The principal points in a scroll sawing machine are to have the saw held under as nearly equal tension as possible throughout the whole of the stroke; to render the machine readily adjustable for different lengths or sizes of saws, to provide it with means of taking up lost motion, and to avoid vibration when the machine is at work.
Fig. 3122.
Fig. 3123.
A scroll sawing machine constructed by the Egan Company is shown in [Fig. 3122], a sectional view of the saw straining mechanism being shown in [Fig. 3123]. a, a, is a casting having slides for the head b, which is adjustable upon a to suit different lengths of saws, and is secured in its adjusted position by the bolt c and nut d. To the ends of the springs s, a strip or band of leather is secured, the other end passing around the small step f of a roller r, and being secured thereto. The roller r is so supported that it may rise and fall with the strokes of the saw. A second leather band g is secured at t, passes over the large step of r, and at its lower end hooks to the saw, which is strained by the springs s. This reduces the motion of the springs, and thus serves to equalize their pressure throughout the saw stroke.
The lower end of the saw is gripped in a slide or cross-head that is driven by the connecting rod and crank motion shown in the general view [Fig. 3122]. The lever shown at the foot of the machine moves the belt to the fast or loose pulley to start or stop the machine, and operates a brake to stop the machine quickly.