Holes punched in a 1-inch steel plate would be drilled to size with which drill type?

• A. Twist drill
• B. Center drill
• C. Core drill
• D. Brad point drill

Answer: (C)

When finishing holes that have already been produced by punching, use a drill type that is designed to bring an existing opening to an exact, true diameter while preserving concentricity. A core drill is built to work with pre-formed openings, removing material around the periphery to finish the bore to the precise size you need. Its design helps produce a clean, accurate hole in steel without excessive wandering or misalignment, which is especially helpful after punching where the hole already exists but may need to be widened or cleaned up to final dimensions. The other bits have different primary purposes—center drills are for starting holes and creating center references on lathes, brad point bits are for wood, and a general twist drill is a versatile item but not optimized for finishing a pre-punched hole with tight tolerance in steel.