Classification by pitch line of tooth surface:
a. Arc tooth: its teeth are cut with a circular end milling cutter. Circular arc tooth is a part of circular arc, which is the pitch line of the imaginary plane gear. The tooth line of the workpiece is conjugate with the imaginary plane gear.
b. Extended epicycloid bevel gear: the pitch line of the tooth surface of the gear is a part of the extended epicycloid.
c. Quasi involute bevel gear: the gear is machined on a gear milling machine with a conical hob. The assumed pitch line of plane gear is quasi involute. The cutting process is continuous.
Classification by axis mutual position:
a. Vertical intersection of two axes: the intersection angle of two axes is 90 °. In general, spiral bevel gears use vertical intersecting axes. When the bevel gears intersect the axis, there is no relative sliding on the tooth rectangle.
b. Bevel gears with intersecting but not perpendicular axes:
c. Bevel gear with axis offset: this kind of gear is equivalent to offsetting the axis of the pinion which is perpendicular to the intersecting axis up or down by a distance, which is called “offset”. The axis offset can make the pinion have a larger helix angle, generally up to about 50 °. As the helix angle increases, the end modulus of the small wheel is also increased, so the diameter of the small wheel is also increased, and the strength and service life of the small wheel are increased. This kind of gear has relative sliding along the direction of tooth length and tooth height. The axial offset gear is commonly called “hyperbolic gear”, because the pitch surface of this gear is a part of the surface of hyperbolic revolution body, on which there is relative sliding motion. There are also called “hypoid gear” or “hypoid gear”.
Classification by tooth height:
a. Constant height bevel gear: the tooth height is the same from the big end to the small end of the tooth. The face angle, root angle and pitch angle of this kind of gear are equal. Oerlikon bevel gear milling machine with continuous cutting method is generally used to process equal height teeth. Arc tooth bevel gear can also be used with equal height teeth.
b. Tapered bevel gear: the height of the tooth from the big end to the small end is gradually reduced. Some of them are reduced in proportion to the length of the pitch cone generatrix; some of them are parallel to the tooth root of the matching gear, and the vertex of the face cone no longer intersects with the pitch cone vertex. This kind of gear can ensure that there is an equal gap of the tooth top along the tooth length direction. Most of the bevel gears with circular arc teeth are involute.
d. Double shrink tooth: the apex of root cone and face cone of this kind of gear do not coincide with the apex of pitch cone. The apex of the root cone is located outside the apex of the pitch cone, and the angle of the root cone is smaller than that of the non double contraction tooth.