Fig. 1522.
[Fig. 1522] represents a simple form of shaper or planer chuck, such chucks being used upon small planing machines as well as upon shaping machines.
The base a is bolted to the work table, and is in one piece with the fixed jaw b. The movable jaw c is set up to meet the work by hand, and being free to move upon a may be used for either taper or parallel work. To fasten c upon the work, three screws threaded through f abut against the end of c; f being secured to the upper surface of a by a key or slip, which fits into a groove in f, and projects down into such of the grooves in the upper surface of a as may best suit the width of work to be held in the vice; c is held down by the bolts and nuts at g.
The operation of securing work in such a chuck is as follows:—The screws both at f and at g being loosened, and jaw c moved up to meet the work and hold it against the fixed jaw b, then nuts g should be set up lightly so that the sliding jaw will be set up under a slight pressure, screws f may then be set up and finally nuts g tightened.
Fig. 1523.
This is necessary for the following reasons:—The work must, in most cases, project above the level of the jaws so that the tool may travel clear across it; hence, the strain due to holding the work is above the level of the three screws, and the tendency, therefore, is to turn the jaw c upwards, and this tendency the screws g resist. A similar chuck mounted upon a circular base so that it may be swivelled without moving the base on the work table is shown in [Fig. 1523]. The capacity to swivel the upper part of the chuck without requiring the base of the chuck to be moved upon the table is a great convenience in many cases.
