Drilling concrete

[Bert Coules]

I'm about to drill (SDS drill, new 8mm masonry bit) into one of the concrete panels of my sectional garage. In the past, drilling holes through the wall has always resulted in the inner surface breaking away, sometimes quite extensively, but this time I'll be drilling down through the bottom of the panel and into the garage's concrete base (to fit securing bolts).

Is it safe to assume that because the underside of the panel is in close(ish) contact with the base, there's less risk of the concrete breaking?

Any hints for drilling this sort of material will be gratefully received. Many thanks,

Bert

[dom]

"Close-ish" is not good enough. A piece of wood in very firm, uniform contact with the far side might do the trick. Otherwise, is there any way you can accurately measure where your breakthrough point will be, and back drill any oversize hole?

[Dave Liquorice]

Function of an SDS when it break through if you are pushing the drill, think about how an SDS drill works... Once you get close to full depth stop pushing and take it easy, no gurantee that you won't get some spalling but it shoud be much reduced.

[Paul - xxx]

+1 or even change from an SDS to a normal drill, only using steady force.

[Bert Coules]

Thanks to everyone for the replies. I think that maybe I didn't make myself clear: the vertical panel is standing on the concrete base, and I'm intending to drill down through the panel and into the base. So in effect I'll have a straight-through hole (in the panel) and a blind hole (in the base). I'm hoping that because the base is up against the underside of the panel, it will prevent any spalling in the latter (and thanks to Paul for the correct term, which had eluded me).

I'm going to try it later this afternoon, so we'll see...

Bert

[The Medway Handyman]

Avoid going near edges for a start. If drilling through, get someone to firmly hold a large lump of timber over the breakout point, that cuts down the damage.

Try a wooden wedge driven in under the panel.

[Bert Coules]

Thanks Dave and everyone else who responded. I've done this now: the drilling went OK, and if there was any breakout under the panel it must at least have been contained with nowhere to go: there's no sign of any loose chips or other damage either inside or out, and the holes weren't impeded in any way.

The hardest part of the job was driving home the fixing bolts - Multi-Mondi hex heads from Screwfix. I had to use a small socket-and-ratchet tool and the last few turns needed quite an effort. Indeed, the last few turns on the first bolt proved impossible until I realised that I hadn't drilled the hole deep enough...

Bert

[F Murtz]

next time you could try drilling the smallest size possible then drill from both sides with the bigger drill.