Almost every major construction project involves cutting concrete in some way. Concrete is used for foundations and supports and cannot be modified after it has hardened without the use of proper power tools.
One of the many tools you can use to cut concrete is an angle grinder. You can use an angle grinder with a diamond blade to cut concrete and masonry. For heavy-duty deep cuts in concrete, you should use a masonry cut off saw.
Cutting Concrete with Angle Grinder
Before jumping into concrete cutting with an angle grinder, you will want to make sure you are set up for success. First and foremost, this includes proper safety measures. Utilizes gloves for hand protection and safety glasses for eye protection. Also, make sure your angle grinder has a functioning safety guard around the blade. If you are dry-cutting concrete, you will also need a face mask to limit your exposure to silica concrete dust.
What size angle grinder should you use for cutting concrete?
Angle grinders are meant for smaller, more detailed cuts in materials. That is why the standard size of an angle grinder is 4.5 inches in diameter. Keep in mind that while the diameter of the cutting disc is 4.5 inches, you will only get a cut about half of the distance, or 2.25 inches, minus the half of the clamping flange nut. The flange nut usually has an external diameter of 1- ½ inches. That means the cutting disc can only go around 1 inch deep into the concrete you are cutting.
How Deep Can an Angle Grinder Cut?
- 4 ½ angle grinder you can go approximately 1 to 1 ½ inch deep
- 9-inch angle grinder can cut to a depth of 3 to 3 ½ inches
It is certainly possible to cut through concrete up to 1-inch with a 4.5-inch angle grinder, but you might find the job gets completed quicker and with more precision with something larger like a 9-inch angle grinder.
The physical size of the angle grinder is not the only aspect to consider. The amps in the motor of the angle grinder determine how fast the grinder will cut. A 4.5-inch grinder will typically come with a 7 amp motor, while a 7 inch or 9-inch grinder will use around 13 amps. The nearly proportional amps mean each tool functions at about the same speed even though one is larger.
Which Cutting Discs are Best?
Cutting concrete with an angle grinder is always best done with a diamond saw blade. These blades are made from an engineered steel core with sharp, synthetic diamonds around the edge. Choosing a diamond blade for cutting concrete with an angle grinder is a no-brainer, but your options do not stop there.
You have a couple of options when it comes to the shape of the rim for a diamond cutting disc including:
- Segmented Blade: The separation in the toothed rim allows dust to rise out of the cut and airflow to enter which cools down the blade. This blade will give a rougher cut.
- Continuous Blade: For a better quality cut, a continuous rim blade is the best option. These discs are best used with wet cutting so the water will cool down the blade and remove excess dust.
Can you cut concrete with a metal blade?
It is possible to make small cuts on concrete with a metal disc, however, it does not perform quite like the diamond blade option. Metal blades are better for cutting and grinding metals. When used on concrete, metal discs will cut slower and overall be less effective.
You can get silicon-carbide wheels that cut through concrete and masonry. For the best results, I suggest you go for a diamond grit blade.
Once you have the proper tools and safety materials, it is important to know the exact techniques and maneuvers to get the most accurate and quick concrete cuts.
Cutting Concrete That Contains Rebar
Cutting through concrete that contains rebar can be a little more difficult than just concrete alone. If you are cutting a concrete slab or deck that is reinforced with steel rebars, a diamond cutting blade is still your best option. Be sure to use a new diamond blade as the steel will wear down the diamonds around the edge of the blade quicker than just concrete will.
Concrete with rebar cutting is not a job for amateurs. By design, concrete with rebar is very strong and can require extra force to be cut through. Be sure you measure where you are cutting and avoid any conduits or utilities that may be contained in the concrete.
Cutting Concrete Blocks or Slabs
Cutting concrete blocks or slabs without rebar in them is a bit easier of a task, but still requires proper planning. For concrete blocks, you will want to mark the location you want to cut and clamp the block down so you can make an accurate cut without the block moving.
For concrete slabs, you will have to make a series of cuts through the concrete. Once you have made a few inches deep cut, you will chisel or sledgehammer out the loose concrete you want to remove and then continue to cut into the slab until you have made it all the way through.
Cut concrete slab for gas line, drainage, etc.
Often inside home or garage interiors, you will need to cut existing concrete slabs beneath the flooring in order to install a new gas or drain lines. You can use an angle grinder to cut a recessed path in the existing concrete foundation just wide and deep enough for the piping to lay in.
It is important not to hit any other utilities that might be in the slab.
Using Water with Angle Grinder
For any of these concrete cutting techniques, you have the option to cut with a dry or wet process. Wet cutting allows for more precise cuts and is easier on the blade and the user. There are plenty of wet blade cutting adapter kits available for your angle grinder.
Dry cutting is often the preferred choice as it does not create the mess that using water does, however you have to compromise with the dust that this method will produce. Make sure you have the proper ventilation mask so you are not breathing in silica dust.
Keep in mind when purchasing your diamond blades, you can use blades made for dry cutting with or without water, but wet blades can only be used in wet applications.
- Cutting Concrete with Angle Grinder
- Cutting Techniques