Movement No. 121 converts alternating rectilinear motion into intermittent rotary motion using a disk-wheel fitted with a click (pawl) that engages a cog-wheel. A rod connected to the disk-wheel drives it back and forth in a reciprocating linear motion. Mounted on the disk-wheel is a pivoting click that engages the teeth of a cog-wheel. On one stroke, the click catches a tooth and advances the cog-wheel by one step; on the return stroke, the click slides over the teeth without engaging, allowing the cog-wheel to remain stationary. The direction of the intermittent rotation can be instantly reversed simply by flipping the click over to engage the opposite side of the teeth. This reliable step-feed mechanism was widely used in planing machines, slotting machines, and other metal-cutting tools to advance the workpiece or tool incrementally with each cutting stroke.
121. Alternating rectilinear motion of the rod attached to the disk-wheel produces an intermittent rotary motion of the cog-wheel by means of the click attached to the disk-wheel. This motion, which is reversible by throwing over the click, is used for the feed of planing machines and other tools.