You don't need core box cutters these are for cutting a half round and are very short, you need the BDP tapered cutters 75 mm long 40 mm cutting length to get down to 50 mm deep,

BDP001B is a 1/16” diameter tapered ballnose with a 1” LOC on a 1/4” shank,3” OAL with 0.0312” radius and 3 degree taper per side Chipload .003 - .005

Phill