When the upper wheel receives the strain of the saw, then the continued revolution of shaft s will cause the nut n to lift endways in its bearing e, the screw m acting as a fulcrum to cause the lever l to compress the rubber cushion p. The amount of tension on the saw is tested by springing it sideways with the hands. Now suppose the saw to be properly strained, and that a piece or chip of wood accidentally gets between the saw and the lower wheel, and the result will be that the slide c will (from the extra strain caused by the chip) move down on its slideway b, which it is capable of doing, because the long arm of the lever l can move down, compressing p, and this will prevent the saw from breaking.
To cant the wheel for leading the saw true to the lower wheel, the following means are provided:
The upper wheel bearing rests on the fulcrum at a, and is guided sideways by the screws c and d. At f is a stud threaded into the bottom half of the upper wheel bearing, the wheels g and h threading upon f. The weight of the upper saw wheel endeavors to lift the end j of the wheel bearing, and wheel h determines how much it shall do so, while wheel g acts as a check nut to lock the adjustment.
Fig. 3136. Fig. 3137.
The feed rolls are carried in slides which are operated in slideways by means of screws, and the two back rolls, or those nearest to the column are maintained vertical. The two front ones, however, are provided with means by which they may adjust themselves to bear along the full depth of the work, notwithstanding that it may be taper. The construction by means of which this is accomplished is shown in [Figs. 3136] and [3137], in which a is front and b a back feed roll. The bearings of feed roll a abut against rubber cushions c, c, whose amount of compression is regulated by the set screws d, d.
Fig. 3138.