gears are wheel and axles with teeth. Other simple machines can be
found in the design of apple parers. Paring arms are third or first
class levers; many push-offs are first class levers (right). Blades
are wedges. Some early wooden parers have belt-drive systems that
classified as pulley systems. Clamps are the most obvious use of the
screw. The threaded-shaft that carries the fork in many lathe parers
is a screw.
Oriole and Jersey lathe parers make a more subtle use of the screw. A
large wheel is fitted with a screw thread, which advances through
teeth as the
machine is cranked (left).
Maxam’s Patent Automatic Scroll Wheel Apple Parer may exhibit the most interesting use of the screw. The hub (right) of the hand-driven gear is molded into a screw. The threads of the screw push a first class lever connected to a gear system that rotates the paring arm.
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