handled, gauged, or measured, and will retain its shape after it is fitted. Finishing comprehends all operations of cutting and abrading, such as turning, boring, planing and grinding, also the handling of material; it is considered the leading department in shop manipulation, because it is the one where the work constructed is organised and brought together. The fitting shop is also that department to which drawings especially apply, and other preparatory operations are usually made subservient to the fitting processes.As no motion except rotary can be continuous, and as rotary movement of tools is almost exclusively confined to shaping cylindrical pieces, a proper distinction between machine tools which operate in straight lines, and those which operate with circular movement, will be to call them by the names of rotary and reciprocating. ONE:The first principle to be pointed out in regard to belts, to distinguish them from shafts as a means of transmitting power, is that power is communicated by means of tensile instead of torsional strain, the power during transmission being represented in the difference of tension between the driving and the slack side of belts. In the case of shafts, their length, or the distance to which they may be extended in transmitting power, is limited by torsional resistance; and as belts are not liable to this condition, we may conclude that unless there are other difficulties to be contended with, belts are more suitable than shafts for transmitting power throughout long distances. Belts suffer resistance from the air and from friction in the bearings of supporting pulleys, which are necessary in long horizontal belts; with these exceptions they are capable of moving at a very high rate of speed, and transmitting power without appreciable loss.A solid milling cutter must be an accurately finished piece of work, made with more precision than can be expected in the work it is to perform. This accuracy cannot be attained by ordinary processes, because such tools, when tempered, are liable to become distorted in shape, and frequently break. When hardened they must be finished by grinding processes, if intended for any accurate work; in fact, no tools, except gauging implements, involve more expense to prepare, and none are so liable to accident when in use.

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