A burr includes a shaft portion and a milling portion. Cutters are separated by main flutes having a main flute depth. The cutters extend helically at a first twist angle. Each cutter has a cutting edge between a rake face and a relief face. The rake face forms a rake angle, and the relief face forms a relief angle. Chip breakers in each relief face have a chip breaker depth. 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 is between 3 degrees and +14 degrees, the relief angle is between 10 degrees and 20 degrees, the first twist angle is greater than 25 degrees, and the number of main flutes is less than 15.