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The gear reduction ratio of the worm gear is generally 20:1, sometimes even up to 300:1 or greater.

Many worm gears have an interesting feature that other gear sets do not possess: the worm can easily rotate the gear, but the gear cannot rotate the worm. This is because the protrusions on the screw are shallow, and when the gear tries to rotate the screw, the friction between the gear and the screw will keep the screw in place. The copper worm gear of the gate gate is an application example