You don't need Dimond Core drill for that. You can drill that Dia180mm hole with the Hammer Drill you already bought, just mark out the 180mm circle, then mark out a concentric Dia168mm (180-12) circle  and drill a series of dia 6mm holes on that 168mm circle so each hole has about 3mm gap, then use 12mm drill bit to enlarge each hole. then a little bit of hackingwitht he chisel bit to smooth out the 180mm hole shape and job is done.

The hole doesnt need to be super perfect since inside and outside should have a cover plate and a duct passing through the hole, right.

That's how about 90% of contractor would do it.

cheers

I didn't say it was the best way to do it, i said that's how about 90% of contractors do it.

It might take 1hr to do by hammer drill vs 30 mins by core drill, but you don't need to spend rm1k for core drill.

Also core drill not really easy to use on wall, its really best suited for boring through concrete floor.

No it cant , but I never said that.

There is a way to drill any size hole (160mm 180mm 200mm 350mm even) with standard Hammer Drill as given in my explanation of the method above, read that explanation and you should understand. Its not using hole saw or core drill bit, its using normal concrete drill bits and just dilling lots of holes that join together, a bit like perforations on paper.

Cheers