On 17/11/2016 19:45, Andrew Mawson wrote:
OK chaps - suggestions please.

I need to cut a 12" diameter hole in a workshop wall construction of
which is a single skin of 9" x 18" x 4.5" 7 newton concrete blocks. Now
I've all sorts of drills, angle grinders, hammers and even demolition
breakers, so the problem isn't removing the material, the problem is
doing it without the wall collapsing !!!

12" is really not a large hole - old boiler flues were frequently as
large as this.

Stitch drill and break out the middle with a SDS would be one approach.

If you want a neater round hole, overlapping core drilling also works.

You may be able to hire core kit large enough to do it as a single core.

Alternatively just chisel out the mortar and remove hole blocks, then
fill in round your exist pipe with new mortar and bricks (or bits of)


There are also firms that specialise in this kind of thing. A local one
here for example:

http://kssdiamonddrilling.co.uk/diamond-drilling/

(they claim they can do a 1.5m hole!)

(this is for a huge 3900 cuM/Hour extractor for a CNC plasma table down
draught exhaust)

Now this sounds like fun ;-)


--
Cheers,

John.

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