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McQueen777
Cutting a hole in Cement

So, I am trying to cut thru cement in my sidewall to install a new bathroom vent. I need to make a hole 4 inches in diameter in cement that is less than a 1/4" deep. Was hoping to get lucky with a hole saw on the drill, but to no avail. Any suggestions?

dj1
Re: Cutting a hole in Cement

You need a diamond boring blade for that, not hole saw (which works on wood).

Another idea, more practical if you need it for 1 time only and you don't want to buy it: use a grinder with masonry blade and carefully make small cuts until you get a round cut. If the cuts are too big, don't worry about it now, you'll fill them once your vent is in place. You can also hide them with a round flashing.

A. Spruce
Re: Cutting a hole in Cement

Another method is to draw your vent diameter on the wall, then using a masonry drill bit, perforate the perimeter of the circle, about every 1/8" - 1/4". Once the perimeter is perforated, use a masonry chisel and hammer to break out the bridges between the perforations, leaving you with the hole you're looking for without having to buy special tools and such.

Retroloco-LJ
Re: Cutting a hole in Cement
McQueen777 wrote:

So, I am trying to cut thru cement in my sidewall to install a new bathroom vent. I need to make a hole 4 inches in diameter in cement that is less than a 1/4" deep. Was hoping to get lucky with a hole saw on the drill, but to no avail. Any suggestions?

You can use a masonry drill bit. Draw a circle (4" in diameter) for where you would like the hole to be. Drill the center and a few inches from the center (1.5"-2") and so forth radiating from the center to the exterior circle you drew. You can then take a hammer and chisel and chip the cement away. If you need a clean hole then you'll have to finish the edges off nicely but the multiple holes within the area will weaken the cement so you can break it away easily.

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