Extractor ducting hole!

Mark M

Mark M

Mark M

Soldato
Joined
6 Jan 2006
Posts
3,410
Location
Newcastle upon Tyne
Im fitting a new extractor and when Ive looked at the existing hole its been a half arsed attempt at chipping a bit of brick out so its going to need sorting as I need to put a 125mm or 150mm duct through it according to the manual although from what Ive read the bigger the better so will try for 150mm if possible.

What is the best way to tackle this? Its going through block and brick and I dont have any coring bits but happy to buy if thats the best way. I have some long drills for my SDS and wasnt sure if it will be easier to mark out the duct hole and then drill multiple small holes?

I have limited access from inside so ideally this needs to be done from outside. My SDS drill has a safety clutch but it will be up a set of ladders as its about 8ft from the ground which I know isnt ideal hence me wondering if the multi-hole option is better?

Thanks.
 
Buy a core drill bit, multiple holes is a bodge. 8ft isn't very high, you could fashion some sort of platform to work at that height if not comfortable on ladder.
 
I did mine recently to 125mm and used a coring bit. Took about 6 minutes. I reckon it would have took absolutely ages with multiple holes.
 
I did 125mm core hole for extractor fan last summer same height took me 20mins as it older house with hard bricks . I did about 98% from outside then then last 2cm from inside thru the plaster with plastic sheets all over me and drill ;)
 
200sols said:
Buy a core drill bit, multiple holes is a bodge. 8ft isn't very high, you could fashion some sort of platform to work at that height if not comfortable on ladder.
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Thanks, I could try and see if my hop up gives me enough height actually.

dLockers said:
I did mine recently to 125mm and used a coring bit. Took about 6 minutes. I reckon it would have took absolutely ages with multiple holes.
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Ok core bit it is! Will the Erbauer Diamond ones be ok for one hole? Do I also need the arbor to get it to attach to the drill or will I need the extension adapter too as Im hoping to do it from the outside?

So may questions sorry!
 
hotdog said:
Cannot overstress how important bigger is better for extraction!

Money well spent, do it once, do it right !
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I wondered why the old one was complete rubbish, assumed it was just a duff extractor but the hole in the wall is about the size of a tennis ball and the duct is just pushed up against the wall so half of it just vents out into the ceiling void I presumme!
 
You'll need the arbor with the erbauer yes. You'll probably need the extension to go all the way through from one side but beware forcing it through and blowing the inside wall.

For a single hole a cheapo core bit like linked above will also be (usually) OK.
 
200sols said:
You'll need the arbor with the erbauer yes. You'll probably need the extension to go all the way through from one side but beware forcing it through and blowing the inside wall.
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Thanks, I'll pick up both just to be safe. I can measure the depth from the existing smaller hole so I can set the guide on the drill to let me know when Im getting close and I'll make sure I take it easy from there.
 
Is there a reason you need to drill inside out? Sols shared a trick about putting a board over the exist hole to stop the drill jumping around.
 
You can't use a core drill to enlarge an existing hole.You need to fill the hole in first so you have a guide for the drill.
You are better using a proper core drill if you are doing to go for 150mm. Just rent it.
Be aware that eight feet in the air is pretty dangerous with a 150mm bit. Full of brick the bits become very heavy and its dead easy to lose control of them.
 
dLockers said:
Is there a reason you need to drill inside out? Sols shared a trick about putting a board over the exist hole to stop the drill jumping around.
Click to expand...

The extractor duct goes up into the ceilng void and then out so I cant get the drill in from the insdide and the ceilings have been plastered now! Big oversight somewhere between me, the builder and the kitchen fitter but it is what it is and needs sorted, ideally from the outside if possible...

pp111 said:
You can't use a core drill to enlarge an existing hole.You need to fill the hole in first so you have a guide for the drill.
You are better using a proper core drill if you are doing to go for 150mm. Just rent it.
Be aware that eight feet in the air is pretty dangerous with a 150mm bit. Full of brick the bits become very heavy and its dead easy to lose control of them.
Click to expand...

Oh, thats not ideal as I have no access now to the internal blockwork. I could, in theory, replace the external bricks but I wouldnt have a clue where to start and the builder is no longer on site.
 
pp111 said:
You can't use a core drill to enlarge an existing hole.You need to fill the hole in first so you have a guide for the drill.
Click to expand...

You can. You just need to fix a guide to the wall first. Plywood cut out hole size, fix over existing hole and drill. Its very easy actually.
 
200sols said:
You can. You just need to fix a guide to the wall first. Plywood cut out hole size, fix over existing hole and drill. Its very easy actually.
Click to expand...

Just watched a video on Youtube which used this method so seems doable thanks.
 
The guy who did ours had a huge core bit with a massive ancient drill. He said he had had it for years and it had never let him down and was better than the majority of drills you can buy these days. He was drilling away making a hell of racket when we heard a outburst of cursing, many of which I never knew existed. It turned out that the core bit jammed and the torque from the drill nearly broke his wrist. I have done that in 14mm steel with a lesser drill than he had and it bloody hurt lots!!
 
pastymuncher said:
The guy who did ours had a huge core bit with a massive ancient drill. He said he had had it for years and it had never let him down and was better than the majority of drills you can buy these days. He was drilling away making a hell of racket when we heard a outburst of cursing, many of which I never knew existed. It turned out that the core bit jammed and the torque from the drill nearly broke his wrist. I have done that in 14mm steel with a lesser drill than he had and it bloody hurt lots!!
Click to expand...
That's why you NEED to use a drill with a clutch. When I did a hole for a 125 duct it caught once, glad for the clutch.
Took me ages through a cavity wall of engineering brick. Luckily we were having a new roof so I had scaffolding I could use.
 
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