What is a gear with a pressure angle of 20 degrees?
The pressure angle (α) is the angle between the radius line and the tangent line to the tooth profile at a point on the tooth surface (usually the pitch point). (JIS definition)
In recent years, the most common pressure angle for gears has been 20 degrees. On the other hand, gears with diametral pitch (DP), which are mainly used in the United States, also use a pressure angle of 14.5 degrees.
Gears with a pressure angle of 20 degrees cannot properly mesh with gears with different pressure angles, such as 14.5 degrees.
As the pressure angle increases (e.g., 20 degrees compared to 14.5 degrees), the contact ratio becomes lower, while the teeth are less likely to break due to the thicker and stronger tooth root.
Pressure Angle