Page:Practical Treatise on Milling and Milling Machines.djvu/43

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Erection and Care of Machine

Erection. A machine should be placed upon a level, and, if possible, a solid floor or foundation. If the foundation is not firm, undue vibrations will exist and possibly impair its accuracy and durability. Either stone or concrete makes an excellent foundation for the larger sizes. Neither of these can be used, however, when it is desired to place a machine above the ground floor of a building, and it is best, in this case, to locate it directly over a beam; not in the middle of a bay.

Ordinary wooden shingles are commonly used in leveling a machine. When the exact position has been determined, the fastening screws or bolts should be screwed down until nearly tight. A spirit level should then be used to test the top of the table, both longitudinally and transversely. If the machine is too low at any corner, drive a shingle under the base at this point to bring it up. When the table is found to be level in every direction, the nuts, or bolts, should be brought up solidly. It is well, even after tightening the bolts, to test the surface of the table once more, as this tightening sometimes throws the machine out of level again.

Counter-shaft. Putting up the counter-shaft, when one is employed, is usually the first operation in installing a machine. It is generally placed directly over cone drive machines because of the interference of the driving belt with the upper part of the frame if it is located very far at either side. With constant speed drive machines, it is not necessary to place the counter-shaft directly overhead. It may be placed diagonally as long as the belt does not interfere with the overhanging arm when it is pushed back.

The counter-shaft should be level and accurately aligned paralledl with the main, or driving, shaft. Where the beams are not uniform enough to bring the stringers to which the counter-shaft hangers are attached level, it will be necessary to shim between the feet of the hangers and the stringers to make the shaft level. The holes in the feet of the hangers are usually in the form of slots, which allow the hangers to be slightly adjusted when aligning the counter-shaft with