Any cement workers out there

[GOPHER SLAYER]

Yesterday I was trying to drill holes in our daughter's garage floor to anchor our SIL's gun safe. Now I have drilled cement to install floor anchors for over thirty years during my work at the phone company. That is how we anchored the equipment in place. It was never a problem with masonry drills, but not that garage floor. I have never encountered cement that hard. We were using new carbide bits and we could hardly make a little dust. I used a quarter inch pilot drill and it wouldn't go either. I should point out that I have drilled garage floors before with no trouble. My lathe was held in place with floor anchors. Are they making harder cement these days. Any ideas?

[Kimber1911]

Large electric hammer drill, not sure if you are trying to use a small cordless, but it seems to make a big difference.

[tomj44]

Rotohammer. And yes, much better concrete nowadays.

[Moleman-]

2nd a dedicated hammer drill that doesn't have a jacobs type chuck on it but rather some sort of . Best one I've used was a large Bosch with a spline shaft, but own a more useable size Milwaukee 5262 hammer drill at the moment that works well. Makes the hammer drill setting on my cordless drill seem like a joke.

[Winger Ed.]

Common household concrete is about 2,000 psi and has basically a soft river bed gravel in it.
It drills pretty easy.

If the aggregate is 1 & 1/2 inch granite, and the cement mix is high end stuff of 4-5,000 psi.
like they use on a interstate hi-way,,,, You'll need a hammer drill.

That's what we poured when I built our old house.
That stuff is harder than Chinese Algebra, but drilling into it is do-able.

A big Bosch or Hilti is best, and can be rented,
but a 1/2" Milwaukee will work with decent, round shank masonary bits..
If you can get 'Strong Arm' brand from someone that works on big TL rated safes, one will probably do OK.
If you get the big box store cheap junk, get two for each hole.

Get a pad for your shoulder so you can lean over on it as it hammers will make the project go faster.

Doing it without a hammer drill is possible.
However; bring a sandwich & something to drink, because you'll be there awhile.:bigsmyl2:

[GOPHER SLAYER]

Thank you gentlemen, you jogged my memory. I had completely forgotten. Toward the end of my career with the phone company, we went to hammer drills. Getting old I guess. BUGGA

[Pablo 5959]

You Probably hit Rebar or God forbid a post tension cable. If it’s a cable you’re lucky you didn’t kill yourself or somebody else.
I’ve seen cables shoot out the side of buildings from being drilled into.
Use a shop vac and a tube to clean the hole then see if you can tell which direction the rebar runs. Then decide to either angle the hole away from the rebar or drill a new hole.
If you find out it’s a post tension slab. Pour a new slab 6 inches minimum larger then the anchors with Rebar around the outside edge. Install your anchors into the new slab

[GOPHER SLAYER]

You Probably hit Rebar or God forbid a post tension cable. If it’s a cable you’re lucky you didn’t kill yourself or somebody else.
I’ve seen cables shoot out the side of buildings from being drilled into.
Use a shop vac and a tube to clean the hole then see if you can tell which direction the rebar runs. Then decide to either angle the hole away from the rebar or drill a new hole.
If you find out it’s a post tension slab. Pour a new slab 6 inches minimum larger then the anchors with Rebar around the outside edge. Install your anchors into the new slab

Pablo, you draw a horrible word picture. I think I will suggest to my son-in-law to anchor the safe to the wall with steel bracing on the other side.

[Winger Ed.]

If anybody there has a metal detector, steel anything is easy to locate in a slab.

Some big box stores rent them pretty cheap for people that lose a ring digging around in their flower bed.

[Pablo 5959]

Not to worry that much. There should be something in the closing papers or stamped in the concrete, warning (DO NOT DRILL).
It sounds like you found your problem if you don’t have a hammerdrill.

[Misery-Whip]

Now they make concrete bolt anchors that are removable. Ive used the style 3rd from the top.

4 of 1/2 or 5/8 x 4" are very strong. I run them in with a half inch cordless impact gun. But a ratchet works too.
https://images.app.goo.gl/bqPanz8uj2CzNkWs7

[Plate plinker]

I have used a SDS system for 20 years. Know nothing about post tension stuff, being I live in seismic stable Indiana. The normal concrete used here is 3500-4000 PSI. You can drill with a regular drill that has a masonry bit, if the hole is not to large or deep.

[jonp]

Yup, hammer drill. I bought a cheap one at Harbor Freight to drop expanding bolts into a footing and anchor a new knee wall I built under the porch. Worked quite well for that purpose.

[FLINTNFIRE]

I have used the harbor freight hammer drill and bits , bits are running strong still after 7 years drill has lasted till I used it to drill and break out a pad of reinforced hard concrete , now it will still hammer but bit will now come out when withdrawing from hole , was used a lot in drilling holes for anchors as carport pad has been turned into a add on shop . never had any luck drilling without a hammer drill in concrete at my house , tried a anchor screw in wall concrete with the drill sold for the screws , what a joke drill could not even start a hole , used the hammer drill and smallest bit and no problem drilling hole .

[jonp]

Yes, I wouldn't want to make my living with Harbor Freight power tools but for occasional use they seem to hold up pretty good..or most of them. Took back a power planer that wouldn't adjust and something else or other but I've had good luck with the hammer drill, orbital sander and cheap skilsaw I bought to use on cement blocks not wanting to use my Hitachi for that.

I've got a whole bunch of Harbor Freight tools for once in a blue moon use like a ball joint press, gear puller, hole saw bits stuff like that. No sense in buying Snap On for something I'm going to use every couple of years but good to have on hand just in case. I do have a 2500 Watt generator that starts in a couple of pulls and runs like a champ. Heavy but runs fine and that wire welder I got on sale for $90 works great and saved me over $300 paying for itself. Got several sets of HB wrenches but they sure don't hold a candle to my Made In America Craftsmans I have had for I don't know how long. The Craftsmans are twice as thick. I still managed to bend a 1in box end somehow. Must have felt froggy one day on a skidder or something.

[Handloader109]

The HF hammer drill I bought last year to drill holes (half inch chuck) works really well with their cheap bits. Way good torque.

[samari46]

I have a combination drill and hammer drill made by Bosch,when it bought it I also bought the Bosch concrete drill bits to go with it. Made in Switzerland. Buddy had a prefab building put up and needed some holes drilled. Went over and in about a half hour holes drilled and red head anchors installed. And this slab was about 4" thick and new concrete. Only been there for about a year and I heard the longer it sits and cures the greater the strength developes. If I'm wrong please correct me. When we got thhe new fuel oil tank alarm system installed they had to drill 4" holes in WWII concrete. Plenty of rebar and aggregate. Hammer drill was a waste. They had to go to a diamond core drill bit as the concrete was over 4' thick. Was a bomb shelter during the war and to protect the fuel oil transfer pumps installed early on in the war. Sidewalls were 4' and roof 4'. Floors were way more than 4'. Frank

[rancher1913]

the only tension cables I have ever seen were in multi story buildings to keep the floors from sagging, I highly, highly doubt that there a tension cables in your garage floor unless you have a room under it. the rebar is another story, you probably have a grid of it in a garage floor.

[Winger Ed.]

the only tension cables I have ever seen were in multi story buildings to keep the floors from sagging, .

We got 'em here.
I'd heard about them being used for houses, but never seen it done until I watched a house being built next door a couple years ago.

Probably a lighter version, but they were laid in, concrete poured, and a few days later a crew come out with
what looked like a real big drill motor, tightened 'em up, cut off some sort of a nub, and slapped a handful of cement on the depression.

[rancher1913]

you sure those weren't just wall ties on wall forms. what you describe sounds like a tension cable but that is way to expensive for most single family housing.

[NyFirefighter357]

There are two types of very hard concrete the newer high strength that sometimes contains fiberglass "hair" and hard aggregate up to 6,000 psi compaction & then there is very old concrete, that stuff poured 75-100 yrs ago can be just as hard to drill!

[nun2kute]

I've never done this before but you might just chech and make sure you got that drill running forward and not reverse

[6bg6ga]

I always used a Hilti large commercial sized hammer drill that weighed about 50 lbs or so. I used to drill 3/4 or 7/8" holes in concrete to install anchors for equipment racks. I doubt that your seeing any tensioned concrete. I used the commercial Hilti Drill bits available at the commercial/industrial products stores. I once drilled a 1/2" hole thru 30" of concrete in a basement of a 9 story building that was over 100 years old and even with the best bit it took time to get thru it.

[white eagle]

Bricklayer for 20+ years anchored a whole bunch of different items
if your drill aint cutting it check your bit make sure to use a new one
if that does not work get a bigger drill,not drill bit,especially if you are using
home maker drills go to a rental place and get an appropriate drill
there aint no concrete that can't be drilled for anchors