Core Drill C'ock up...

[christianbeccy]

I've drilled a hole through a 350mm cavity wall for a 6" extractor, using what I believed was the correct core drill (152x150).

Despite all the best will in the world, I've think I've managed to wander slightly, resulting in a hole that's not quite true. The result is that the 150mm liner I bought is REALLY tight and doesn't quite line up. I could do with a little bit of wiggle room. To put it in perspective, I've had the pipe 95% in, but it's pretty snug.

Any tips on techniques or tools I could use to fettle the aforementioned? I've tried the trusty hammer/chisel, but the inner skin is flettons and with no angle of attack, I'm bouncing off.

I'm thinking something like a drum sander or similar. I have considered going in there with an angle grinder, but I think it's a little dangerous given the tight space and potential carnage when it grabs. Might be the only option though?

 

[Tigercubrider]

cut a slit in the liner front to back

 

[Ian H]

Would the flap vent not cover the remaining 5%?

 

[christianbeccy]

cut a slit in the liner front to back

I'll consider this. I'd prefer to keep the liner intact, but this'll be a fall-back

Would the flap vent not cover the remaining 5%?

That's not the problem. I can't get the pipe to line up with the hole on the inside (basically the tile layer). Although the cutter passed through fine, the pipe won't. Therefore I can't get the fan into the pipe.

When I tap the insert in, it all stays true until the last 6" or so. It's frustratingly close, but just not enough.

Thanks for your input...

 

[oldbutnotdead]

Have you got the core drill still? If you have, make yourself a plywood (or chipboard or anything else similar) template (with a 150mm dia hole in it), fix the template to the outside wall (drill screw and plug) so the hole lines up perfectly with the hole in the inner wall then core away (using the ply to hold the core in the correct place) the bit of the wall causing you problems.

 

[John D v2.0]

the 152 core drill has an outside diameter of 152 (i.e. the hole size)
a 150 round duct has an inside diameter of 150 (and the outside is a couple more)
You would need to stitch drill or get an even bigger core drill to drill something adequately sized on the first attempt.

 

[tomfe]

You can make a 150mm duct fit a core cut 152mm hole but you have to be accurate/lucky.

Try using the core bit to rub against the point which the pipe binded. You could try putting the pipe in the freezer to make it smaller...

 

[Bilabong007]

If it's close could you not use carborundum to file it a bit?

There must be a way to file stone

Just a thought

Graeme

 

[Tigercubrider]

I'd think stick drilling with a small sds then either larger sds or a chisel would work.
Working from inside out to that the finished face is kept as good as possible

 

[christianbeccy]

Thanks for your help all. I'm going to have another look at it today, based on the recommendations above.