Machine shop tools and shop practice : a book of practical instruction describing in every detail the construction, operation and manipulation of both hand and machine tools ... by Van Dervoort William Humphrey 1869-

Author:Van Dervoort, William Humphrey, 1869-
Language: eng
Format: epub, pdf
Tags: Machine-tools
Publisher: New York : N. W. Henley

MODERN MACHINE SHOP TOOLS.

The length of this slot is determined by the amount of casing rotation required. In action, the table starts on its stroke; B and G rotate until I strikes the end of the slot H and the rack has been moved up or down, depending upon which side of the center the pin G is. As the table continues its stroke, the disc A slips between the washers E and F, and G remains stationary. When the table starts on its return stroke, A rotates in the opposite direction, carrying with it B and G until the pin strikes the other end of the slot, the rack having received motion in the opposite direction to that given on the forward stroke. Thus the rack is moved up and down once each time the table moves forward and back, and the amount of the rack motion depends upon the distance B is from the center and is independent of the length

of the table stroke. A pinion X gears with the rack and through a shaft carries the gear A, Fig. 393. Gear B rotates free on the shaft, gears with C, and on its face carries the double pawl D. If the lower foot of this pawl, as it stands in the cut, is thrown in, it slips on the up stroke of the rack, but-drives the gear B in the direction of the arrow on the down stroke. If the upper foot is thrown in it slips on the down stroke and carries gear B

in the opposite direction, the direction of feed being reversed. It is evident that with the wrist pin G, Fig. 392, on the same side of the center, the feed occurs at the beginning of the forward stroke when the feed is in one direction, and reversal of the feed makes it occur at the beginning of the return stroke. The wear on the feed mechanism is least when the feed occurs at the beginning of the return stroke, as it is not then necessary to move the tool while cutting. On the other hand, feeding on the return stroke makes the wear on the tool in dragging back somewhat greater. When the heads are attached to the face of the housings, they are given a vertical feed on the housing in a manner similar to that already described. By removing the gear C from the cross screw and putting it on the feed rod, the vertical feed is operated in a manner similar to that for the horizontal feed.

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