Technical Articles

Helical Gear Note

Posted: 2013-12-05 11:47:57  Hits: 1801
These offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle. Since the gear is curved, this angling causes the tooth shape to be a segment of a helix. The angled teeth engage more gradually than do spur gear teeth, causing them to run more smoothly and with vibration, making then quieter than spur gears. Add to this, the fact that at any time, the load on helical gears is distributed over several teeth, resulting in reduced wear.

  However, due to their angular cut, teeth meshing results in thrust loads along the gear shaft. This action requires thrust bearings to absorb the thrust load and maintain gear alignment.

  Helical gears can be meshed in a parallel or crossed orientations. The former refers to when the shafts are parallel to each other; this is the most common orientation. With parallel helical gears, the teeth of the meshing gears are cut at opposite angles.

  In operation, each pair of teeth first make contact at a single point at one side of the gear wheel; a moving curve of contact then grows gradually across the tooth face to a maximum then recedes until the teeth break contact at a single point on the opposite side.

  In the crossed orientation, the shafts are non-parallel, and teeth of the meshing gears are cut at the same angle. In this configuration they are sometimes known as "skew gears".

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