In article .com,
Chamblin wrote:

We have a porcelain tile shower and need to attach handicapped grab
bar. How do we drill this tile? Diamond bit? What do they cost? What
is procedure...small hole first then move to 1/8 bit?

Look he

http://www.diydata.com/tool/drillbits/drillbits.htm

Your bit is about three fourths of the way down the page; a carbide
tipped spear point. You can find these at any good hardware store,
maybe even Wal-Mart, etc.

Cost is $5-8 apiece, depending on size and quality.

You drill the final sized hole; no stepping up. Drill for screw
clearance plus a little for wobble. It is difficult to drill precisely
located holes with these bits.

Buy at least two. They wear fast in some ceramics. Heat from friction
is the biggest cause of failure. Keep the bit cool by dipping it in a
cup of water every few seconds. When it gets dull, throw it away and
use a fresh one. You are probably not equipped to resharpen carbide
tools.

Grab bars require drilling through the tile, its backing, and firmly
mounting into studs or solid wood blocking in the wall. I think code in
most places acknowledges this.

-Frank

--
Here's some of my work:
http://www.franksknives.com/