55 Deg Insert (DNMG 331 F1)

Designed for cutting hard materials like tool steel, this ceramic insert tool holder features a triangular insert mounted at a negative rake angle. The downward tilt of the insert provides proper side clearance, allowing you to use all six cutting edges—three per side—before needing a replacement. The 3/8" shank fits Sherline’s P/N 7600 tool post (not included). A clamp, hold-down screw, and 3/32" hex key are included for secure installation. Replacement inserts are available as (P/N 22659).

Why Use Ceramic Inserts?

Ceramic cutting tools are a powerful addition to the modern machinist’s toolbox. Though more brittle than high-speed steel (HSS) or carbide, ceramic inserts excel at cutting hardened steels and other tough materials, especially at higher spindle speeds. This makes them ideal for jobs that would otherwise be extremely difficult or impossible—such as turning down the shank of an end mill.

This insert’s large nose radius helps achieve an excellent surface finish, particularly when profiling.

• Each insert offers six usable cutting edges:

  • Rotate 120° to access a new edge (3 per side), then

  • Flip the insert for 3 more cutting points on the opposite face

• In comparison, traditional carbide inserts offer only 2–4 cutting edges, making ceramic inserts cost-effective over time, despite the higher upfront cost.

Usage Notes & Safety Information

• Ceramic inserts are brittle and should be used with proper technique to avoid chipping or breakage.

• Caution: Chips produced during cutting can be extremely hot—even red-hot. Use protective eyewear, gloves, and fire-safe clothing when operating.

• Some materials, such as tool steel, may form long, stringy chips that wrap around the part ("bird’s nest" effect).
  Use a chip brush and stop the machine frequently to clear chips. These chip clusters can ignite if they come in contact with hot chips.