Fig. 3153.
In this example, however, the table is made in two sections, the front one of which is below the cutter edges to an amount equal to the depth of the cut, and the back one level with the cutter edge, when the latter is at its highest point in its path of revolution, the construction being shown in [Fig. 3153], in which j, j, represents the top part of the main frame of the machine, c the cutter head, b the front or feed table, a the back or delivery table, and w a piece of work being fed in the direction of the arrow.
Upon the upper surface of the frame j, j, and on the feed side of the cutter head is the carriage g, to which are pivoted two links l, l, which support the feed table b. At d is a hand wheel whose screw has journal bearing in a lug from the table, while the screw threads into a nut provided in the carriage. Obviously then by operating the hand wheel d, carriage g is moved along the top of the frame j, and the height of table b is adjusted. Thus if the carriage g is traversed to the left, the link l would fall more nearly to a horizontal position, and table b would lower. Or if g were moved to the right, links l would stand more nearly vertical, and table b would be raised, it being understood that table b is not permitted to move endways. Similarly by means of hand wheel c, carriage h may be moved to adjust the height of table a.
By this construction, the work can bed fairly on the delivery side, as well as on the feeding side of the cutter head, which is not the case when a single table is used.
It is obvious that the work must be fed in opposition to the pressure of the cut, which endeavors to push the work back from the cutter, and this limits the size of work that the machine can operate upon.
Fig. 3154.
The work can be fed easier however, with a cutter skewed or set out of line with the axis of the cutter head. Thus in [Fig. 3154], is the common form of cutter head, carrying two knives placed diametrally opposite, so that the weight of one counterbalances that of the other, and the head will therefore run steadily and smoothly. The knives k, k′ are here set parallel with the axis of the cutter head, hence the whole length of the cutting edge meets the work at the same instant, and a certain amount of time must pass after one cutting edge has left the work before the other cutter edge meets it.