Cylindrical Gears - Gear Nomenclature
Gears with a cylindrical pitch surface are called cylindrical gears.
Spur gears, helical gears, and double helical gears which are used on parallel shafts, and screw gears which are used on non-parallel and non-intersecting shafts are classified as cylindrical gears.
Spur Gears (Cylindrical Gears)