The modulus code "M" is an important parameter for calculating each part of metric involute gear, and it is the quotient obtained by dividing the diameter of gear indexing circle by the number of teeth, which is called modulus, and the unit is millimeter. It can express the size of tooth type. When you say spacing, you should call it "Zhou Jie", which means multiplying the modulus by the pie. The depth is called "tooth full height" and multiplied by the modulus of 2.25. Modulus has dozens of standard parameters, and commonly used international standards range from 0. 1 to 50. There is also an English gear, and the parameter is DP. Gear hobbing machine can process a variety of gears with different specifications, which is controlled by the workers who operate the machine tool.