I need to add an extractor fan to our utility room so I started drilling a hole using a core drill bit from the inside to outside. Its a standard UK brick cavity wall, so brick > insulation > brick. I got through the inner brick wall no problem, but when I started going through the outer wall, rather than cutting the brick I actually ended up pushing the brick out slightly.
After going outside to check, I realised the mortar had vibrated out while drilling, so I re-pointed up and left it a week to dry. Tried again, being quite light on the pressure and same thing happened again. I'm about a third of the way through the second row of bricks.
What can I do to stop these bricks pushing out while I'm drilling the bore hole for the extractor fan?