Fig. 1513.
When the work is very narrow, however, the use of a parallel piece to regulate its height is dispensed with, and the top surface b of the jaw, in [Fig. 1513], is used to set the work by. A line is marked on the work surface to set it by and a surface gauge is set upon the face b, its needle point being set to the line in a manner similar to that already explained with reference to chucking work in the lathe.
All work should be so set that the tool will traverse across the longest length of the work, as denoted by the tool in [Fig. 1502], and the arrow marking its direction of traverse.
The general principles governing the use of the shaper vice having been explained, we may now select some examples in its use.
Fig. 1514.
[Fig. 1514] represents a simple rectangular piece, and in order to have the tool marks run lengthwise of each surface (which is, as already stated the most expeditious) they must be in the direction of the respective arrows. In a piece of such relative proportions there would be little choice as to the order in which the surfaces should be shaped, but whatever surface be operated on first, that at a right angle to it should be shaped second; thus, if a be first, either b or d should be second, for the following reasons.
All the surfaces have sufficient area to enable them to serve as guides in setting the work, hence the object is to utilize them as much as possible for that purpose. Now, suppose that surface a has been trued first, and if c be the next one, then the bedding of surface a upon the vice surface or the parallel pieces must be depended upon to set a true while truing c. Now the surfaces b and d may both, or at least one of them, may be untrue enough to cause the work to tilt or cant over, so that a will not bed fair, and c will then not be made parallel to a. It will be preferable then to shape a first and at the second chucking to set a against the stationary jaw of the vice, so that it may be held true.