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Thursday, 24 December 2015

TYPES OF BEVEL GEARS

We have discussed the gear terminology and also the various types of gears in our previous post. Today we will discuss one very important type of gear used in industries i.e. Bevel gear in this post, where we will see the basics of bevel gears and also we will find out the various types of bevel gears here.

Bevel gears are generally preferred in order to transfer the power between two intersecting shafts acting at any angles, however there is one type of bevel gear i.e. hypoid bevel gear which is used to transmit the power between two non-intersecting shafts.

There are lots of industrial applications where we will have to change the direction of rotation of shaft and we will prefer to use the bevel gears in those applications. Two intersecting shafts or non parallel shafts those are co-planar could be assembled with bevel gears to transmit the power from driving shaft to driven shaft.

In lots of industrial applications of bevel gearing mechanism, it has been observed that mechanism of bevel gearing are generally used in order to transfer the power and motion in between two shafts those are intersecting and perpendicular i.e. at 90 degree with each other as we have displayed in below figure to express straight bevel gear where two shaft are connecting each other at right angle, but as we have discussed recently operating angle might be any angle.

Classifications of bevel gears

Depending on the geometry of bevel gears, such gears are divided in various types as displayed here.

Straight bevel gears

Straight bevel gears are the most common type of bevel gear, where teeth will be straight like teeth in case of spur gear but teeth will be taper from larger diameter of tooth  to the smaller diameter of tooth in case of straight bevel gear.

Shaping and coniflex, these are two cutting methods, those are used to cut the straight bevel gear teeth to prepare the straight bevel gear. 100 % straight teeth in straight bevel gears are not acceptable in many applications as they will not permit any misalignment during assembly with gearbox. Therefore there will be slightly curvature in teeth of straight bevel gear and that is termed as crowning.

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Spiral bevel gear

As we are well aware about straight bevel gear, where there is one issue similar to spur gear i.e. engagement of teeth of mating gears will not be gradual and hence there will be noisy operation of straight bevel gear application. Now solution of this problem will be to cut and prepare the curved teeth for bevel gear so that the engagement of teeth of mating gear will be gradual and higher tooth to tooth contact as compared to straight bevel gearing. Spiral bevel gear will provide the silent operation as compared to straight bevel gearing.


Spiral bevel gears are the best choice to use where applications are associated with high rpm and high torque. Spiral bevel gears are normally preferred to use to transmit the power and motion between driving and driven shafts those are typically at ninety degree orientation with each other.

As we have seen helix angle in helical gear, so there will also be one angle called as spiral angle in spiral bevel gear which is expressed as angle between an element of the pitch cone and the tooth trace. Sometimes spiral angle of bevel gear is also called as mean spiral angle.

Zero bevel gears

Zero bevel gears are also a type of spiral bevel gear but the spiral angle of teeth in case of zero bevel gears will be zero. In case of zero bevel gears, the tooth curvature radius will be quite large and hence, as displayed in following figure, zero bevel gear teeth are very similar with teeth of straight bevel gear.

Let us consider the below figure, taken from arrow gear, showing the difference between the spiral angle of zero bevel gear and spiral angle of spiral bevel gear.

Hypoid bevel gears

Hypoid bevel gears are identical to spiral bevel gears but the center lines of both shaft will not intersect to each other but as we have discussed in case of spiral bevel gears center lines of both shaft were intersecting to each other. Application of hypoid bevel gears could be seen in differentials of automobiles.
Image courtesy: Google

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Let us go to our next post “Worm and worm gear

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