Drilling in concrete, impossible

ByggareBob! · 14 Jan 2018 at 5:51 PM

Hey!

I hope I'm posting this in the right place.

I tried mounting a TV on the wall this weekend; there are 5 holes that need to be drilled. I used my trusty hammer drill and a newly purchased drill bit from Clas Ohlson. The first hole in the concrete wall went okay. When I started on the second hole, it completely stopped after about 2 cm. I thought there was something in the way right there, so I tried 1 cm beside it, but the same thing happened. I tried another hole 1 dm away, and it was the same issue.
After some googling, I concluded that I need a rotary hammer, not a hammer drill, since it's a concrete wall. So, I gathered my last money from CSN today and bought this:
https://www.clasohlson.com/se/Borrhammare-Cocraft-HR710/40-8756
with these:
https://www.clasohlson.com/se/Hammarborrsats-Bosch/40-9272

To my great disappointment, I didn't get much further with that. I managed to get one hole but have 1 and 2 half-baked holes left. It completely stops, and I'm getting nowhere. They should be 10 mm holes and about 4-5 cm deep

Are there any tips for making these holes?

Stefan N · 14 Jan 2018 at 5:59 PM

It's if you've been so unlucky that you've hit rebar every time.

ByggareBob! · 14 Jan 2018 at 6:09 PM

Stefan N said:
That is if you've been so unlucky as to hit rebar every time.

Yes, I've read a bit about it, what does the hole look like if you've happened to hit it?
Is it something you can/should drill through?

Dub361 · 14 Jan 2018 at 6:17 PM

Just to rule out the basics, do you have the function dial in the correct position so that the hammer function is activated?

ByggareBob! · 14 Jan 2018 at 6:22 PM

D Dub361 said:
Just to rule out the basics, do you have the function knob in the correct position so that the hammering function is activated?

Yep, I've tried with just hammering as well as with hammering and spinning. Also tried with several different sizes, one hole went through because I managed to start with a 4mm drill first and then could use a slightly larger one to fit the plug.

henke_benke · 14 Jan 2018 at 6:25 PM

B ByggareBob! said:
Yep, have tried with just impact as well as with impact and rotation. Also tried with different sizes, one hole went through because I managed to start with a 4mm drill and then could use a larger one to fit the plug.

using just impact damages more than it helps. either rotation with impact or just rotation

ByggareBob! · 14 Jan 2018 at 6:27 PM

henke_benke said:
that using just power shots does more harm than good. either spin with power shots or just spin

Oh okay, Thanks, Very good to know

henke_benke · 14 Jan 2018 at 6:29 PM

it may be very possible that you hit reinforcement on the holes. can you move the hole (or all holes) vertically or horizontally?

ByggareBob! · 14 Jan 2018 at 6:38 PM

henke_benke said:
it might be very possible that you've hit reinforcement on the holes. Can you move the hole (or all the holes) vertically or sideways?

I'm afraid of that, is there a convenient way to prevent it?
Not too keen on drilling new holes and having the same issue, it would look quite unsightly in the bedroom

Husqvarna220Ac · 14 Jan 2018 at 6:43 PM

5 holes sounds like a lot, or is it a long arm/big TV? I usually drill with a regular drill when I go through rebar, but if you have a corded "Hilti" it usually can drill through these..keep drilling, keep pushing..

ByggareBob! · 14 Jan 2018 at 6:46 PM

H Husqvarna220Ac said:
5 holes sounds like a lot, or is it a long arm/large TV? I usually drill with a regular drill when going through the rebar, but if you have a mains-powered "Hilti," you can usually drill through these...keep drilling, press on..

It's a 42" flat-screen TV, but a pretty thick one. So it weighs quite a bit. This is the one that needs to be mounted:
https://www.kjell.com/se/sortiment/...parts-tiltbart-vaggfaste-for-tv-32-55--p57537
Okay, should I use a special drill then, one for steel?

Demmpa · 14 Jan 2018 at 6:49 PM

There is quite a big difference between various drills.
A drill with four cutting edges is usually better than one with two.
There are concrete drills that also easily drill through rebar, such as Hilti has a few different ones,
https://www.hilti.se/batteriteknik/instick/hammarborrkronor-(sds)/r4429

I have a few times been stuck working with cheap new drills without getting anywhere, and eventually, I went and bought Hilti drills that "smashed" through in no time.

Thomas_Blekinge · 14 Jan 2018 at 6:56 PM

Even the machine can be worn out.
I had a hammer drill that was barely able to drill regardless of the drill bit. A newly purchased machine did the trick. I assume that the mechanism that generates the blows can wear out and then the blows become less distinct and effective. Just a theory.

ByggareBob! · 14 Jan 2018 at 6:56 PM

Demmpa said:
There is quite a big difference between different drills. A drill with four flutes is usually better than one with two flutes. There are concrete drills that can also easily drill through rebar, for example, Hilti has a few different options, [link]

I have a few times been stuck with new cheap drills without barely making any progress, and finally, I have gone to buy Hilti drills which "mowed" through in no time.

That looks good, so there's no problem just drilling through it?

ByggareBob! · 14 Jan 2018 at 7:05 PM

Demmpa said:
There is quite a big difference between various drills. A drill with four blades is usually better than one with two blades. There are concrete drills that can easily drill through rebar as well, for example, Hilti has a few different ones, [link]

I have struggled a few times with new cheap drills without making much progress, and eventually, I've gone and bought Hilti drills that have "smashed" through in no time.

It doesn't seem possible to order from that site as a private person, and I can't find it anywhere else either. Do you know where it can be obtained?