On 26/09/2019 14:45, The Natural Philosopher wrote:
On 26/09/2019 14:22, GB wrote:
I have a concealed cistern behind MDF, which has been tiled.

I am fitting a new flush valve in place of the old syphon. It's mostly
done, but I need to recess the button. That needs a 40mm hole through
the tiles and MDF, in place of the existing rather ragged 30-35mm hole.

What's the best way of doing that? 40mm drill will tend to wander. I
have a 1/2" belt sander, but that'll take ages. Any suggestions please?

https://www.permagrit.com/small-rotary-tools/

These willl take down tiles as well as MDF
(wear a mask)

Or

https://www.permagrit.com/radius-ext...e-file-coarse/

Permagrit tools are ruddy brilliant actually



Useful link, not come across permagrit. I was going to say that for
enlarging a ragged hole I'd probably use an abrasive tool in a Dremel or
similar, noting that the cheap ones that typically come with them are
often single use.