Gears are made from a wide variety of materials with many different properties. Hypoid bevel gears is a type of having teeth on a circular face that are worm –like drive on non-intersecting axes. Hypoid bevel gears can be mounted on a hub or shaft. A hub is a cylindrical projection on one or both sides of gear, often for the provision of a screw or other shaft attachment mechanism. Hubless gears are typically attached via press fit, adhesive, or internal keyway. Shaft mounting choices include keyway, set screws, hub claming screws, split, and simple bore.
Hypoid bevel gears are operating more quietly, stronger and can be used for higher reduction ratios. They also have sliding action along the teeth, potentially reducing efficiency. Hypoid gearings are used in power transmission products.
Hypoid bevel gears are similar to spiral bevel except that the pitch surfaces are hyperboloids in shape rather than conical and the gears can be anti backlash which means that they have an assist, typically one or more springs, which eliminate backlash in the gear mesh. In hypoid gear design, ring gears and the pinion are always of opposite direction. The hypoid bevel gears can be designed with fewer teeth. Hypoid gears can be considered as halfway between a spiral bevel gear and a worm gear.
Hypoid bevel gears may be used for both speed-reducing and speed-increasing drives. In speed-increasing drives, however the ratio should be kept as low as possible and the pinion mounted on anti-friction bearings; otherwise bearing friction will cause the drive to lock.
Hypoid bevel gears are recommended for industrial applications where maximum smoothness of operation is desired; secondly, for high reduction ratios where smoothness of operation, compactness of design, and maximum pinion strength are important; thirdly, for non-intersecting shafts.
One more specifications to be consider while choosing the gears include pitch diameter, bore diameter, face diameter, and pitch diameter. The number of teeth diameter will dictate pitch of gear. The face width is width of the teeth. The bore diameter is center bore for gears with a bore. Hypoid bevel gears have the tooth axis is parallel to axis of rotation. Pressure angle is the angle between the line of force or action and the tangent to the pitch circle at the point of mesh.