On 01/11/2020 16:46, williamwright wrote:
On 01/11/2020 15:04, John Rumm wrote:
Well you could take a 12" square bit of 1/2" plywood, offer your 150
mm core bit up to it, and draw round. Now cut out the circle with a
jigsaw.

Stick some wide blue masking tape to the rear of the ply, all around
the outer square perimeter. Stick a matching square of tape to the
wall centred on your existing hole. Apply some superglue to the tape
on the ply. Spray some activator onto the tape on the wall. Now offer
the two together and press and hold for 15 secs. You should now have a
ring of ply stuck to the wall.

Use that you guide the core drill (no pilot bit required). once you
are 5mm into the surface, you can remove the guide by inserting a wide
flat bladed scraper behind the ply and prising it off the wall. (the
masking tape bond is very strong in shear, but not that strong in
tension)

Did you used to write manuals?

I have done so on occasion... and then a proper technical author would
usually come along, rip them to bits and put them back together properly :-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/