Series Z1MPCR 4 Flute Variable Rake End Mills Corner Radius. The Z-Carb-AP offers performance so advanced, it goes way beyond typical high performance carbide end mills. With most 4-flute end mills, the cutting teeth enter and exit the material creating a natural rhythm that results in damaging harmonics. The harmonics produce a frequency that resonates through the entire end mill, resulting in chatter. With its patented, one of a kind geometry, the Z-Carb-AP offers three stages of chatter suppression: Superior chatter suppression through advanced patented design. Increase productivity by cutting deeper and wider without harmful harmonics Lower cutting forces for dramatically longer tool life.