This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 Excerpt: ...break-lathes, which have broad beds, and lathes with sliding beds, etc. With these exceptions, the convenience of having the screw outside, where it can be easily seeu and got at for cleaning, and the simplification of the clasp-nut arrangement, far outweigh merely theoretical considerations. A similar objection might ...
Read More
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 Excerpt: ...break-lathes, which have broad beds, and lathes with sliding beds, etc. With these exceptions, the convenience of having the screw outside, where it can be easily seeu and got at for cleaning, and the simplification of the clasp-nut arrangement, far outweigh merely theoretical considerations. A similar objection might be urged against the rack and pinion for sliding. It is closer to the bed than the screw; but it is not as near as it should be to the resisting force. But, everything considered, it is in the best possible position. The American rack is placed the same as the English--under the front ways. In the largest lathes the weight of the screw, which is sometimes as much as 4 inches or 41 inches in diameter, has to be supported by intermediate bearings at intervals. These bearings are either of the tumbler kind (see Fig. 134, p. 69), or else they are fixed, as in Fig. 232, p. 129, in which case the clasp-nut can only fit over the screw through a portion of its circumference. Provision is made against end-play by means of hardened steel washers and check-nuts. Clasp-nuts are fixed, the screw revolving. There is one exception to this in the practice of Hulse & Co., of Manchester. The rotation of heavy screws being considered objectionable, these are fixed in the largest lathes, and the nuts revolve. A separate shaft, deriving its motion from the change-wheels, transmits movement through gearing to the rotating nuts. The direction of rotation for up and down movement of the rests is regulated by means of a clutch at command of the lathe-man. Clasp-nuts are of the double, or the single forms, the first embracing the screw all round, the latter through the half, or a lesser portion of the circle. Fig. 145 illustrates the first in front-view, the nut an...
Read Less
