Cutting hole through concrete???

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  #1  
Old 03-20-07, 02:14 PM
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Cutting hole through concrete???

I need to punch a 3 inch round hole out through my concrete foundation for a bathroom vent in my basement... What is the easiest/cheapest method for the hole? Is it possible to hammer drill several holes in the circle and smack it out with a hammer?

thanks,
Craig.
 
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Old 03-20-07, 02:37 PM
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if you don;t have any rebar running through that exact spot, then yes you can do it as you suggest.

You can also wet core or dry core drill a hole iin the wall. You may be able to rent the neccessary drill motor and bit. (if water runnning down the wall while you are drilling is ok, I'd go for the wet one)

btw: several isn;t going to cut it. More like several DOZEN.
 
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Old 03-20-07, 07:58 PM
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Do you want easy or do you want cheap? They are seldom inclusive.

Easy is a hole saw, probably 150 bucks and an hour.

Cheap is a drill, a bunch of holes, and a chisel and hammer, along with something to cut the bar when you hit some. Figure a full Saturday in beer hours and 50 bucks worth of tools if you don't have them.
 
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Old 03-21-07, 04:37 AM
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I agree. I've cut a lot of holes in concrete and a rented core drill is the way to go. It would take about 5 minutes or less and leaves a perfectly smooth, round hole, and will go through rebar as well. You can get the bits in many diameters. Usually you need water though, so if the runoff will be a problem you've got to figure a way to contain it.
Another option is a rented roto-hammer (not just a homeowner's hammer drill). Get the largest bit that will fit it, and a chisel attachment too. Drill multiple holes as you suggested and then use the chipping mode and chisel to clean it up.
 
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Old 03-22-07, 08:29 AM
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Thanks for the info....

I think I will rent the wet-bit core drill... will that cut through wood as well? I have a joist right in front of the concrete - would be easiest for me to just go through all at once - if possible...
 
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Old 03-22-07, 12:56 PM
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I suppose the diamond tipped bit would eventually burn it's way through the wood, but it would be slow. The bits do not have a sharp edge like a saw blade. They don't "cut", but instead grind their way through the concrete. It would be a lot faster to use a hole saw of the same size as the core drill bit (or a little larger) to cut through the wood first. Or just notch the wood out with another type of saw. Then go with the core drill for the concrete.
 
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Old 03-26-07, 09:11 AM
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I went to our rental centre and they had either this huge drill and wet coring bit that I actually have to anchor to the wall which will cost around 175 and then they have a smaller hilti with a more shallow bit for 50...

Any opinions?
 
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Old 03-26-07, 02:33 PM
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somebody probably should have told you the wet core setup is essentially a drill press that needs to be mounted on the wall. I have never seen a hand held wet core setup, maybe some of the others have. Sorry about that.


If the Hilti setup is what I think it is, the bit has carbide teeth (probably 1 or 2 dozen) around the perimeter of the bit. If so, this is nothing more than a impact hole saw for concrete. If you run across rebar in the wall, this will not cut it. As a matter of fact, it could even damage the bit (which I would guess you would have to pay for).

The wet core setup is the way to go, still. You do have to set anchors in the wall to hold it to the wall.
 
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Old 03-26-07, 03:43 PM
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Making a series of small holes then smashing out the middle is certainly cheaper but your hole will be larger that you want and would need to be grouted after.

If they are going to charge you $175.00 to rent the core drill I bet you could find a plumber who would do it for under $250.00........ especially if you paid cash.
 
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Old 03-27-07, 05:09 PM
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OK I get it now....

I am going to need a new furnace in the next year or 2, I will just rent the thing and drill the extra 2 holes I am going to need for the furnace at the same time.

The $175 isn't too bad if I am going to drill 3....
 
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Old 03-27-07, 05:26 PM
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I did just recall something else you may be able to find.

There is a vacuum base wet core drill available. It uses suction to hold it to the surface being drilled. It works for most relatively smooth concrete. You wouldn't need to drill for anchors.

Don't know if you can find one to rent though.
 
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Old 03-27-07, 05:40 PM
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I have only used the vacuum base on flat work. Will it work on walls?
 
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Old 03-27-07, 06:03 PM
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Originally Posted by Tscarborough View Post
I have only used the vacuum base on flat work. Will it work on walls?
the one I used would. You have to think, it will hold against the pressure you apply with the quill (which I must admit sometimes I get a bit carried away) but that does apply quite a bit pf pressure in normal use even, especially when you are boring a 4 or 5 inch hole in 8+" 'crete. Lots of torque applied to the base with that.

the leverage of the unit didn;t seem to be a problem, but you better have somebody to help you when you kill the vacuum 'cuz it's gonna fall like a rock.
 
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