I have a hole about 15mm diameter going through about 1m of stone wall. It's for audio/network wiring and I now need to put through more cables than will fit.
I'd like to expand the hole and ideally line it with some 32mm waste pipe. So I need a roughly 35mm hole with a strong preference for it being exactly along the line of the existing hole.
I've heard that core drills are great for this sort of thing but I've never used one.
I have a cheap SDS drill. What more do I need? Can the core drill be guided along the existing hole? Do I buy cheap stuff or hire good stuff? (I'm unlikely to be doing much like this in future.)