[L1] 1 Tooth Profile [L2] 1) Definition of Tooth Profile [L4] - The curve of the gear tooth contact part. [L4] - Since gear teeth move in sliding contact, the tooth profile corresponds to the locus points of the common normal at the contact point of two meshed teeth. [L4] - If the common normal is not a curve, smooth meshing cannot be achieved. [L4] - Involute tooth profiles and Cycloid tooth profiles are used for tooth curves. [L2] 2) Pressure Angle [L4] - The angle formed by the normal line of the gear tooth surface and the line orthogonal to the Pitch Circle Diameter (PCD). Called Pitch Point Pressure Angle. [L4] - In an involute gear, it is the angle formed by the line passing through the pitch point on the line of action and tangent commonly to the pitch circles of two gears. It refers to the angle formed by the radial line at a point on the gear tooth surface and the tangent at the pitch circle. [L4] - Pitch Point Pressure Angle refers to the angle between the line of action passing through the pitch point and the tangent of the pitch circle at the pitch point. The standard involute tooth pressure angle is 20°. [L4] - The angle formed by the common tangent of the pitch circles of two gears and their line of action. [c] [L1] 2 Involute Tooth Profile [L2] 1) Definition [L4] - The trajectory drawn by a point on a string when the string is unwound while being pulled taut from a base circle. [L2] 2) Features [L4] - Easy to manufacture. Gear machining is easy and does not require special machining methods. Low work difficulty. [L4] - High-precision gear machining is possible. [L4] - Good interchangeability (compatibility). [L4] - Even if there is an error in the center distance of a pair of gears, the effect on meshing is small. [L4] - Tooth interference may occur, causing undercut. [L4] - Profile shifted gears can be made (Can increase gear durability, but machining difficulty is relatively high). [L2] 3) Involute Image [c] [L1] 3 Cycloid Tooth Profile [L2] 1) Definition [L4] - A type of gear tooth profile where the epicycloid drawn on the pitch circle is the addendum (tooth tip), and the hypocycloid drawn inside is the dedendum (tooth root). [L4] - The trajectory drawn by a point on a rolling circle when it rolls without slipping on the outside/inside of the pitch circle circumference. [L4] - Usage is limited to small gears for precision machinery or measuring instruments. [L2] 2) Features [L4] - Thrust and bending strength are small. [L4] - Sliding rate is uniform (Uniform wear, noise reduction). [L4] - Profile shift cutting is impossible and unnecessary (Undercut does not occur, so profile shift cutting is unnecessary). [L4] - High precision. [L4] - Manufacturable machining methods are limited. [L2] 3) Cycloid Image [c]