How to Cut Flagstone With a Grinder

Flagstone makes an attractive paving material for a patio, walkway or wall in a garden or backyard. Part of its versatility comes from its flat, thin shape -- but although it's usually not thick, it can still be difficult to cut when you need smaller pieces to finish off a paved surface. Having the right tool is a must, and you need a grinder on hand when you're going to trim flagstone to size. But even with the proper tool, preparing the stone and following safety guidelines is key to successfully cutting flagstone.

Garden path with stone landscaping
credit: Elenathewise/iStock/Getty Images
Cutting flagstones means your path can have neat edges and tight joints.

Choose the Right Grinder

The most effective tool for cutting flagstone is an electric angle grinder. Angle grinders vary in size, but for most flagstone slabs, a 4- or 4 4/2-inch grinder is best. Choose a model with a motor that draws between 5 and 9 amps so it's powerful enough to cut through the stone. An angle grinder usually comes with different cutting wheels and accessories that you can attach depending on what you're cutting. For flagstone and other masonry, use a dry-cut diamond wheel on the grinder. Angle grinders can be expensive, so it might be better to rent one for a project.

Take Safety Precautions

Before you cut the flagstone, it's important to make sure you're safe. Cutting the stone creates a great deal of dust, so work outside where it's easier to clean up. Protect yourself from flying debris by wearing a dust mask and goggles. Wearing work gloves is also important because they can help you keep a firm grip on the grinder as you work, so you don't slip and risk an injury. Make sure that family, friends and pets aren't in the area of the grinder while you're cutting.

Prepare the Stone and Grinder

Getting the stone and grinder ready for cutting can make the task much easier. Don't turn on the angle grinder until you've marked the flagstone so you know precisely where to cut. Use a ruler, tape measure or other straight edge to mark a cut line on the stone -- you can draw the line with chalk, which shows up on the flagstone but is easy to wipe away if you make a mistake. Before using the angle grinder to cut the stone, let the diamond wheel run for a minute or so to ensure that the wheel is usable. In some cases, new wheels can be defective, which can lead to damage to the stone or injuries.

Cut the Stone

When you're ready to cut the stone, look for a flat surface to place it on. A garage workbench works well, though you should use a clamp to hold the stone in place. If you don't have workbench, place the flagstone on the grass and use your foot to secure it in place -- just make sure to position your foot away from the cut line. Drop the diamond wheel through the stone, so the weight of the grinder does most of the work. When you're cutting near sharp edges, position the grinder so its wheel spins away from the angle to prevent the stone from going flying or debris from kicking back in your face.