On Sun, 19 Nov 2006 21:59:36 +0000, Grunff wrote:

Use a tile bit to make the initial hole, then switch to a 16mm masonry
bit. This works fine on ceramic tiles. If porcelain, you need a diamond
core.

For a 22mm dia hole I used a Dremel to enlarge and smooth a hole made by
piercing the tile with a tile drill. I guess it work just as well for a
smaller hole.