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

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?

"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?

On Sat, 18 Jun 2011 14:31:59 +0100, Bert Coules wrote:

In the past, drilling holes through the wall has always resulted in the
inner surface breaking away, sometimes quite extensively,

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.

--
Cheers
Dave.

Dave Liquorice wrote:

On Sat, 18 Jun 2011 14:31:59 +0100, Bert Coules wrote:

In the past, drilling holes through the wall has always resulted in
the inner surface breaking away, sometimes quite extensively,

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.

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

--
Paul - xxx

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

On 18/06/2011 14:31, Bert Coules wrote:
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


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.

--
Dave - The Medway Handyman www.medwayhandyman.co.uk

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

Bert Coules wrote:
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




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