Case hardened steel is metal that has gone through heat treatment. This process results in a hard exterior to the metal article. Vehicle components such as driveshafts are made with case hardened steel. Pistol and rifle barrels are also fabricated with this type of steel. Drill through case hardened steel using a drill press and special drill bits made for metal. An oil lubricant will help with the drilling process and will keep the drill bits from breaking.
Grind the surface of the steel where it needs to be drilled. The area that you grind is no bigger than the hole that needs to be drilled. Grinding of the surface on case hardened steel removes the hard casing allowing it to be drilled easier.
Position your case hardened steel piece in the vice and place the vice on the drill press. Position the piece so the hole that needs to be drilled is aligned with the drill bit.
Drip two drops of hydraulic oil on the steel and slowly drill into the steel with the drill press. Continue dripping hydraulic oil on the metal as you proceed through the drilling process.