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chapter ii
It has been previously stated that the foremost advantages attending the employment of the milling machine are, the production of a great variety of work, and the exact duplication of pieces at an economical cost. In order that these advantages may fully materialize, it is necessary that many requirements be fulfilled in the design and construction of the machine.
These requirements vary to a certain extent with the style and size of the machine; taken as a whole, however, they are materially the same. The machines must all be accurate, economical to operate, and durable. Hence, these may be said to constitute the general requirements of a milling machine. Those qualities upon which accuracy is chiefly dependent are thorough workmanship, especially in aligning the working parts, and sufficient rigidity. In order to be economical in operation, a milling machine must have ample ranges of spindle speeds and table feeds, and plenty of power, so as to adapt it to the many varieties of work. Further, its efficiency must be high, and its parts must be conveniently arranged to allow quick manipulation and ready adjustment. The third general requirement, durability, is, to a great extent, dependent upon the design and quality of materials that enter into the construction of a machine. It is also influenced by several of the already-mentioned points that are essential to accuracy and economy. To particularlize then, the requirements of a milling machine are thorough workmanship, correct alignment of all working parts, sufficient rigidity, wide ranges of speeds and feeds, ample power, high efficiency, durability, and convenience in design and operation.
Workmanship. It is stated above that the dependence of accuracy upon workmanship in the building of a milling machine is of greatest importance in connectoin with the alignments of the different working parts. Correct alignments are most essential because they establish exact positions of the various parts with relation to one another. Any error in alignments is transmitted from one part to another utnil it is finally communicated to the piece of work, where it is liable to be
