and miter gears are conical-shaped with teeth cut on their faces
which transmit power and motion between two shafts positioned at typically a
90-degree angle (or less for some bevel gears).
Change gears are flat, hubless spur gears with
straight teeth that mesh on parallel axes to transmit rotary motion.
Helical gears have teeth set at an angle rather
than parallel to the axis of rotation to enable them to transmit motion at
greater speeds and torque.
Internal gears have straight teeth along the
internal diameter rather than pointing outward, which mesh with one or more small
pinions inside the gear, and they transmit rotary motion between parallel
shafts that turn in the same direction.
Rack and pinion gears are made of a small round
spur gear (the pinion) and a flat bar with evenly spaced teeth (the rack).
gears are simple cylindrical or disk-shaped gears with straight teeth
that interconnect on parallel axes to provide uniform rotary motion.
Worm gears, also called worm drives, use a long,
threaded cylinder called a worm that meshes with the teeth of a worm wheel
(similar to a spur gear) to transmit motion.