Overview The CNMG 120408-PF 4225 is a double-sided, negative-rake turning insert from sandviks Coromant's T-Max® P range. It uses the 12.7 mm (1/2") 80° rhombic body with a 0.8 mm corner radius — the most widely used radius in general turning — paired with the PF finishing chipbreaker . R0.8 is the practical default for a reason: it is strong enough to survive semi-finishing feeds and light interruptions, yet fine enough to hold surface finish and tolerances on most medium