Stitch drill or Diamond Core drill?

[HomerSimpson]

I need to cut 4", 5" & 6" diameter extractor fan outlet holes in standard cavity walls. (inside = soft celcon, outside = fairly soft facing brick).
I was going to hire diamond core drills but the 3 sizes makes it quite expensive.

Has anyone had any experience of marking the circle and simply stitch drilling around the circumference and then knocking out with a chisel? Are there any problems with this apart from a ragged edge? (which I plan to fill and cover with a brown plastic extract grill)

 

[Sandy Beech]

Hi I have done this by drilling loads of holes then enlarging them before tackling them with a hammer and chisel but would now use at least a decent SDS drill with chisel bit in place of the hammer and chisel.

 

[noseall]

both systems work ok. diamond and stitch.

i have a 975/k kango which is a medium breaker and a large drill. it's an awesome weapon when armed with a diamond core bit. but not all masonry walls lend themselves well to the core drill method.

that's why an open mind an a good sds drill are essential. Bosch blue for me every time.

 

[^woody^]

Can't you standardise the fan size?

Or use one size core drill and fit a suitable (ie bigger) external vent cover to mask the hole if need be?