It is hard on regular hole saws, but they work quite well. It is
often easier to get an oversized piece of scrap pipe, support the
sheet well, and punch the pipe through the sheet with a hammer.
This method works just as well on drywall.

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______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




wrote in message
s.com...
Durock, hardi-backer, wonder board etc. I assume some type of
carbide
drill bit but what is it called? Holes big enough for pipes and
shutoff vales. Thanks.