BAND SAWING MACHINES.
Fig. 3125.
The simplest form of band sawing machine is that in which the work is fed to the saw by hand, a machine of this class, constructed by J. A. Fay & Co., being shown in [Fig. 3125]. It consists of a standard or frame a, carrying the saw-driving wheel b, and the upper wheel c, the saw being strained upon these two wheels. The lower wheel runs in fixed bearings, while the bearing of the upper wheel is carried in a slide provided in the frame, being operated in the slide by a screw, whose hand wheel is shown at e, so that it may be suited for different lengths of saws.
The bearing of the upper wheel is so arranged that the tension placed on the saw may be governed by a weighted lever f, which enables the upper bearing to lower slightly, so that if a chip should fall between the saw and the lower wheel, it may not overstrain, and therefore break the saw.
At j, is a bar carrying a guide g, which sustains the saw against the pressure of the cut, a similar guide being placed below the table t, at g′. This latter guide is fixed in position, whereas the upper one, g, is adjustable for height from the work table, so that it may be set close to the top of the work, let the height of the latter be what it may. g′′ is a guide and shield for the saw at the back of the machine, and h is a shield to prevent accident to the workman, in case the saw should break.
Band saws are ribbons of steel, brazed together at their ends and having their teeth provided on one edge. The widths of band saws vary from 1⁄16 inch to 8 inches, and their thicknesses from gauge 18 to 22 gauge, according to width.
The advantage of the band saw lies in that it may be run at high velocity, may be made thin, and its cutting action is continuous.
As a band saw is weak, it is desirable to have the teeth as short as possible and leave enough room for the sawdust, so that it shall not pack in the teeth.