I have to cut a 100×500 mm hole in a concrete slab that is about 80-100 mm thick. I think that I have two options to do that:
1) 9" angle grinder with segmented diamond disc: cut the long sides, then chip away the short sides with chisel.
2) Hammer drill with with a large bit making holes close to each other and the just breaking it out with a chisel.
Option 1 is faster, but is more expensive (I also have to buy the disc besides the tool rent) and it looks kind of scary after I saw some kick back results.
Option 2 is cheaper (bits come with the tool rent), but seems to be more time consuming.
Both options will leave a rough finish that will demand for stucco or something.
PS: I can access the slab from the top and the bottom if it matters anything.
Best Answer
The standard approach used by electricians routing large conduits through concrete floors is using a diamond edged hole saw cutting 3 or 4 inch holes. Several of these holes overlapping could do it. Or several holes near each other might suit your purpose. These drills need to be water cooled while drilling. You may be able to rent one.
Alternatively a smaller grinder could score the cutout on both sides, a drill could then break through the webbing left under the scoring and a chisel to finish it off.