Cutting through concrete can be challenging when you are installing vents and piping around the home. For small holes, one of the best tools is a cold chisel, which is simply a hand-held, non-electric chisel. Although cold chisels take longer and require more effort than pneumatic chisels, they allow for more precise cuts. In addition, cold chisels are less cumbersome to use on vertical surfaces than the heavier electric models.
Use a pencil and a straight edge to draw the outline of the hole on the concrete surface. If you are creating a circular hole, insert the pencil into a compass and hold the centre post still to draw a perfectly round line.
Put on safety glasses and non-slip work gloves. Install a 1/4-inch diameter masonry drill bit in a hammer drill.
Place the tip of the drill bit on the pencil line and drill a 1-inch-deep hole in the concrete. Remove the drill bit and repeat the process to drill similar holes spaced at 3- to 4-inch intervals around the pencil line.
Pick up the cold chisel and place one corner of the blade on top of one of the drilled holes. Hit the top of the chisel firmly and repeatedly with a hammer until the concrete starts to chip away.
Reposition the chisel to another section of the pencil line and repeat the process to chip away more of the concrete. Work your way around the circle until you reach the starting point. Then start over and continue chiselling around the circle until you break through to the other side of the concrete.
Wait until you have an exposed hole in the concrete and then hit the centre of the pencil outline with the hammer to break the remainder of the concrete out of the hole.
You can purchase a plastic grip to insert on top of the chisel that helps you grasp it better. The grip also has a section that protects your hand from slips of the hammer.