Best tool to enlarge a hole

danr86 · 16 Feb 2013

I've had some downlights fitted but to cut a long story short, they're the wrong ones.
As the ceiling is on a slope I need adjustable downlights, however the hole for them needs to be 85mm instead of the existing 72mm
What's the best way to enlarge the hole? Will I be able to use a hole saw as there won't be anything for the arbor bit to grip into in the middle?
Thanks

Untitled

danr86
16 Feb 2013
1

Cane32 · 16 Feb 2013

Your best bet is to mark 6.5mm with a pencil around the the circle giving you 85mm overall then cut it out with a pad saw job done.

xr4x4 · 16 Feb 2013

Or cut a plasterboard or wood template, hold this against the ceiling and drill through this.

DHFrames · 16 Feb 2013

Both ways will work, I'd opt for the mark round and cut out manually, not sure if 72mm + 6.5mm is 85mm though ???!!!

danr86 · 16 Feb 2013

6.5mm around will equal 13mm extra to the diameter so should be spot on

Mlacarpentry · 16 Feb 2013

Put the 72mm hole saw cutter inside the 85mm hole saw cutter so then you are using it as a guide there should be enough thread on the arbor to do it.

big-all · 17 Feb 2013

Mlacarpentry said:
Put the 72mm hole saw cutter inside the 85mm hole saw cutter so then you are using it as a guide there should be enough thread on the arbor to do it.

yes that will work but pad out the 72mm as much as possible with washers so it will be as far through the board as possible so the teeth are clear and the body will guide it through

catlad · 17 Feb 2013

Is this a new build?

danr86 · 17 Feb 2013

New extension on a old house...

catlad · 17 Feb 2013

I only ask because there can be condensation issues with those lights in a vaulted roof.

danr86 · 17 Feb 2013

Is that adjustable 240v in general?
Anything that can be done to avoid it?

pauldelahaye · 22 Feb 2013

If you have money to burn, Armeg make a tool for exactly this job!

http://www.armeg.com/AHC_Stabilizer-A00090.asp

Norcon · 22 Feb 2013

Pad saw will do the job but a good tradesman will just load the arbour with two holesaws. One guides and one cuts.
Most arbours will allow that.
Starrett make a vast range. 73mm and 86 available.
Not too shabby.

Edit.
OOh I see someone has suggested that. Silly me.

catlad · 23 Feb 2013

If you load up your roof with lots of lamps creating a lot of heat in a small space then when its cold you are likely to get condensation occurring. I do not know the solution, but I would buy LED's that give off the least amount of heat.

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Best tool to enlarge a hole

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