A desirable feature in band log-mills is the saw deflector, by which, when the direction of the carriage is reversed, the saw blade is automatically drawn back from the surface of the cut, to prevent marking the log, and set back into line before and during the cut. Some band log-mills are made with the engine and the lower band-wheel on a common shaft, and the engine is so arranged that the sawyer has control thereof without leaving his position for running the mill. It is desirable that the position of the band on the wheels be controlled by the operator without leaving his place or stopping the machine, as the collection of dust on the wheels often causes the blade to leave its path, crowding it over against the guides and causing breakage and stripping of the blade. It is also desirable that the tension may be changed at once while the machine is running.
The band saw being so much more delicate and sensitive than the circular, it is well that its feed works be arranged with a friction device in heavy cuts, in order to vary the rate of feed from zero to full speed without stopping the mill.
The increasing use of the band saw has ledto the production of filing and setting frames, in most of which there is a general resemblance, except in very minor details. There is a hori zontal slab or sole piece, betuang two short vertical standards, upon which are journaled two leather-covered pulleys, having a flange on the lower edge of each. One of these pulley stand arils is fixed, and the other is adjustable lengthwise of the machine, in order to take in bands of various len0 hs, to give the proper tension to each while being tiled. There are two vises
on the same side of the machine, one for filing and the other for setting. The filing vise is of extra length, and has jaws closed by three handles. The setting vise is of cast-iron with beveled steel jaws, and has a small gauge at each end, which can be adjusted for different widths of saws.
Saws.—A jig saw, shown in Fig. 14, and recently made by P. Pryibil, has a lever for depressing its upper slide, which conduces much to speed and convenience in placing and removing the saw. The saw runs in adjustable guides, which can be varied in height accord ing to the thickness of the work, and the strain may be adjusted to suit the saw length. The weight of the strain is balanced by a spiral spring. There is an automatic blower to keep the work free from sawdust. The connecting rod has adjustable bearings, which are ar ranged to take up wear endwise in the direction in which it occurs, and not sidewise, as is usual in machines of this class. The machine is started by a friction clutch without belt shifting. Simultaneously with the releasing of the clutch, the machine is stopped by a brake, brought into operation by the same motion which releases the clutch.
In some of the advanced machines for scroll sawing by strained saws, an ingenious feature is that the strain is kept practically constant at all parts of the stroke, by coun teracting the loosening flexibility of the spring by an eccentric roller varying the leverage at each point of the stroke.
Scales : see Balance.