Counterbores with 2 flutes type W group 0-1-2
in HSS hardness 63-HRC from Ø 7 to Ø 40.
Helix angle 28°.
You can fit them in all the Polledri mandrels of the same group.
With rotatory pilots or drills you can execute simultaneous operations. We advise them for materials with long and normal chip.