The problem of interference in an involute pinion, which has to come in external mesh with a gear, can be avoided by

Question

Question

This question was previously asked in

BPSC AE Paper 6 (Mechanical) 2019 Official Paper

increasing the pressure angle
positive profile correction on pinion and corresponding negative profile correction on gear
machining the pinion teeth through hobbing so that the interfering portion gets undercut
all of the above

Answer 1

Concept:

When two gears are in mesh at one instant there is a chance to mate involute portion with the non-involute portion of the mating gear.
This phenomenon is known as the INTERFERENCE and occurs when the number of teeth on the smaller of the two meshing gears is less than a required minimum.
The phenomenon when the tip of the tooth undercuts the root on its mating gear is known as interference.
Methods of elimination of Gear tooth Interference:
- Use of a larger pressure angle (having a larger pressure angle results in a smaller base circle. As a result, more of the tooth profiles become involute)
- Under-cutting of a tooth (A portion of teeth below the base circle is cut off. When teeth are produced by this process, the tip of one tooth of gear will not contact the non-involute portion of the tooth of other gear)
- Tooth stubbing (In this process a portion of the tip of the teeth is removed, thus preventing that portion of the tip of the tooth from contacting the non-involute portion of the other meshing tooth).
- Increasing the number of teeth on the gear can also eliminate the chances of interference.
- Increasing slightly the center distance between the meshing gears would also eliminate interference.
- Tooth profile modification or profile shifting (Using profile shifted gears (gears with non-standard profile) can also be an option to eliminate interference. In profile shifted meshing gears, the addendum on the pinion is shorter compared with standard gears).