Why can't the gear turn less than 17 teeth?

Gears with less than 17 teeth will not affect the use, but 17 teeth will be inconvenient to handle under certain conditions.

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The accurate statement is: standard involute spur gear when the number of teeth is less than 17, the root will be cut to reduce the gear strength is not said to be unable to turn.


The so-called undercutting, when cutting the teeth by the Fan method, under certain conditions, the tip of the cutter is cut too much into the root of the tooth, and the involute tooth profile of the root is cut off.


17 teeth are from the processing method, and also depend on the processing method. If the machining method of the gear is changed or improved, such as the forming method and the displacement processing (here, especially the spur gear), there will be no undercut phenomenon. The limit number of 17 teeth.