Pete wrote:

Does anyone know of a good way to cut a 7.25 inch (185 mm) circular
hole through a wall?

I have attempted to hire a hole cutter but they seem to stop at 6",
which is definitely too small.

The depth and nature of the wall is an additional problem. It is about
12" thick, and is made up of two 4" rows of breeze blocks with an
insulation-filled cavity between them. The breeze blocks are faced with
masonry on the outer wall, and plaster on the inner wall.

Last time I needed to do something like this I stuck a 10mm hole right
through the wall and used it as a center to mark a suitable circle on
each side. Chain drilled round the edge, and then joined the dots with a
20mm chisel in the SDS. Once the pipe was in place and a bit of mortar
around it looked plenty neat enough.

--
Cheers,

John.

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