The gear hobbing machine is for preliminary machining of the tooth shape, and the shaving and grinding are for finishing. However, some gears cannot be processed by the hobbing machine and a gear shaping machine is required. The chamfering machine deburrs and chamfers the tooth profile, which is relatively simple.
Tools are very important for gear processing and are relatively expensive. Many of them require special tools. If you want to open a factory, this is a huge cost.