Gear Wheels, Toothed wheels

The usual forms are spur-wheels, where the shafts are parallel; bevel-wheels, where the shafts intersect; skew-bevel, where the shafts are not parallel and do not intersect; and screw-gearing, where one of the wheels is a screw. A rack is a wheel with an infinite radius, so that the pitch surface is a plane. A pinion is a smaller wheel of a pair or train. A shrouded pinion is one in which the teeth are strengthened by being covered in at the ends up to the pitch line. Miter gears are bevel wheels where the two cones are equal, and the shafts at right angles. Helical gear are wheels where the teeth elements are parts of screws. Each tooth is either on one helix as an axis, or else one right and one left helix meet in the middle of the face. This latter form gives IMG:content-0243.jpg:[merged small][merged small][graphic][subsumed][merged small]