Minimising blowout when drilling through walls

I have a little cabling to do shortly that will mean drilling holes all the way through walls. I know that some blowout is probably inevitable, but does anyon have any tips for minimising it? Simply less weight on the drill and let it do it by itself? Small hole first then go both ways with the bigger one? turn hammer off when I think I am nearly through? don't worry about it, if it hppens it happens?

Reply to
Paul Matthews
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Yes, all of the above!

If you can drill from both sides of the wall that's obviously the optimum, but can be difficult/impossible to get them to meet in the middle (especially do-able with a cavity wall though).

If all else fails, I've had having a flat plate of thick plywood held really firmly against the wall where the bit was going to emerge*

David

*Actually, it was held in place by being braced by a length of 3x2 leant against the wall at 45 degrees, with the sylph-like SWBO perched on top to provide the necessary force!
Reply to
Lobster

Are you talking about an outside wall - brick on the outside, block and plaster on the inside? If so, try to drill from the outside if you can - for

2 reasons:
  • If plaster breaks out, you can repair it easily - but brick, you can't
  • You can choose exactly where the hole will be on the outside - and can go through mortar at a brick corner if desired [Make sure you know where the hole will be on the inside though, and check for pipes, power cables, etc.]

Something which I haven't tried, but which just might reduce breakout on a plaster wall is to wedge (or get an assistant to hold) a sacrificial piece of plasterboard against the wall, and to drill right through that - so that the drill doesn't immediately meet fresh air when it comes through the wall.

Reply to
Roger Mills

There is no complete solution which is guaranteed to work. If you can add some support at the back of the hole - piece of wood solidly braced against something, that is the most certain way to prevent it. It is the lack of support which causes the blow out. Another way is to drill the smallest size hole then be gentle for the last inch. then keep going up a size at a time and working from both sides of the hole.

Reply to
Harry Bloomfield

Drill as small a pilot hole as you have a drill for, going gently. Which probably means about 5mm. Then drill the required hole from both sides.

Reply to
Dave Plowman (News)

mark

Reply to
Mark

If its SDS a 5mm bit will only be around 160mm long. Probably have to go up to 10 or 12 mm.

Reply to
The Medway Handyman

Scrapwood on the far side, with a fair bit of force behind it. Be warned that old plaster may well lose adhesion and de-laminate anyway, it just won't visibly separate.

Pilot holes won't help in a brittle material like plaster. You'll see nearly as much delamination from the pilot as from the full-size hole.

Reply to
Andy Dingley

Yes - but small drills aren't too bad with an ordinary hammer drill on most internal walls. And I have a few 18" 5mm ones.

Reply to
Dave Plowman (News)

If you are using SDS then this a good one very little pressure will still get the hole drilled. Lean on an SDS and you are guranteed a saucer sized blow out. Mark the drill with a bit of tape as accurately as you can with the thickness of the wall. You can blast through most of the depth then ease of for the last inch and half or so.

That is a good method combined with the above ease off at the end. You will get a bit of blowout but the bigger drill latter may well remove all that.

Well there ain't much you can do so worrying after the event is pointless. One can do things before hand to reduce the chances of a big mess though.

Reply to
Dave Liquorice

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