The main methods for processing threads on vertical CNC lathes include the following:

1. Single-point thread processing: This is one of the most common thread processing methods on vertical CNC lathes. By using a single-point tool, threads are formed by cutting point by point on the workpiece. This usually requires a CNC program to control the tool's path and feed rate.

2. Thread milling: Vertical CNC lathes use thread milling cutters for thread processing. The shape of the thread milling cutter allows it to cut the contour of the thread on the surface of the workpiece. This is usually suitable for machining large diameter or long threads.

3. Thread turning: Use CNC lathe for thread turning. In this method, the feed motion of the turning tool and the rotational motion of the spindle are precisely controlled in order to form the required thread.

4. Overall feed thread processing: Utilize the overall feed function of the CNC lathe to realize thread processing by simultaneously controlling the movement of the spindle and feed axis. This can improve processing efficiency.

5. Thread grinding: Vertical CNC lathes can use thread grinders to grind threads that require high precision and high surface quality. This requires precise control and adjustment, often in very demanding applications.

In all these methods, the writing of CNC programs and the selection of cutting tools are key steps. The program needs to accurately define parameters such as tool path, feed rate, spindle speed, etc. to ensure the accuracy and quality of thread processing. In addition, the selection of tools should also take into account factors such as thread specifications and workpiece materials.