The tooth surface hardness, it is divided into gentle tooth surface equipment transmission and challenging tooth surface area equipment transmission. When the tooth floor hardness of the two wheels (or 1 of them) is much less than or equivalent to 350HBW, it is known as gentle tooth surface transmission when the tooth surface hardness of the two wheels is >350HBW, it is called tough tooth surface area transmission. Delicate-tooth area gear transmission is often utilized for general minimal-speed gear transmission that does not require large precision, and tough-toothed surface equipment transmission is often employed for gear transmission that needs robust bearing potential and compact framework.