Thread-processing tools are manual or machine-operated implements used to create or repair threads; this is primarily achieved through two types of processes: cutting and plastic deformation (rolling) . The cutting process utilizes shaped tools to remove material and form the thread profile, whereas the plastic deformation process employs dies to induce plastic flow within the workpiece material, thereby forming the thread.
Based on their underlying process principles, thread-processing tools are broadly categorized into cutting tools and plastic deformation (rolling) tools. Cutting tools include taps (used for internal threads), dies (used for external threads), thread turning tools, thread milling cutters, and self-opening thread cutting heads, among others. Plastic deformation tools include thread rolling dies (flat dies), thread rolling wheels (radial, tangential, and rolling heads), and self-opening thread rolling heads. For workpieces made of softer materials, fluteless forming taps can also be used to process internal threads via cold extrusion (with a maximum diameter reaching approximately 30 mm).
As the primary cutting tool for processing internal threads, the tap is classified in various ways. Based on their geometry, taps can be categorized into spiral flute taps, spiral point taps (gun taps), straight flute taps, and pipe taps. Based on their application environment, they are classified as hand taps or machine taps. Tap classifications also distinguish between cutting taps and forming taps. Furthermore, based on their specifications, they are categorized into metric, American, and British standard taps.
Thread rolling tools are primarily classified into two categories-thread rolling dies (flat dies) and thread rolling wheels-depending on the specific type of die employed. The flat-die rolling process involves two flat dies, each featuring a thread profile, which move relative to one another in a staggered motion to process the workpiece. Thread rolling using wheels is further subdivided into three forms: radial rolling, tangential rolling (planetary rolling), and rolling head processing; among these, rolling head processing is frequently utilized on automatic lathes to produce short threads.
