Drill 10mm hole through external wall at an angle

[vemyr]

Hi, I want to drill an 10mm hole for coaxial through an exterior wall at an angle. It's a 1920s house and has 2 layers of brick with a gap in between, how can I do it at an angle without ruining the bit? Should both layers of brick be aligned so that if I go through mortar at the edge of the brick, it'll probably hit mortar in the second layer?

Cheers

 

[jeds]

Go for the bed joint. The bed joints might line up but it's unlikely the perp joints will.

 

[vemyr]

I'm drilling it at a ~20 degree angle upwards from the exterior so the bend diameter is big enough to prevent noise/damage on the coaxial cable. I'd start scraping the first brick a few cm in at this angle

 

[maltaron]

I do not understand how you will ruin the bit. You can get a masonry drill long enough to go right through the wall at whatever angle you need. An alternative would be a masonry drill with extension pieces which screw on. In either case SDS bits will be far superior to ordinary masonry drills, If you do not have an SDS drill it may be worth hiring one for a day.

 

[noseall]

I would be tempted to tape a bit of string onto the bit before withdrawing it through the masonry, to be used as a draw string later on.

10mm is not a very big hole when going through two leaves of masonry and a cavity and at an angle.

 

[cajar]

You have no chance of predicting where it will exit so ease the pressure the last few cm's to try for a nice clean exit hole. To get the angle just lift the drill slightly once it's started the hole, the bit can take it. The string on the bit suggestion is a good idea, although we use superrods. Don't forget to dress the cable into a drip loop or you will get water running down the cable and into the hole.

 

[Blagard]

I often use a small (6mm) bit to put a hole through first if I need a clean hole both sides. So long as you as ease off before going all the way through the break out is minimal. Then you can drill from both sides with the 10mm which leaves it clean both sides.

A bit of tape on the 6mm drill bit will usually be all you need to warn you when you can expect to break through so go easy on the last 15- 20 mm

A bit of maths will tell you that at 20 degrees through a wall 250mm thick the inner hole will exit 92mm higher than the outside and the hole will be 266mm long. You can vary those dimensions by simple proportions if your wall is different or use the web calculator like I did
http://www.mathopenref.com/trigtangent.html

 

[cajar]

It's an external wall with a cavity though, so more like 400mm, don't think you can get a 6mm bit that long.

 

[vemyr]

Thanks for the replies I'll see if I can find one of those bits.

 

[Blagard]

It's an external wall with a cavity though, so more like 400mm, don't think you can get a 6mm bit that long.

Try even 600m long

http://www.ccw-tools.com/product.asp?P_ID=30408

And a bit shorter at 450mm

http://www.thanettoolsupplies.co.uk/product/586/alpen-6mm-x-450mm-o-a-sds-plus-masonry-drill-bit

Anyhow how do you get to 400mm cavity wall. Early Cavity walls are 102 brick. 50 cavity and 100 inner leaf with plaster, say 12mm. so far up to 262mm!

 

[cajar]

I use a 400mm for external walls because some walls are rendered and have sand/cement render + plaster or studwork inside. Sometimes I need 600mm if they are blocks or have that polystyrene insulation and render on the outside. In the case of a normal cavity wall, I accept your measurements though. I wouldn't put much faith in the first bit you linked at £3 though, looks like it wouldn't break through yesterdays wheatabix!

 

[Blagard]

I use a 400mm for external walls because some walls are rendered and have sand/cement render + plaster or studwork inside. Sometimes I need 600mm if they are blocks or have that polystyrene insulation and render on the outside. In the case of a normal cavity wall, I accept your measurements though. I wouldn't put much faith in the first bit you linked at £3 though, looks like it wouldn't break through yesterdays wheatabix!

To quote one of the sellers:
Using a really long bit "it is advisable to always pre-drill the hole using a 160mm o/a length bit first. This will then eliminate any excess whip that long drill bits have, thus avoiding drill bit breakage."

I use a 400mm long one which is more readily available. I don't bother with a shorter one when I use it.

 

[cajar]

Yeah I read that advice and thought I'd try it, cos my 600mm ones always start going a bit warped before they blunt.