Burr

A burr for an electrically or pneumatically operated, hand-held, or automatically operated tool for milling a metal surface, comprising:

• a shaft portion having an axis of rotation;
• a milling portion adjoining the shaft portion and ending in a milling tip, wherein the milling portion defines a largest diameter and a milling length;
• a plurality of cutters separated by a plurality of main flutes in the milling portion, wherein the plurality of main flutes have a main flute depth, and the plurality of cutters extend helically along the milling length in a first twist direction at a first twist angle α from the axis of rotation;
• each cutter of the plurality of cutters has a cutting edge between a rake face and a relief face, wherein the rake face forms a rake angle γ from a line perpendicular to the axis of rotation, and the relief face forms a relief angle δ from a line tangent to the cutting edge;
• a plurality of chip breakers incorporated in each relief face;
• the plurality of chip breakers intersecting with and extending from the cutting edge, to a position before reaching the main flute;
• wherein each chip breaker has a chip breaker depth, and chip breakers on adjacent cutters extend helically in a second twist direction with a second twist angle β from the axis of rotation;
• and
• at the largest diameter of the milling portion, the chip breaker depth is between 5 and 25 percent of the main flute depth, the rake angle γ is between −3 degrees and +14 degrees, the relief angle δ is between 10 degrees and 20 degrees, the first twist angle α is greater than 25 degrees, and the number of main flutes is less than 15.