What Is a Threading Tool?
A threading tool is a specialized cutting instrument used in a lathe to create threads on a workpiece. These threads can be external, such as those found on screws (male threads), or internal, like the threads inside a nut (female threads). Taps and dies are common examples of threading tools for these purposes. For high-volume production, thread rolling machines are preferred due to their efficiency and the enhanced strength of the threads they produce through work hardening and maintaining material continuity.
Uses of Threading Tools
Threading tools are essential for producing threaded components by cutting material on a lathe. While this method offers precision, it is more time-consuming and generally produces weaker threads compared to thread rolling, which enhances the material’s hardness and strength. Thus, cutting threads with these tools is typically reserved for low-volume productions, such as prototyping or creating large, uncommon thread sizes that are impractical to achieve with standard taps and dies.
Principle of Threading Tools
In lathe operations, threading tools carve spiral thread patterns by turning the workpiece against the tool’s cutting edge, which is held perpendicular to the workpiece. Precise control over the depth of each cut and the number of passes is critical to achieving the desired thread pitch and profile.
Generally, multiple shallow passes are recommended to gradually form the thread and ensure a clean, accurate finish. Both external and internal threads follow this basic procedure, though machining internal threads requires additional skill due to the limited visibility and access inside the workpiece.
Other Information on Threading Tools
Rake Angle of Threading Tools
The rake angle—defined as the angle between the cutting edge of the tool and a line perpendicular to the workpiece surface—plays a critical role in thread machining. Due to the helical nature of threads and the resulting lead angle (the angle of thread inclination relative to the screw axis), threading tools must have differing rake angles on their left and right cutting edges to accommodate this geometry.
Proper maintenance of these angles is crucial for effective cutting and requires precise grinding to restore sharpness after wear. This understanding is essential when re-sharpening the tool to ensure that the specific demands of thread cutting are met, including the unique adjustments needed for the tool’s left and right sides.