How to drill a 4" hole in cinder block


Ok I know i can drill a whole load of little holes in a circle and then knock it out, but is there such a thing as a 4" drill bit that will do this more easily?
Thanks!
DeanB
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dean wrote:

versions. The cleanest, most efficient, and easiest drilling is a wet diamond bit. Problem is, the cost hundreds of dollars, and require either a special drill that directs water into the center, or a water swivel attachment for a conventional drill. Dry core bits work much slower, and cost a lot less. Do you need a very clean & accurate hole? If not, save your money & punch it out with a series of 3/8" holes & a chisel.
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Yeah. Try larger builder merchants and/or plumbers merchants. They can be quite expensive, so try to befriend someone who can get wholesale.
Over in England they range from 20 to 100's, but my father got one from a "wholesale" buddy for less then 10.
Having said that, if it's just one hole, then i'd be tempted to just do the pin cushion drilling as you described.
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Drill a series of small holes and then punch the core out. Purchase a half round bastard file. The file isn't meant for concrete but will do a nice job in smoothing and accurizing the hole. You may have to throw the file away when done, but it will work.
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hamilton tool beaver falls pa sells surplus diamond core bits fo 25 bucks a inch, a real bargain.....
they sell mail order and are good to deal with
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On Tue, 14 Nov 2006 16:52:42 -0500, snipped-for-privacy@mucks.net wrote:

Do they sell card files anymore? I've not noticed one.
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Why not just punch a cinderblock-sized hole with a 5 pound mallet, and then stuff mortar in everywhere that's not part of the 4" hole?
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Leave it to the architect to go with a figure/ground study. ;)
R
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dean wrote:

1/2" SDS hammer drill and a cold chisel. 4" is nothing.
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I've looked at chisel bits for my 1/2 inch Bosch hammer drill and wondered if they could make a hole that is anywhere close to round. Can the chisel bit actually be used for making round (or close to round) holes?
Thanks, Smarty

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Smarty wrote:

Rough it out maybe 1/2" undersized and clean it up. It's masonry work, it's going to be rough.
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Thanks for the advice. I did not know how the chisel bits were used and know I understand. Thanks again!
Smarty

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Father Haskell wrote:

enough, you could look in the yellow pages. there are companies out there that cut and drill concrete. you might even be able to rent a bit.
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Try here: http://www.dynatech-diamond.com/dynatech/showprod.cfm?DID=7&ObjectGroup_ID=6&CATID=4

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dean wrote:

I've seen a lot of recommendations for various drills, but what about marking the hole and using a rotary zip saw to cut it? I'm sure there are masonry bits available for those larger zip saws, considering even my little Dremel tool has such a thing for small masonry cuts.
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As others have suggested, renting a core drill, or using a hammer and appropriate chisel are the simplest way.
I have, however, watched experienced electricians punch 2" conduit holes in cinderblock with nothing more than a 2 pound hand sledge. Not perfectly circular of course, but close, and you have to seal it anyway.
I probably shouldn't recommend that tho, unless you have something to practise on ;-)
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
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Drilling holes around the circumference is the easy way to do it. You don't need additional tools and expenditures and it's almost as quick as a core bit. If you have a 4.5" angle grinder with a diamond blade you can clean up the hole to make it rounder. It'll make more dust that you'd believe, but it will do it just fine.
R
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