The conventional "scroll saw" known to woodworkers has a parallelogram motion. If you think about it, and visualize the blade motion from the side, this means that the blade is not only moving up-and-down on each stroke, but also in-and-out as the arms of the parallelogram move in arcs. This is fine for woodworking, where there's a certain amount of give in the work. For metalworking, though, such a parallelogram motion is a design for breaking blades - especially if using jeweler's saw blades for fine work.
A proper jigsaw has a blade which moves straight up-and-down. This may be accomplished by using a Scotch Yoke mechanism in a base below the blade and a spring return mechanism above it. Once you use such a saw, you'll never willingly go back to a parallelogram-motion saw again.
Craftsman (Emerson) 103.0403/103.0404
A splendid saw with an artistic edge.
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