What do I use to cut holes in cement board

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.
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you're supposed to cut them with a utility knife and punch it out with a hammer.
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poison snipped-for-privacy@yahoo.com wrote:

"Hole saw"
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wrote:

you can do it either way but I've found it easier to punch it with a hammer
http://www.cgcinc.com/pdf/howtos/EDR_6209.pdf
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On Nov 1, 10:20 pm, poison snipped-for-privacy@yahoo.com wrote:

They have coping saws with round carbide-covered blades.
--Jeff
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Or how about one of the roto-zip type spiral saws?
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Masonry bit? You can use a small one and drill multiple holes for smaller openings, then break out the middle. Or drill corner holes and use a carbide blade in a sabre saw. You can use regular steel bits and blades, but they won't last long. A 1/8" carbide cutting bit in a dremel tool or other high speed tools works very well. For longer straight cuts, score and break, or used a masonry abrasive blade in a circular saw (but don't breath the dust).
Bob
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On Nov 1, 9:20 pm, poison snipped-for-privacy@yahoo.com wrote:

Harbor Feight has carbide coated hole saws that should make short work of any of the cement boards. Even diamond in 7/16" and 3/4" sizes for $3. Cat # 32399-9GBG. Latter ought to last quite a while. HTH
Joe
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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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