Spur gears are the “traditional” gear shape, with a cylindrical form surrounded by external teeth, but they certainly aren’t the only type of gear available. One of the next most common gear forms is the helical gear, is also cylindrical gear but with teeth that wrap around the gear in a helix. Helical gears compensate for many of spur gears’ disadvantages. Spur gears tend to take more damage over time, especially when exacerbated by improper fits or applications, and produce excessive noise when bearing high loads or running at high speeds.
So what is it about helical gears that makes them so special? For starters, their teeth are elongated, running at an angle to the gear’s axis, but you may not realize these four interesting things about helical gears:
- Helical teeth can run crossed to each other. Your intuition would tell you the angled teeth of helical gears would need to run parallel with each other, but they can also become crossed. When used this way, they’re frequently called skew gears.
- Helical produce end thrust. Though helical gears have many advantages over spur gears, they also have a few disadvantages. For example, they bear excessive thrust along the axis of the gear that needs to be compensated for with thrust bearings, or extra friction between teeth.
- Helical gears are quieter. Because tooth contact in helical gears is more of a sliding action vs the slapping action of spur gears, they tend to be much quieter than spur gears (and perfect for some low-noise applications).
- Double helical gears present new challenges. Double helical gears, as you might imagine, look like two helical gears stacked on top of one another, with teeth slanted in opposing angles. Double helical gears don’t have a thrust problem, but are more difficult to manufacture.
Helical gear manufacturing is more complicated than spur gear manufacturing, and requires more attention to detail. If you’re interested in producing helical gears for your next project, contact Federal Gear today!