A wheel that is provided with teeth to mesh, engage, or gear with similar teeth upon another wheel, so that the motion of one may be imparted to the other, is called, in general terms, a gear-wheel.
Fig. 1.
When the teeth are arranged to be parallel to the wheel-axis, as in [Fig. 1], the wheel is termed a spur-wheel. In the figure, a represents the axial line or axis of the wheel or of its shaft, to which the teeth are parallel while spaced equidistant around the rim, or face, as it is termed, of the wheel.
Fig. 2.
