I need to punch a 2″ hole through an 11″ foundation wall. I called some local rental companies and found three options. One wants me to rent a large core drill that anchors to the wall or floor ($100), another wants me to rent a handheld Hilti drill and 2″ core bit (actually only 7″ long, so includes a 12″ 1/2″ bit as a guide for the other side) ($60) and the third wants me to rent a large handheld hammer drill and core bit ($40).
The hole doesn’t have to be perfect, but I don’t want to make a mess either. Can I get away with one of the handhelds or should I rent the large anchored one?
Replies
all three will do it. it fact I have all three in my tools arsenia. I think I just use a hammer drill with a 12 inch long 1/2 inch bit. coring sideway is not much fun with a core rig.
I put a 2 1/2" hole thru 22" of concrete, on a 45 degree angle downward. Did it with a Relton bit on a Bosch rotary hammer, hand held. It's not really a coring operation, it pulverizes the concrete, so you have to stop and shop vac the dust out from time to time. It gets really hot if you don't do it often enough. The coring rig uses a diamond hole saw, much more expensive than the Relton.
-- J.S.
I use a concrete cutting company, they have the tools for it. Let them do it!
MRinger said what I would have first.
Core drilling, especially for a 2" hole, has an advantage in that the coredrill is (slightly) better at coping with rebar that is not where it's supposed to be (one more place for experienced concrete cutters to excel).
The core drill makes a nicer exit hole, just about bar none. Even on a "does not need to be perfect" job, I think it's good practice to start the hole from both sides, if only for a neater job with no tearout. But, that's me, others differ.
Question the rental outfits about who is responsible for broken teeth on those bits. They get very pricey. Oh, and the local guys here also charge for bit wear...they measure the bits with a caliper before and after you rent.
Might be cheaper to hire a concrete cutting out fit.
Poured foundation?
There are no electrons! It is all made up. Don't believe it.
Electricity is made by GREENIES.
Make sure you need a two inch hole and not a 2-1/4" or so. Easier to grout in than to ream out.
I'd get the Hilti probably, but
how high up is this?
how close to the bank? ( the dirt bank, not the savings bank)
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
related question, when core drilling curbs for drainage is there a maximum core size or a minimum space you need to leave to the top of the curb so it doesn't just crack out? Is there a best practice here?
The older coring machines are anchored to the wall with an expansion anchor. The newer, better ones use an air vacuum pump to hold onto the wall by suction. That's the type to get. They also need water, so there'll be two power cords and a garden hose down there in the hole with you. But it will do a very nice job with relatively little effort on your part once the setup is done.
The quick and dirty way to do it would be to get a long 1/2" bit and drill holes through as close together as possible around the circumference of the hole. Then knock out with small sledge or chipping bit in same rotary hammer. If the hole must be in a specific location then you will be SOL if you hit rebar whilst using the drill-and-bash method. OTOH, coring machine will cut through the rebar.
I'm either lazy or have other things to do, so I get a concrete cutting company like some of these other guys. Your job would be a minimum charge, so at least do yourself the favor of calling a couple of cutters and seeing what their minimum charge is. You could do it yourself with any of the tools you mentioned, but it will probably be serious aggravation.
Ended up renting the 2" core drill with the water hookup. Ended up hitting a piece of rebar and took about 15 minutes grinding through it. You were right about them measuring the bit, charged me an extra $25. Live & learn. I hate soggy socks.
What was the total rental cost including the tool wear?
$123. It was supposed to be $100 plus $5 tax. The local rental places didn't have anything I liked and this place is 30 miles away, but very close to work. They had a cheaper half day rate, but getting it back in time would have meant an extra trip, which would have burned up the savings in gas and time. I left work a few minutes early, picked it up, drove home, was done in a half hour, then returned it the next morning before work. They charge a full day rate if you keep it overnight.
we have one here that is closed on weekends but if you rent friday afternoon and keep till monady morning, only one day rental.
Drilled a lot of those size holes in the 1970s putting rock bolts in the walls of Minuteman silos for nuclear shock upgrades.
Choice of tools depends somewhat on your foundation wall concrete, probably less than 3000 psi stuff, so the hand held rotohammers will do.
Stuff drill in MM was 6000 psi concrete with 3/4 rebar at 2" on center web, diamond core drill was about the only way to go.
DIY at home have done simlar holes with just an air impact chisel.
PS: Note mentioned in any of the other responses or end result was using an oxy-acet torch - just 'pop' your way thru, can cut rebar too!
Edited 11/9/2005 7:56 am ET by junkhound