Drilling into concrete wall questions

Submitted by Sleepy_C t3_zxh8wr in DIY

Hi there. Wife & I moved into a new UK flat. We decided to wall mount our TV, and discovered that the wall is just dry wall & cement. The mount comes with plugs and instructions for cement mounting, so we decided to go ahead.

I've mounted a lot of things in studs before but never used plugs and done cement drilling.

We have a drill bit for cement, steel and ceramic that's the right size for the plugs. But when we go about 1.5cm into the wall it just starts spinning and we don't make anymore progress. I need another 2 or 3 times that to fit the plugs. Is there something I'm missing with cement? I'm using a very simple drill, so maybe it's a power issue or the type of drill but I'm not familiar with this sort of stuff.

Any help is appreciated.

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hidrate t1_j208jxg wrote

You need a hammer drill to penetrate into concrete and masonry.

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Sleepy_C OP t1_j2096yz wrote

Is a hammer drill the same thing as an impact drill? My nearby tool rental place has impact & rotary drills, but nothing called a hammer drill specifically.

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BigDan1190 t1_j20a9eu wrote

For concrete you want an SDS drill, try that term instead.

Edit: also watch some videos on YouTube on the difference between different types of drills and how to drill walls without hitting anything such as pipes and electric cables.

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Intelligent_Ebb4887 t1_j209r0i wrote

No, hammer drills are different. If you have a harbor freight, their cheapest one is about $35. You'll probably need additional masonry bits as well.

When using the masonry bit, dip the tip in water every 1-2 minutes, it will keep the bit from getting too hot and wearing out as fast.

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Sleepy_C OP t1_j20ac3k wrote

Okay awesome, I'll go in and ask in person then and see what they've got. Thanks the advice!

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puterfixer t1_j20nedp wrote

There are a few technologies for hammer drills. Generally you have a selector button on the side if you want just drilling or also with hammer function, or in some cases just hammer (bit doesn't rotate, useful for chisel-like bits).

One simpler technology does the hammering through a couple discs with a Z profile - the rotation of the motor plus your force of pushing the drill towards the wall gives the bit some light hits. These make a lot of noise and not too much progress in hard concrete, and your arms will go numb. I don't think I have ever seen one advertise the impact force or, if it did, it was rarely above 1J (Joule).

Then there's the other kind, which generates the impact force either mechanically or pneumatically. They are generally bulkier and seem to have a secondary motor perpendicular to the drilling axis. These go easily into 2,5-3J. They are not so loud, but VERY efficient. Just be careful at first, the drill will feel like it's pushing you back a few inches ehen it reaches the concrete layer, hold steady so that you don't break it. The SDS mandrel helps (instead of the classical drill bits).

Borrow or rent one for a few holes. If you need one more frequently or want to own one, look for Lidl's promotional periods when theybput on sale their Parktool model, it is excellent for its price without breaking after the 5th use.

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Sleepy_C OP t1_j21awp0 wrote

Awesome summary thanks. It's definitely for just these four holes so I'll opt to rent. But that's super helpful.

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cieg t1_j21hn8n wrote

You can use an impact with a masonry bit.

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Intelligent_Ebb4887 t1_j21qekf wrote

You could also use a regular drill. It's just not as effective.

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cieg t1_j23h0ml wrote

I’m in construction and especially for small projects like this an impact works great. If there’s a neighbor or friend with an impact they can borrow to drill four holes in brick or concrete it doesn’t take but a few minutes to do. If you need to drill hundreds of holes, definitely go buy a quality hammer drill or root hammer. Depending on the hardness of concrete, or if there’s rebar involved, yes, you should get the heavier duty drill.

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GrimResistance t1_j246woi wrote

For anything up to maybe a 3/16" bolt I wouldn't bother buying a hammer drill if you've already got a regular drill.

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Intelligent_Ebb4887 t1_j252zks wrote

The TV mount that I just installed on a brick wall required 3/8" holes for the anchors.

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TheYoung_Wolfman t1_j20klv0 wrote

Hammer Drills are also called Rotary Drills, Rotary Hammers, or SDS Drills. If you plan on staying at this house for awhile, I'd invest in a cheap hammer drill to keep on hand.

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tminus7700 t1_j23512v wrote

Yes. I have found that you can drill into a rock in the cement. The rock is often much, much harder than the cement. And that will greatly slow down a typical carbide drill without hammering.

Also be very sure the wall is not pre-stressed concrete. If it is you can severly compromise the structural strength. My daughter bought a fairly new house in Las Vegas. The garage floor is pre-stressed concrete and has a warning molded into the front main florr near the door that says to not cut or drill into it.

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Chairmaker00100 t1_j20b7pl wrote

If it is actual concrete it could be tricky with a standard hammer drill. SDS drills tend to have a bit more oomph , I would recommend one

Edit: remember to use a masonry drill bit whatever type of hammer drill you use

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Sleepy_C OP t1_j20bvs6 wrote

Awesome, thanks. Everyone seems to be agreeing that a hammer or SDS drill is the way to go. I'll drop into my local tool rental place and ask tomorrow what they've got for the job.

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JTSkittrell t1_j21g3nd wrote

It's definitely sds and not just a hammer drill you'll want, I'd suggest trying it out on a pit of waste masonry if possible first, it's not like a normal drill it punches into the surface you are drilling

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southernliberal t1_j2092po wrote

The blocks may be filled with concrete, which is harder than blocks. If you are really unlucky you may have hit a piece of rebar. Try a new bit or move over and try a new hole.

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O_to_the_o t1_j208r45 wrote

When drilling concrete you want a hammer drill

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twohedwlf t1_j208srw wrote

First, you need a hammer drill and masonry bit. Sounds like you may not have them?

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Turbogato t1_j209hf3 wrote

Rent a Hilti Roto hammer or any hammer drill that has a handle attachment. Should make a bit easier leveraging yourself as you drill

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O-hmmm t1_j20gtti wrote

Something I have done instead of mounting the tv mount into cement was to build a frame the width needed for the mount out of 2 by 4's that went from the floor to the ceiling. I fastened the 2 by 4's to the floor joints above and the bottom just rested on the basement floor. You can box it in and it will cover up all the wires.

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jjammeh t1_j20jg04 wrote

You may find /diyuk useful for this and further more UK specific queries…

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dynamic_caste t1_j23dzn8 wrote

I got nerve damage in my hand from drilling a concrete floor with a hammer drill. It took months to heal. The next time I had to drill concrete, I got a rotary hammer. The job was so much faster and easier and no nerve damage.

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Metal_Monkey42 t1_j20dqhc wrote

Hammer drill for masonry bits, preferably of the actual hammer variety and not the crappy clutch hammers found in cheapy drill "with hammer switch action" drills. An actual hammer drill and a good bit will eat that wall like butter. Don't wave the bit around either, you want that hole to fit the spaghetti plug as tight as it can fit to get a good mount for a TV. And make sure the screws are long enough to go as far back as they can without bottoming out too early.

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JonJackjon t1_j20re0i wrote

Ideally a hammer drill or similar it the best tool. However if you have patience you can use a diamond core drill bit. Be sure it is rated for dry use (as opposed to water cooled, by hose or similar)

Something like this.

I would also consider getting a piece of plywood 3/4 or similar. Mount the TV on the plywood and use the cement plugs to hold the plywood. You can then put a number of plugs to hold the plywood.

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