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Carpentry & Joinery

Cutting large neat hole in floor


I'm having radiators removed on ground floor and a forced air system installed soon. The diffusers have arrived and they are circular floor mounted types. Being round I have much better choice locating them in the bays than oblong types, which would interfere with the joists.

However the holes will be cut through original boards in one room and boards + strip maple in the other. Getting the centre between joists should be straightforward enough, but how do I cut a really accurate 211mm hole? There is only a few mm to play with as the edges of the diffuser unit are only that much wider than the part that is inserted into the floor...

I've seen ring drills up to maybe 80-90mm but is there something simple for a perfect hole this size? Other than that it's drilling small holes and sawing/filing. Anybody?


I like the look of the Starett Holesaw; 210mm would be all but perfect. But £130 each - tp cut 4 holes... this project is already way over my original budget! It would be handy if they could be hired, mind... :)


2 Answers from MyBuilder Carpenters & Joiners

I think you are stuck with a fine cut jig saw blade. You will need a good quality
jig sa handled with care. Start with some 1mm holes to get blade in .
Sounds like you have a cost dilemma, but good result with the starett holesaw.


Answered 27th Jan 2013

Simple, just use a 210mm starrett holesaw. Perfect results everytime, no filing, just neat perfect holes. See link below for more information.

Can be bought much cheaper on ebay! - see link below;


Answered 17th Feb 2013

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