# Drilling Exposed Aggregate?



## cbzdel (May 11, 2010)

What is the best way to drill into exposed exaggerate concrete? I am going to drill in a bunch of these guys:








Last time I did it over exposed aggregate at a friends house the bit wanted to walk like crazy which made it very hard to drill accurately.. 

Anyway to more precisely drill these? I will be drilling 52 holes in this exposed aggregate so the more accurate the better. I do have a roto hammer as well, the issues is not my tool is the bit itself walking on the aggerates before it starts to actually drill.. 

I will be using a 1/2" bit. I was thinking I could just drill a 1/2" hole into a long 2x4, align it over the proposed hole location, and stand on the 2x4 so it cant move, and then just start each one of the holes??


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## mako1 (Jan 7, 2014)

They 2X4 won't get it.It will pull off even with your weight on it.Get a heavy center punch and 3 # hammer and Start a good center for each hole.If you put one in 2 corners for the bracket and then screw it in you should be good to go.


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## stadry (Jun 20, 2009)

*or* start w/carbide drill & jacobs chuck on a drill THEN switch to a rented bosch bulldog hammer/drill

irc


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## mako1 (Jan 7, 2014)

With all due respect to itsreal,a Jocobs chuck is nothing more than a brand name for a drill chuck.They hold the bit.Has nothing to do with the drill slipping off of exposed aggregate.
You need a flat spot to start drilling or a indent to keep the drill bit from slipping.
A center punch and hammer will give you this.


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## stadry (Jun 20, 2009)

& all this time, i thought 'Jacobs' was a type of drill bit chuck that isn't worth a **** when used in a hammer drill OR rotary hammer,,, what's why we have sds, spline, hex, taper, & square chucks,,, is ' Jocobs ' a different style ? may be different than i know OR a typo

coult always use a ball peen hammer & break the offending aggregate 1st,,, ctr punch & hammer OR just a hammer,,, no one's going to get down on their hands 'n' knees to look at the work, are they ?


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## cbzdel (May 11, 2010)

so if I just pick up a punch style chissle and punch flat 2 of the 4 bolts and attach the bracket then drill the remaining 2 holes using the bracket as a guide I should be good to go in your opinion? just wanted to make sure I was understanding correctly?

I really never though of using anything to chip away the rock beforehand haha.. Not to mention the bracket should be covering everything after the fact.


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## mako1 (Jan 7, 2014)

There all types of different chucks including the ones you mentioned.Jacobs is still a brand.
My answer was to the HO question.The bit is not slipping in the chuck.It's slipping off of the exposed aggregate.No matter what chuck you use.
I don't think anyones going to get on their hands and knees to inspect the work.I was just trying to answer the HO question on how to solve the problem they had.


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## Bud Cline (Mar 12, 2006)

In my thinking it would all depend on the make-up of the exposed ag. There is more than one way to do exposed ag.

No telling how much ag will be disturbed down inside the hole. May not be reliable when it comes to getting an anchor bolt to expand and bind and stay in place.

I would think about using a core saw and cutting/sawing a "one inch" or "one and a quarter inch" hole, then set the anchor bolts in expandable pourable bolt-anchor product such as Pour Rock or something like that.


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## mako1 (Jan 7, 2014)

Good point!The surface is the easy part.Can't see past that.


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## Bud Cline (Mar 12, 2006)

A coring saw doesn't use percussion to vibrate the hell out of things and maybe compromise the integrity of the surrounding aggregate. If I were doing this as a contractor and had some liability in the matter I would absolutely core it.:yes:

The more I think about this... I'm thinking I would also pre-install the bolts into the shoes using a jamb-nut below the plate and plug-in all four bolts at the same time.


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## mako1 (Jan 7, 2014)

I have cored a lot of them in the past and used parabonds to secure the bolts.DIY'er won't usually follow this or got to the expense and trouble.


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