Extractor fan - core drilling 125 mm hole

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Hi There, looking for advice on how to drill a hole for extractor fan ducting - diameter is 125mm

OK, so I'm looking for advice on the right drill to buy + drill bit (I will be buying brand new) - I want a decent drill just for core drilling. By the way, will be drilling through stone and brick (the stone is very hard!). Plus any advice on how to use the drill

Also, to throw a further spanner in the works, there is already an existing hole of about 50mm diameter - so what would be the technique to make this hole bigger? (as there is no 'pilot' hole to help keep it in position).
 
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Money's not an issue for me and I like DIY - yes I know I can pay someone to do it but I want to do it myself and I want a core drill ;)
 
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Mark the circle of the new hole, use an sds and a good 6 or 8mm bit and stitch it.
Then use hammer and chisel to remove the excess.
Won't be as pretty as a core drilled hole, but cement/sealant/expanding foam along with collar will hide it.
 
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Mark the circle of the new hole, use an sds and a good 6 or 8mm bit and stitch it.
Then use hammer and chisel to remove the excess.
Won't be as pretty as a core drilled hole, but cement/sealant/expanding foam along with collar will hide it.
dammit I really wanted a new tool!
 
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He can with a bit of thought
The op doesn't own a drill, how much experience you think he has?
Wanna start telling him to cut a cylinder of wood, plug the hole, let dry, then core drill very gently until it grips, etc., etc.
A simple solution always works best and most diyer own an sds, so easier to borrow.
 
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Using a holesaw, cut the same size out of a 4" X 2", widen the hole in the centre and push it on the core guide rod, once inside the hole that will keep it centred.

another way is to use four screws and plugs just outside the new hole diameter, top, bottom and both sides as a guide,

or hold the core bit in the palm of your hand on a bit cardboard to get started and not be feckin about with holesaws and bits of wood, screws and plugs.
 
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All my bravado about money being no object has just been exposed! Might have been tempted at the £200 ish mark. I have a Milwaukee cordless drill though and they are awesome.. Milwaukee are usually well worth the premium price imo
 
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Core drills come in many disguises but are all expensive, they have a slipping clutch and dont work the same way as other drills
 

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