Jig-Saw

Reciprocating saw, of narrow and thin blade, used for interior curvilinear sawing of work which has a continuous margin. Where the inner parts of the design can be reached by a cut from any edge, the band saw is to be preferred. There are two types, the strained and unstrained. The strained are of two kinds: the sash saw, where the saw is stretched acro a frame or sash, and the tension of the blade is given by a screw; and the types where the saw is drawn down by positive connection, and is pulled up by a spring. The spring links can be unhooked from the top of the saw to get it within the edge of the pattern. The reciprocation is universally given in power jig-saws by a crank disk and pitman. A number of forms take pains to secure uniform spring-tension on the saw by systems of leverage. The unstrained saw is simply guided at the upper end.