Re: best way to make "great" retangular holes on concrete walls?

If it was me I'd get a masonry diamond blade for the angle grinder. I'll scribe the rectangular hole then cut the lines using the angle grinder as deep as I can using the diamond blade. I'll then load the rotary hammer drill with a bit long enough to exit the wall. I'd drill holes first to make it easier to break the masonry. If the hammer drill has a chisel function I'd load it with a Bosch Viper chisel and if not I'd just use a big hammer and manual chisels for the perimeters.

If any rebars are encountered then I'll use the angle grinder with a cutting disk to cut these out.

Re: best way to make "great" retangular holes on concrete walls?

Hi there bro narmenia,

I've done this several times when I was renovating my dirty kitchen, well not for aircon installations but for additional window steel casement installations. My procedure was similar to what JayL has mentioned but with some differences also.

What I did was to measure the dimension of the steel casement, then make a layout line on the wall with a larger measurement after which I got my 7" angle grinder fitted with a diamond cutting disc and start running and cutting the concrete on the outlines all around on both sides of the wall. Now after making deep cuts all over the outlines on both sides of the wall, got my Maxsell Rotary hammer fitted with the pointed chiseling bit, would start boring and making holes along the lines thru and thru, as many as I can all around, after doing so would again get my 7" angle grinder and would start cutting the concrete in the middle, sort of making some grid, cutting horizontally, vertically and diagonally, purpose of this is to weaken the hold of the concrete and would be easier for me to use a sledge hammer little by little bringing down the unwanted part of the concrete wall.

Kaya lang in doing this procedure, be ready with lots of basahan and a pail of water, walis tambo or a vacuum cleaner and dust pan, why ? because it will be very dusty and messy everywhere.

Hope this helps !!! :p :thumbup: :loopy: