Large Diameter Masonry Hole Required - HELP!

[plasma boy]

Hi there

I am going to wall-mount a plasma screen telly above a fire place. The wall is a party wall in a terraced property, so will easily hold the weight (about 30kg). I am fine with fixing the coach bolts (probably about a 12mm bit required for the bracket fixings), but I am planning on sending the wires back into the wall and down the chimney (which is not used, obviously!) to avoid having to chase them into the wall. This will mean a roughly 50mm hole (to get the SCART plug through) in a brick wall about 200mm deep.

The question is: what type of drill bit do I need? Obviously a power drill is required, but I haven't made a hole this big before. Can you hire the bit? I will obviously only be using it once.

Any advice greatly appreciated.

 

[pitbull]

Drill a few holes in a circular shape then knock out with a hammer and cold chisel.

 

[oilman]

Hire a diamond core bit with extensions and a diamond drilling machine. Don't try using any other machine, the bits can bind VERY quickly. Do not force the cut, and have a vacuum cleaner set up to suck the dust away if you don't like clearing up the mess.

 

[plasma boy]

Thanks guys - I like the sound of the diamond core drill bit. That would be easier than the multiple holes and chisel I reckon. Why do I need a special drill though - I have access to a De Walt power driver. And what do you mean by the bit "binding"?

 

[gcol]

You ain't gonna need a perfectly round hole behind the TV, hiring a core drill is gonna cost you a bit too.
I agree with pitbul - chain drill a round hole and clear it out with the chisel.
You can always neaten the hole up with a bit of filler if you cock it up.

 

[Scrit]

Thanks guys - I like the sound of the diamond core drill bit. That would be easier than the multiple holes and chisel I reckon. Why do I need a special drill though - I have access to a De Walt power driver. And what do you mean by the bit "binding"?

Even a 4kg SDS can have problems of binding with a large diameter diamond core - and when the bit binds in the hole and the drill keeps going it can sprain, dislocate or even break your wrist in double-quick time........ Diamond core drills are also designed for high power output/torque and have thumping great metal gearboxes to handle the stress of drilling this way.

Scrit

 

[oilman]

You ain't gonna need a perfectly round hole behind the TV, hiring a core drill is gonna cost you a bit too.

True, but the plasma screen is such an expensive luxury, the cost of hiring the bit will be insignificant in comparison.

You can always neaten the hole up with a bit of filler if you cock it up.

As you almost certainly will.


When the bit binds and stops rotating, the drill goes the other way, your head is probably in the way. To get a similar effect, just hit your head with a 4kg SDS drill, you'll understand.

 

[2scoops0406]

Thanks guys - I like the sound of the diamond core drill bit. That would be easier than the multiple holes and chisel I reckon. Why do I need a special drill though - I have access to a De Walt power driver. And what do you mean by the bit "binding"?

Even a 4kg SDS can have problems of binding with a large diameter diamond core - and when the bit binds in the hole and the drill keeps going it can sprain, dislocate or even break your wrist in double-quick time........ Diamond core drills are also designed for high power output/torque and have thumping great metal gearboxes to handle the stress of drilling this way.

Scrit

And have safety clutches in order to stop you being rotated off the ladder that you foolishly climbed in order to drill out a core for an upstairs extractor (personal experience )

 

[oilman]

...............

And have safety clutches in order to stop you being rotated off the ladder that you foolishly climbed in order to drill out a core for an upstairs extractor (personal experience )

Now the sensible approach would be to do it from the inside and use a dust extractor

 

[2scoops0406]

...............

And have safety clutches in order to stop you being rotated off the ladder that you foolishly climbed in order to drill out a core for an upstairs extractor (personal experience )

Now the sensible approach would be to do it from the inside and use a dust extractor

Too deep, not possible.

 

[Diyisfun]

Plasma boy if you are in North London I may be able to help email me. (I work for a tool hire company).

 

[Scrit]

And have safety clutches in order to stop you being rotated off the ladder that you foolishly climbed in order to drill out a core for an upstairs extractor (personal experience )

Yeas missed the clutch bit...... I did however do the getting knocked off a ladder bit - ouch! Once bitten......

Scrit

 

[plasma boy]

Well I have found a tool hire place (in SW London near where I live) that will give me everything I need for about 35 quid. I don't think drilling through brick should be too much of a problem, as long as I take it slow, although I have taken on board your horror stories. I think I am going to go for it.

The multiple drilling technique sounds just a bit too fiddly to me - I don't see how I could keep all the holes parallel for 9-10 inches through the wall, so it would end up being an odd-shaped hole and need a lot of tidying up. Maybe ok for a 3-4 inch hole, but not in this case!

Thanks for your help so far - any further advice much appreciated.

Plasma Boy

 

[oilman]

................
Too deep, not possible.

I would have though the hole would be the same depth from the inside as from the outside.

 

[2scoops0406]

Well indeed, but I couldn't have got to the inside from the outside, if you get my drift.