What is involute?

　　An involute, as the name implies, is the curve that the point above it leaves a fixed point(the center of the base circle).

　　If you wrap a line around the cylinder, fix the end of the line to a pen, and let the tip of pen hold the line, gradually remove the cylinder and draw a trace, then the trace is an involute.

　　Involute cylindrical gear is one of the gears. When the tooth form consists of the involute line and transition line, it is called an involute gear. Because it has many advantages, so the application is very wide.

　　There are two commonly used methods to process involute tooth form, namely forming methods and generating methods.

　　1. Gear Milling

　　Use a disc-shaped modular milling cutter or a finger milling cutter to mill teeth belongs to the forming method. The profile of milling cutter teeth corresponds to the profile of gear teeth. In terms of machining efficiency and precision, this is method is relatively low, which is only suitable for small batch production.

　　2. Form Grinding

　　It belongs to the forming method. Because the grinding wheel is not easy to be dressed, it seldom uses.

　　3. Gear Hobbing

　　It belongs to the generative methods, whose working principle is equivalent to the meshing of a pair of the helical gear. The prototype of gear hob is a helical gear with a large helix angle. Because the number of teeth is small(usually, z=1), the teeth are very long, which form a worm with a small helix angle around the shaft. After grooving and shoveling, it becomes a hob with cutting edge and back angle.

　　4. Gear Shaving

　　In mass production, gear shaving is a commonly used method for non-hardened tooth surfaces. Its working principle is to use shaving cutter and processed gear to make free meshing movement, with the help of the relative slippage between the two, very fine chips are shaved from the tooth surface, which can improve the precision of tooth surface. Shaving can also form a drum tooth to improve the position of the contact area of the tooth surface.

　　5. Gear Shaping

　　Except for gear hobbing, as a generating method, the gear shaping is a commonly used tooth cutting technology. In the process of gear shaping, the circular motion of gear shaper cutter and the workpiece is the feed motion of gear shaping.

　　6. Generating Method Grinding

　　The cutting motion of generating grinding is similar to the hobbing, which is a tooth form machining method. For the hardened gear, it is the only method. It can use a worm wheel to grind the teeth, the tapered wheel or the disc wheel can also.