Enlarge hole in window recess

[Raskus]

I was thinking of changing the spotlights in my window niches, the holes are 60 mm now and would need to be enlarged to 72 mm.
Does anyone have tips on a successful approach?
There are 10 holes involved, so it needs to be fairly time-efficient, tips like a round file are out of the question.
A hole saw would be good, but there's nothing directly to drill into.

 

[huggan]

Screw a new piece of wood or sheet over the hole and drill a new hole. Then just fill the screw holes afterwards.

 

[thomas33]

If you cut out a 60mm hole in a thicker plate, you should be able to use the cut-out piece to guide the 72mm drill.

 

[Raskus]

If you cut out a 60mm hole in a thicker plate, it should be possible to use the cut-out piece to guide the 72mm drill.

That was a good idea, maybe they could be attached together with hot glue or the like to get better guidance.

 

[Matti_75]

Check out Pro-fit hole saws, with them you can connect a 60mm for the guide and a 72mm for the new hole.

 

[verktygsgurun]

Also says profit. Just connect two hole saws and go.