When selecting thread turning inserts, the insert type, tooth flank/radial clearance, and insert flute shape must be considered. These factors affect chip control, insert wear, tool life, and thread quality.
There are three main insert types for thread turning: full-cut, V-cut, and multi-cut.
Full-cut inserts are used to cut the complete thread profile, ensuring the correct depth, root, and crest. Deburring is not required, and the larger tip radius reduces the number of passes. However, each pitch and thread profile requires a dedicated insert.
V-cut inserts do not machine the thread crest; the diameter must be machined first. They offer high flexibility and are suitable for various pitches, but the smaller tip radius shortens tool life and may produce burrs.
Multi-cut inserts have multiple cutting edges, reducing the number of passes to extend tool life and increase productivity. However, the increased cutting forces require stable operating conditions.
Insert flute shapes include flat flute, sharp flute, and chip-breaking flute, each suitable for different materials. Flat flute is versatile, sharp flute is suitable for sticky materials, and chip-breaking flute is suitable for materials with long chips. The tool shim is used to impart a tilt angle to the cutting tool, making the cutting edge angle equal to the thread helix angle. Its selection depends on the lead and workpiece diameter.
