Enlarging 65mm Ceiling Downlighter Holes

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efunc

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Hi all, I need some advice on this dilemma. I currently have 65mm holes in my kitchen ceiling from my old halogen spots. I've removed these, wired LED GU10s instead and am looking for some new GU10 bezels to replace the old faded ones and the one's I've found that are small enough are quite ugly in my view, compared to more contemporary slim profile ones. The ones I'd prefer require a 75mm hole.

What's the best way of doing this neatly? I'd imagine using a 75mm hole cutter and trying to center it will result in a mess and damage to my newly decorated ceiling. I have 10 of these holes to enlarge, so am looking for a method that will be neat and easy to repeat.

Existing holes:

13-03-2021-16-31-08.jpg


13-03-2021-16-32-09.jpg


Replacement fittings, I'd prefer to 'replace':

13-03-2021-16-36-08.jpg
 
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Get a 1/2" thick scrap of wood. Drill out a 65mm hole and a 75mm hole in the wood. using the centre hole in the resulting round cut outs, centre the 65mm hole on the 75mm round and glue together. Then use the resulting template to fit the 65mm round into the existing 65mm hole and drill the 75mm holes out in the ceiling following the centre hole. Hope that make sense.
 
Bear with me, I'm going to have to read and re-read that several times!

Thanks though, intriguing!
 
Ah, OK, got it!

So, when the template is positioned over the hole in the ceiling, won't it spin out the moment I try to position my 75mm cutter over it? Also the 75mm saw would have to be quite deep wouldn't it to clear the wood template inside it? Otherwise, this sounds like something worth attempting. Thanks
 
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It might spin, an alternative is to fit a smaller hole saw (65mm) inside the larger one providing the arbour is long enough.

Blup
 
blup said:
It might spin, an alternative is to fit a smaller hole saw (65mm) inside the larger one providing the arbour is long enough.

Blup
Click to expand...

The 65 and 75 holesaws would probably be the same length, though I'm not sure spinning would be a problem, that could be remedied with some 3/4" panel pins knocked all the way in and protruding 1/4" out the other side of the 75mm disc.
 
Yes, but at that size you are into the arbor type with the extending pins (assuming you use a Starrett-type hole saw) so it should be possible to position thec65mm saw a few mlimetres ahead of the 75mm one and still get the pins to locate in both saws
 
A modified version of EddieM idea would be to fit a soft spring or some soft foam under the template inside the holesaw so it held the template ahead if the cutter until pressure was applied and then start slowly cutting.

IMG_20210314_083804269.jpg
 
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efunc said:
Very good. I like the DIY approach, on the other hand I've found these two arbours which allow you to fit two different holesaws at the same time, the smaller of which fits in the existing hole to anchor it:

https://www.amazon.co.uk/C-K-T3216-...02&hvtargid=pla-426064102972&psc=1&th=1&psc=1

https://www.lawson-his.co.uk/starre...22wDy_7asQ2qaEtQ-7XXHXibSiXcVTeRoC-38QAvD_BwE

However I then need to buy the correct size holesaws, which can get costly.
Click to expand...

Those adapters should be unnecessary, the arbour that came in my cheapy set was fine for fitting 2 cutters to.

Also got a cheap hole saw for the smaller of the holes, as it isn't going to cut anything anyway!
 
Pictures are deceiving but there doesn't look enough scope to mount the inner pilot cutter in advance of the outer one if that was your intention.
Edit: linked to in previous post
 
Last edited:
The sort of thing I was referring to was the Starrett-type hole saws which work with this type of arbor in the larger sizes:

Standard_Arbors_0.jpg


This is pretty much the standard industry arbor design for hole saws larger than about 32mm of the design used by Starrett, DW, Morse, Makita, Bosch, Milwaukee, Sandvik, etc, etc (in fact any half decent hole saw maker, as opposed to the DIY tool makers, even LIDL stuff sometimes features this sort of arbor and Toolstation do a knock-off for under a fiver - code 50147). The hole saw is spun onto the threaded portion of the arbor and locked in place by spinning the knob which extends the drive pins into two of the four holes at the top of the holesaw, hence the ability to get two saws on one arbor at the same time
 
Last edited by a moderator:
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