For PH Stainless Steel (17-4, 15-5, 13-8) as well as Titanium Alloys, Nickel Based Alloys and Cobalt Alloys we recommend the Helical 7 Flute Variable Pitch End Mill with TPLUS Coating where available (for Diameters under 1/4" we recommend the 5 Flute Variable Pitch & APLUS Coating when TPLUS is not available). The Variable Pitch will break up Harmonics and the 7 Flutes will give you the best combination of Tool Life, Cycle Time and Chip Clearance. Make sure to take a stepover at 7%-11% of the Tool Diameter and go utilize Helical's Milling Advisor for Speeds/Feeds.
Step 2: Select a End Geometry (a Radius is Always Recommended and is the First Choice in HEM. In 1/8" & 3/16" Tools choose .010" Corner Rad, In 1/4", 5/16" & 3/8" Tools choose .020" Corner Rad, and in 1/2", 5/8" & 3/4" Tools choose a .030" Corner Rad):
