The parts that aren't grinding now won't make a difference as long as they aren' too many (like more than 20% of the area of the tool) that aren't hitting the surface.
Personally, I leave the casting of the tile tool until the glass is about 80% of the depth and fairly spherical and do the casting right on the glass. The iron tool is used to just make the hole and I usually use a ring tool, usually in the shape of an end cap for some iron pipe.
I really haven't done all of the grinding with an iron tool but it's another way to do so. The professionals do it this way with solid iron tools.

• Re: Cast tool grinding - jkoptic - March 30, 2002 - 04:26 UTC
  • Cast Tool Experiment - imacca - April 1, 2002 - 16:18 UTC
    • Cast tool - bobmay - April 1, 2002 - 19:37 UTC