Whats the easiest way to drill a 4 inch hole thru double brick wall ??

Depends how hard the bricks are, and what access you have.

There's also:

I have used technique. Took about 2 hours. Cost - depends on what you have.

I used :- 1/2 inch 18 inch long TCT masonry bit (about a tenner), hammer drill, hammer, chisel, bucket and a ladder to put an extraction vent in for our ensuite upstairs.

Put a pilot hole through from inside to outside first, at the circle centre, so you can work from both sides.

You don't state the altitude of this hole. I certainly wouldn't want to use a core drill if standing on a ladder!

Unless it's essential to drill a very neat hole, the best bet is a ring of small holes, and then a chissel. As someone else has said, drill a pilot hole right through the middle first, then mark out your circle on both sides of the wall and drill the small holes from both sides.

It's best to use an SDS drill if you have access to one. It can also do the chisselling if it has a rotation stop. If you're careful you should end up with a reasonably neat hole - with any irregularities being covered up by the flange of an extractor flap or whatever.

Cheap but will take a while

It might

Depends on your hand drill. Something with 800W (ish) or more might manage if you take it easily. You really need something with a safety clutch though.

and if drilling from inside to ouside on hammer action watch out for surface spalling on breakthrough.

Jim A

The easiest is probably the wet diamond, but as with all things there one (ease of use) more than one factor at stake.

1. requires least kit, will have the scruffiest result.

1. is Noisiest, and likely dustiest, and the bits don't last more than few holes.
2. Will be by far the messiest.

Is noisy and requires the a mains drill with a