Chap. XIII.

TOOLS AND MACHINES.

1039

is moved onwards by the screw, as the cylinder to be cut revolves from the motion con-veyed to it by the action of the lathe; this revolving motion also affects the small screwsin the rest, which yields to the point of the tool on sliding along a spiral action, which isregulated by the proportion given to the diameters of the two cogged wheels ; when thediameter of that on the screw is twice that which acts in the slide, the pitch of the threadwill be double or twice that of the slide screw'.

Cutting the Teeth of Wheels is a similar operation’: the wheel to be cut is fixed on a spindle,which forms a portion of the dividing wheel at the end, by fitting into a socket or chuck, sothat when this wheel is moved round, according to the required divisions made on its face.

Fig. 1594.

CUTTING THB TEETH OP WHEELS,

that to be cut presents its edge at the same time; the slide-rest, furnished with a revolvingcutter, works at right angles against the edge of the wheel on which the teeth are to be cut,and the whole is speedily completed with great exactness. The dividing wheel is held fastas each successive tooth is formed by an iron holder, which is removed to a fresh point everytime the cutter has perfected its work.

Planing Machine, here showm, has a strong vertical iron spindle, carrying the horizontalwheel, in the rim or circumference of which thirty holes are pierced, into which are intro-duced twenty-eight gouges or cutters and two planes ; this perfectly level wheel, being wellbraced by the aid of the machinery at top, revolves ninety times in a minute. The timber

4 ■j

Fig. 1595.

PLANING MACHINE.