HARD concrete

[Sidney Endon-Lee]

Minor D-I-Y jobs that according to others "should just take you five minutes" have a tendency to turn into sagas.

Drill four holes in the wall to put up a hat rack.

Said wall is concrete. HARD concrete. 850 watt SDS drill borrowed for the purpose with new bit makes pretty much zero impression, and wnaders all over the shop. Ordinary hammer drill with bullet tip drill bit does the job eventually, after drilling small (4 mm) guide hole with standard masonry tip. Each hole probably took 20-30 minutes of drilling, which won't have endeared me to the neighbours.

Had to drill eight holes to put up cupboards a couple of months ago: Battery powered SDS borrowed for the job ran out of puff after a hole and a half, so borrowed a BIG DeWalt SDS which did those holes like the wall were butter. Unfortunately, couldn't borrow it again (lender was away on hols), so tried to use a standard SDS - which made no impression. Given the battery powered one worked while it had charge, how come the standard wired one didn't?

What on earth was this concrete made of?

(Oh, and minor rant: woodscrews that snap half way into the job, leaving me the job of taking the pieces apart held together by a now headless screw, so I can replace the screw. Screwdriver bits made of butter. This weekend was not a good weekend).

[tony sayer]

In article , Sidney Endon-Lee scribeth thus

Advice.. Invest in a good SDS drill you won't look back in anger..

Haven't met any concrete that my Makita can't handle as yet;))..

Buy better quality ones then;!...

[dom]

There must be something unusual about your concrete, or some of these drills/drill-bits are particularly naff.

IME my bosch, with even a quite worn bit, will put a 20mm bit into concrete where flint has been used as aggregate.

What do you know about the concrete, age? composition? used for some special purpose? (e.g. your house is a converted nuclear bunker)

Brands of drill/drill-bit that were good/bad?

[JimK]

was it shagged? either the hammer mechanism or the chuck could have been "well used"/abused by previous users - levering whilst chiselling shags chucks, no grease on the bits means the mechanisms wear quicker etc etc

Even a cheapo new SDS is worth your while - my =A330 jobby still does the (occasional) business :>)

A mate bought a Dewalt small SDS drill - I couldn't believe it could claim to be SDS ... it was sh1te...about the only thing SDS about it was the chuck!

Cheers JimK

[dom]

I saw those heavily discounted at Interbuild last year, nicely compact for awkward access (but my rule is not to buy unless I have an immediate use).

I'm glad I didn't!

[Sidney Endon-Lee]

Concrete is around 25 years old. No idea about composition, other than it appears quite fine grained, and it's HARD. I don't live in a nuclear bunker. The particular wall I was drilling into was around the stairwell/ communal entrance hall - it's a 5 storey block of flats.

Drill bits: Black & Decker Piranha 6mm diameter SDS-Plus (New) Unknown brand 6mm SDS bit, supplied with borrowed drill - (Used) - Useless. Black & Decker Piranha 6mm "Hi Tech" Bullet (Lightly used until now. :-) Black & Decker Masonry 4mm Bullet "Pilot Point" (New)

The SDS got nowhere. Well, not completely true, 10 minutes drilling gave me about 5 mm depth into the concrete, but no further. The drill (not mine) is probably not working properly, I guess. Hammer drill with the 6mm bullet tip worked slowly. One hole was difficult, as the SDS had wandered. I finally succeeded by drilling a pilot with a 4 mm masonry, then enlarging with the 6mm hammer drill.

I will need to drill some more holes. I'm reluctant to buy a random SDS if it isn't guaranteed to perform.

[Sidney Endon-Lee]

It shows price is no indication of quality. They were not cheap - local 'shed' rip-off. I've half a mind to complain, as this is not the first to lose it's head. But it's a learning experience: moral is, use pilot holes when it is important.

Cheers,

Sid

[Bruce]

It's all to do with the choice of coarse aggregate.

Concrete is made up of cement paste (cement and water) which coats the aggregate and glues it all together. The cement paste itself isn't particularly strong. The strength comes from the coarse aggregate and how it interlocks within itself, with the gaps between pieces of coarse aggregate filled by fine aggregate (sand) and cement paste.

That's how concrete works - the combination of the strength of the aggregate and its ability to interlock gives concrete its overall strength; the cement paste is a weaker link that holds it all together.

The hardness of the coarse aggregate in your concrete is probably what is making the job so difficult.

[Dave Liquorice]

Agreed, possibly technique as well. You don't lean on an SDS drill like you do a hammer drill, apply pressure but let the drill do the work and remember to pull back to clear the dust from the hole. SDS bits have more metal in 'em than a masonary drill so less room for the dust.

I've put a 20mm dia hole through 12"+ of stone with my Bosch rotating the wrong way, I did wonder why it seemed to be making harder work of it than normal.

[Sidney Endon-Lee]

Thanks Dave (and thanks for the confession). I did all that - if I let the drill do the work, nothing happened. Relatively firm pressure gave _very_ slow progress. It leads me to the conclusion that the drill is worn out (which the owner won't like) - it's possible the owner abused it in some way.

The drill bits could be naff as well.

I would not be surprised if the aggregate is granite.

[Dave Osborne]

I'm not so sure that there's any such thing as naff SDS drill bits.

They don't have a sharp edge and the tip geometry isn't important, so, as long as the SDS-end fits the drill properly and the tungsten carbide tips don't fall out of the business end, then it's all good.

SDS drills essentially work as a hammer-and-chisel, rather than cutting or scraping a hole, so what's important is the energy of the impact on the SDS-end of the drill bit.

It sounds to me like the drill is shagged or not man enough for the job. Given that you mamaged to drill the holes with a hammer drill, I would think that the SDS is shagged.

[Sidney Endon-Lee]

Maybe I should go low-tech and see if I can find a Rawl drill :-)

[dom]

I've done that briefly with a chisel bit/roto-stop - I wondered why the hammer action had got so weedy - is the drill shagged? is there a bad connection?

I both our defenses - the direction switch is a swing paddle rather than a push-push and is easy to dislodge.

[Andy Dingley]

How did you keep it in the hole? The couple of times I've done this (very light finger-tip switch to reverse my AEG) the tip of the drill bit drills just as happily, but as soon as there's any dust in the hole, the flutes turn into a woodscrew and wind the drill back out of the hole at me.

[js.b1]

Try a fresh Dewalt SDS bit.

- If it drills poor, your hammer action is damaged.

- Without sufficient hammer energy the bit is left to spin and overheat on hard aggregate. The now destroyed bit will just wander around, everything becomes noise without progress.

Try a fresh Bosch Multiconstruction bit, hammer off.

- If it drills fast your hammer action is damaged.

- This used to be common with old cheap wornout non-SDS hammer drills. Eventually you would find drilling soft facing brick was like hard engineering brick, all noise and no progress. So you changed the drill bit and found no difference, blaming it on the brick. By chance you switch off hammer and stick a Bosch Multiconstruction bit in and away it went - bingo, hammer action stuffed.

There are two cheap kinds of SDS, those heavy as a tank which seem ok and those that "just have an SDS chuck" on a 1980s body.

[Dave Plowman (News)]

Are you absolutely sure it is an SDS drill? If so, it's broken.

[Dave Plowman (News)]

Something must have changed, then. I've got the original small DeWalt SDS drill which is many years old now and despite a fair amount of DIY use still performs as new. One of my best buys ever.

[Sidney Endon-Lee]

As sure as I can be.

It's one of these:

Einhell Limited Edition LE-BH 826

more details here:

It's certainly SDS as it uses SDS-Plus bits. The instructions are here:

's not mine - it's a (foreign) neighbours. I'm unsurprised to learn it weighs 5.3 Kg. I've never heard of Einhell before.

Cheers,

Sid

[The Medway Handyman]

Thats a point. Is the OP sure its going the right way?

[The Medway Handyman]

Nor have I. Concrete and also some turbo nutter engineering bricks on Army built houses have never bovvered mine..