The worm gear is used for the rotation between two cross shafts (the cross angle is generally right angle). Generally, the worm is driven and the worm gear is driven. It is used for deceleration to obtain a large transmission ratio.
In worm gear transmission, the most commonly used worm is cylindrical Archimedes worm. The axial tooth profile of this worm is a straight line, and the axial section is isosceles trapezoid, which is similar to trapezoidal thread. The number of teeth of the worm is called the number of heads, which is equivalent to the number of threads of the thread. It is usually single head or double head.
The worm is equivalent to a helical cylindrical gear, and its teeth are distributed on the annular surface, so that the gear can wrap the worm to improve the contact condition, which is a feature of the worm gear shape.
