center punch

from WordNet (r) 3.0 (2006)

center punch
    n 1: a tool with a conical point that is used to make
         indentations in metal (especially to mark points for
         drilling)
    v 1: make a small hole in something as a guide for a drill

from The Collaborative International Dictionary of English v.0.48

Center punch \Center punch\, or Centre punch \Centre punch\
   (Mech.)
      (a) A punch for making indentations or dots in a piece of
          work, as for suspension between lathe centers, etc.
      (b) A punch for punching holes in sheet metal, having a
          small conical center to insure correct locating.
          [Webster 1913 Suppl.] Center seal