Thread & worm whirling machines is a term used in the field of mechanical engineering technology. It is believed to be a type of machine tool used for making threads and worm shapes. Threads are often needed in the production of screw connections, while worm molds are used to create drive systems for machine tool drive or switching systems, for example. However, it is difficult to say without more information which specific machines are meant. For example, it could be threading lathes or worm milling machines.