Drilling concrete

FlameOut · Aug 6, 2009

Why is is such a pain to drill concrete? I'm trying to install my MaxJax and it's already taken me a few hours and 1 dead drill just to do a few holes.

I burnt up my Dewalt hammer drill, so went and bought a Bosch (not made in China) hammer drill. This thing gets so hot I can't even touch it.

I'm also having problems with bits. I had a heck of a time finding a 7/8" bit. Found one that will drill 4" but need to go 5 1/2" so I bought the only one they had a HD, a Bosch SDS bit. Of course my drill isn't for the SDS bits, so I can't even tighten it down properly where it isn't wobbling.

My concrete is only about 3 weeks old, so I thought it might be a little easier to drill than it is. I know I'm not hitting rebar. I had it all marked out, and also rechecked rebar location using a metal detector

Are there any tricks, like maybe have a trickle of water flowing while drilling?
I'm about to head out now to buy my 3rd 7/8" bit. I've been drilling with a 3/8, then to the 5/8 and finally the 7/8"

TONE · Aug 6, 2009

Ive got a hilti hammer drill. it goes thru all concrete like butter.

have ya tried doing a pilot hole first? meaning a very small built, like for tapcons?

twostory · Aug 6, 2009

I rented a Hilti hammer drill as Home Depot. They supply the bits. This monster drill put a 1/2 inch hole into my concrete almost at fast as drilling wood. I was drilling 4 inch deep holes.

I suggest you rent a bigger drill.

Ripcurl · Aug 6, 2009

What mpa is the garage slab? Typically they are 32, but it should still be easy to drill through at that. If you have something like 50 then thats your problem right there. I've managed to drill through a bank vault :ninja:

which I never saw specs for the mpa. My Miluwakee hammer drill ate through it with no problems. Then again I was using 1/8" to 1/4" bit.

I see guys on site using corded hilti hammer drills with at least 3/4" bits. They work through anything with barely working a sweat.

How much do you weigh?

tatra · Aug 6, 2009

forward/reverse switch? :lol_hitti

rsanter · Aug 6, 2009

generally going into the concrete is easy, some of the rocks (agrigite) you hit is not so bad but some of the rocks in the concrete are hard as hell.
generally if I have any trouble I drill a smaller hole first and then step up

bob

FlameOut · Aug 6, 2009

I've been using smaller bits working up to the 7/8. I just bought another 7/8" bit with a smooth shank. Doesn't wobble like the SDS bit, but it seems to work it's way lose and then the chuck just eats away at the shank of the bit. I'm going to take a break for a while. I just burnt the hell out of my finger touching the chuck of the drill. I'll let it cool of r w hole

Not sure what MPA is or for that matter what it even means. I know it's 4000psi slab and between 7 and 8' think. I think I might go check on renting that Hilti. For what I spent on bits I could have probably saved money (over $60 for 2 7/8" bits)

TONE · Aug 6, 2009

are you using a real hammer drill or a regular drill that has a hammerdrill setting?

if so, its your drill is just to weak. thats probably why the bit is coming loose.

my hilti was bought for hanging large commercial signs onto building. it walks right thru concrete.

I think you need a bigger-stronger drill. go rent one. about 40 bucks at homedepot.

boiler7904 · Aug 6, 2009

Mpa is the metric version of psi.

Rent the right tool (and attachments) for the job if you don't already own them.

Hammerdrill bits (SDS, SDS+, standard shank) are tool / chuck specific. There are adapters available for some combinations. Trying to use a SDS bit in a standard chuck isn't going to work as you already learned. I'd try skipping the smaller bits and go right for the 7/8".

russlaferrera · Aug 6, 2009

I found if you hit a stone the drilling stops. What I do is use a star drill and hammer to break up the stone, then continue drilling. You should not be having a problem drilling. Have you checked drill rotation ? Is the bit secure in the chuck?

FlameOut · Aug 6, 2009

I ended up renting a Hilti from HD ($32) Didn't come with any bits, but my 7/8" fit ok. It was easier, but by no means easy. I'm still about ready to cut this MaxJax up for scrap. I have over 20 holes in my new $4000 floor. I followed the directions for installation, but when I went to bolt it down, the holes didn't line up. Did that twice!

I already spent over $75 for additional anchors, now I need 5 more, and to make things worse, now I'm hitting rebar in two of the holes, and of course it's about 4" down, not quite far enough do install the anchor

jkeyser14 · Aug 6, 2009

FlameOut said:
I ended up renting a Hilti from HD ($32) Didn't come with any bits, but my 7/8" fit ok. It was easier, but by no means easy. I'm still about ready to cut this MaxJax up for scrap. I have over 20 holes in my new $4000 floor. I followed the directions for installation, but when I went to bolt it down, the holes didn't line up. Did that twice!

I already spent over $75 for additional anchors, now I need 5 more, and to make things worse, now I'm hitting rebar in two of the holes, and of course it's about 4" down, not quite far enough do install the anchor

If you get so fed up that you do decide to get rid of it, hit me up and make it worth my drive to Pittsburg :bounce:

.

But honestly, start by carefully marking the hole locations with a sharpee. after you have the locations marked, put the post on top to verify that it looks right. If it does, start by drilling a SMALL pilot hole. I would start at 1/4". Once you have that, switch to the big bit.

Drilling concrete

FlameOut

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TONE

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twostory

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Ripcurl

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tatra

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rsanter

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FlameOut

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TONE

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boiler7904

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