The worm gear (Fig. 34) is a special case of screw and nut, where the latter is replaced by a toothed wheel called a worm wheel.
The worm is two-threaded, and the worm wheel g has 200 teeth.
The teeth work in with the thread of the screw or worm, and thus, as the worm revolves, the worm wheel revolves about its axis.
A worm wheel and two eccentrics are machined up out of one piece and serve to operate the plungers.
If the polar axis is set vertical and the worm wheel unclamped, the instrument is transformed into an alt-azimuth mounting.
The shaft of worm wheel g is omitted in Fig. 3149, so as to leave the belt-shifting mechanism for pulleys q, q′ exposed to view.
By means of the handle h and the worm and worm wheel at w, the shaft s is revolved.
The second worm wheel has 196 teeth, and its edge is divided into 49 divisions.
A short length of screw used to drive a worm wheel, and sometimes termed an endless screw.
To discharge the dough, the trough was tilted by means of a worm and worm wheel, the latter being secured to the trough.