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4" Hole In Concrete

 
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Old 10-22-2018, 03:44 AM   #1
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4" Hole In Concrete


I need a bit to drill two - 4" holes in reinforced a concrete (floor) with an SDS MAX arbor attachment, it has to be able to cut dry ...any suggestions?
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Old 10-22-2018, 07:16 AM   #2
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Re: 4" Hole In Concrete


If you've already decided to use a hammer core bit get whatever you can get a good deal on...Bosch, DeWalt, Makita, Champion...they are all really similar. Just don't hit rebar or you're boned.

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Old 10-22-2018, 08:17 AM   #3
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Re: 4" Hole In Concrete


Local tool rental co, last time I needed to do the same I rented the drill and stand along with the coring bit.
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Old 10-22-2018, 11:41 AM   #4
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Re: 4" Hole In Concrete


I've done it through an 8" wall with a Milwaukee SDS bit and one of their cheaper corded roto hammers and it was a royal PITA. Hit rebar twice. Took forever. Didn't even come out that clean in the end.
If you have any way to map out where the rebar is to avoid hitting it, by all means do it!
The rotohammer and SDS bit will work, but renting a bigger unit and a proper coring bit might be the way to go.
Also, if you have to go dry, vac it, isolate it, vent, air scrub...do whatever you can to keep the dust down and out of your lungs. Silica is the new asbestos.
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Old 10-22-2018, 02:12 PM   #5
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Re: 4" Hole In Concrete


why not just sub it out to a concrete cutting guy.

they have all the toys & it will be on them to bore the holes, not you...
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Old 10-22-2018, 04:11 PM   #6
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Re: 4" Hole In Concrete


Use a Very high pressure tank of N2, Argon, or CO2 to cool the bit, make sure you have plenty of fresh Air/O2 blowing in the space, dry vacumn on dust control.

Flow rate = amount needed to cool the Wattage of the drill motor plus a little for wastage.

Cut a 12-14" square opening with a 12-14 " diamond bladed electric/air/hydro Demo saw plunge cutting, install sleeves, repour concrete....
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Old 10-22-2018, 06:17 PM   #7
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Re: 4" Hole In Concrete


Quote:
Originally Posted by griz View Post
why not just sub it out to a concrete cutting guy.

they have all the toys & it will be on them to bore the holes, not you...
Yeah that seems like the best idea to me too... 4" is going to be some expensive tooling and miserable drilling.

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Old 10-22-2018, 06:59 PM   #8
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Re: 4" Hole In Concrete


Quote:
Originally Posted by Fouthgeneration View Post
Use a Very high pressure tank of N2, Argon, or CO2 to cool the bit, make sure you have plenty of fresh Air/O2 blowing in the space, dry vacumn on dust control.

Flow rate = amount needed to cool the Wattage of the drill motor plus a little for wastage.

Cut a 12-14" square opening with a 12-14 " diamond bladed electric/air/hydro Demo saw plunge cutting, install sleeves, repour concrete....
good idea, you do it that way. I will sub it out and he will be done in 2 hours and I will have 2 nice holes.
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Old 10-22-2018, 08:01 PM   #9
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Re: 4" Hole In Concrete


Bosch HC8550 4 In. x 12 In. SDS-max Rotary Hammer Core Bit https://www.amazon.com/dp/B0000TZYHA..._X.MZBbTBCKSCK

These work just fine as long as you dont hit rebar. The exit wound can get a little nasty. If it needs to be clean we have drilled a pilot hole all the way thru first, drill on one side about 1" deep, then go to other side of wall and drill thru to meet it.

Back in the day its all we had in our arsenal. We still have a huge, old, bosch rotohammer. Spline drive beast. 2 piece bits, shank and interchangeable coring bits and replaceable pilot bits. Ive punched many 5" holes thru solid concrete walls with that pig in order to run 4" conduit for Telco into comm buildings.

Nowadays, we use our dedicated coring rig for multiple holes that need to be nice and clean. We still use a rotohammer for the one offs.

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Old 10-22-2018, 08:16 PM   #10
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Re: 4" Hole In Concrete


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Originally Posted by Fixed View Post
Yeah that seems like the best idea to me too... 4" is going to be some expensive tooling and miserable drilling.

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If you can avoid rebar they actually work pretty well.
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Old 10-22-2018, 08:17 PM   #11
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Re: 4" Hole In Concrete


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If you can avoid rebar they actually work pretty well.
Yeah and few guys here seem to concur, so I guess I've got the wrong idea about it... Guess I was just going on my experiences with 2.5" holes and a rotohammer, and those don't scale well.

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Old 10-22-2018, 08:52 PM   #12
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Re: 4" Hole In Concrete


2 4" holes isn't that big of a deal, but if you don't own the bit, subbing it out might not cost much more and is certainly easier.
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Old 10-22-2018, 09:22 PM   #13
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Re: 4" Hole In Concrete


I think it’s about $400 minimum charge here, 2 4” holes through 8” or less would fall under the minimum charge rate.
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Old 10-22-2018, 11:21 PM   #14
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Re: 4" Hole In Concrete


i do not understand why any of you guys want to fool around with a trade outside of your wheel house, especially when you have to go rent specialized equipment....and it's a chitty job....

something unique, yea maybe....

but drilling big holes in concrete....wtf....

go do something else where you make some money...

and PLEASE DO NOT SAY "i don't have it in my bid"....

if that is the case go to work at a fast food joint....

and let the rest of us make some money....
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Old 10-23-2018, 12:22 AM   #15
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Re: 4" Hole In Concrete


A 4" hole in concrete is just a phone call away. It's going to cost you more to do it yourself. What Griz said!!


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Old 10-23-2018, 03:26 AM   #16
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Re: 4" Hole In Concrete


Quote:
Originally Posted by griz View Post
i do not understand why any of you guys want to fool around with a trade outside of your wheel house, especially when you have to go rent specialized equipment....and it's a chitty job....

something unique, yea maybe....

but drilling big holes in concrete....wtf....

go do something else where you make some money...

and PLEASE DO NOT SAY "i don't have it in my bid"....

if that is the case go to work at a fast food joint....

and let the rest of us make some money....
Because sometimes things aren't as straightforward as we would like them to be. I am building a new dentist office in an already constructed building. The dentist has to be in the new location by the beginning of December. The core drilling business around here are booked beyond that date. See my dilemma?
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Old 10-23-2018, 07:16 AM   #17
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Re: 4" Hole In Concrete


Quote:
Originally Posted by griz View Post
i do not understand why any of you guys want to fool around with a trade outside of your wheel house, especially when you have to go rent specialized equipment....and it's a chitty job....

something unique, yea maybe....

but drilling big holes in concrete....wtf....

go do something else where you make some money...

and PLEASE DO NOT SAY "i don't have it in my bid"....

if that is the case go to work at a fast food joint....

and let the rest of us make some money....
He's drilling a hole in concrete... not building a fvcking spaceship. He doesn't have to rent anything just spend 200 bucks on a bit. In the amount of time it took you to type all that negativity he could have the holes drilled.





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Old 10-23-2018, 09:20 AM   #18
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Re: 4" Hole In Concrete


I find myself doing things myself often because it's my job . It would take days to get someone to do a something that small mean while work stops while waiting for the sub . This year is extra special ,fence builder's were 3 months out ,my concrete truck is 1 month out .Getting help would be a challenge . My electrician doesn't answer ,the painter really doesn't want any more work .Which is how I feel . I am in the fire area .
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Old 10-23-2018, 10:09 AM   #19
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Re: 4" Hole In Concrete


Quote:
Originally Posted by griz View Post
i do not understand why any of you guys want to fool around with a trade outside of your wheel house, especially when you have to go rent specialized equipment....and it's a chitty job....

something unique, yea maybe....

but drilling big holes in concrete....wtf....

go do something else where you make some money...

and PLEASE DO NOT SAY "i don't have it in my bid"....

if that is the case go to work at a fast food joint....

and let the rest of us make some money....
While this can be good advice depending on the individuals situation there are also times where it makes sense to just do it yourself. I posted a question like this probably two years or so ago on here and got pretty much the same reply as you just gave. Due to having to work at night in an operating restaurant and other issues I ended up buying my own core drill and bits.

In the last two years I have made a bunch of money using the equipment I now own.

I can have the holes drilled faster then it takes me to call a company, have them come out and me have to explain to them where to drill. My plumber has his own core drill but my electrician doesn't so I will drill holes for him also and it works out good for both of us. There are many times when remodeling a business that I'll need a hole. Then a week or two later I'll need another hole due to things changing or something coming up. Works for me, change order and money in the pocket for an hour of work usually since the core rig is already on the trailer.

So ya some jobs are worth hiring out but it's also nice to be able to just do it yourself right away and move on. You have to pick and choose what makes sense for your particular situation.
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Old 10-23-2018, 10:43 AM   #20
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Re: 4" Hole In Concrete


I could get a concrete core guy to do it for 200 bucks. It would cost me twice that to have my guy do it. The bit and the labor. Not worth it. That's a positive message. Keeps more money in my pocket. A phone call and a little " x". Easy peasy.

And I can make a phone call faster than you can roll out your cord. Let alone drill and clean up.

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