Overview: You need two key tools
Dry-cut diamond blade
A diamond blade has diamond grit embedded in the steel rim to grind away hard materials.
Stone, porcelain and glass tiles offer beautiful options for bath and kitchen tiling projects. But cutting these hard materials presents a unique challenge. Straight cuts are easy to make with a diamond wet saw. But cutting curves and holes requires special techniques.
In this article, we’ll show you how to use an inexpensive angle grinder with a diamond blade to cut perfect circles and squares in even the toughest tile. You can buy a 4-in. or 4-1/2-in. grinder for as little as $50 and a dry-cut diamond blade to fit it starting at $20. In general, more expensive blades will last longer. When you’re choosing a diamond blade, look for one with a continuous, rather than segmented rim for the smoothest cut.
Be aware, though, that cutting with a dry-cut diamond blade creates a lot of dust and noise. So make sure you cut in a well-ventilated area (or better yet, outside!) and wear hearing protection, a good-quality two-strap dust mask and safety glasses.
Tilt the blade for cutting circles
Photo 1: Score the circle
Score the front of the tile along the circle guideline with the diamond blade. Tilt the grinder about 30 degrees and cut about 1/16 in. deep.
Photo 2: Make angle cuts
Move the blade 1/8 in. to the inside of the line and make a deeper cut. Continue moving the blade away from the line and cutting deeper until you cut completely through.
Photo 3: Smooth the cut edge
Grind off rough edges and trim back to the line for a perfect curve.
Many tile jobs require you to cut one or more large round holes for floor drains or shower valves. Photos 1 – 3 show how to cut a hole for a shower valve. We’re showing how to cut a hole that’s entirely within a single tile, one of the most difficult cuts. In the next section we’ll show you an easier method to use for cutting curves in the edge of a tile.
Even with this method, try to avoid a tile layout that places the edge of the circular cutout less than 1/2 in. from the edge of a tile. It’s better to shift the entire layout instead. Otherwise, chances are good that you’ll break the tile at the narrow point while cutting.
The method shown for cutting a circle with a grinder and diamond blade requires you to cut around the circle a number of times, making a deeper cut with each revolution. The key is to maintain the same angle and shave off progressive layers, moving the cut closer to the center of the circle (Photo 2).
Make accurate, near perfect circle cuts for shower valves and plumbing pipes with this technique.
Rough out semicircular cuts before trimming to the line
Photo 1: Score and rough cut
Score the profile with the saw, then cut in from the edge of the tile to remove as much waste as possible.
Photo 2: Trim and grind
Make a series of closely spaced cuts up to the scored line. Break off the waste. Then grind the edges smooth.
The process for cutting semicircles from the edge of tiles is similar to the technique shown for full circles. You start by marking the cut and scoring the face of the tile on the line. Then, rather than deepen the scoring cut, simply remove the excess tile with straight cuts (Photo 1).
Before you remove the excess tile (Photo 1), be sure to make short cuts on both sides of the semicircle (1 and 2). Then connect the cuts as shown (3). Rather than make this connecting cut in one pass, make a series of progressively deeper shallow cuts until you’re through the tile.
Now complete the semicircle with a series of radial cuts—like the spokes of a wheel (Photo 2). Finish by cleaning up the rough edges with the diamond blade. Or remove the “tabs” with a tile nipper (a pliers-like biting tool). Then grind the edges smooth.
Smooth Semicircular Cuts
Take a two step approach to cutting smooth semicircular shapes.
Make a dish-shaped cutout for small holes
Photo 1: Plunge cut
Center the cut on the hole and plunge slowly from the back. Stop when the slot through the face of the tile lines up with the edges of the desired cutout.
Photo 2: Repeat plunge cut
Draw another larger circle to guide the depth of the remaining cuts. Make repeated plunge cuts until the circle is complete.
Most plumbing pipe holes are covered by a decorative escutcheon or hidden by a fixture base, so a precise round hole isn’t necessary. Use the technique shown here to make rough, round holes.
Start by marking the circular cutout on the back of the tile. Then plunge the diamond blade down through the tile, keeping it centered on the hole so that the slot made by the blade extends equally on both sides of the circle marks (Photo 1). Check often to see when the slot through the front of the tile reaches the edges of the desired cutout. Then use the length of that plunge cut to gauge the diameter of a second, larger circle. Draw that larger circle on the back of the tile (Photo 2). Use this circle as a guide for making the rest of the plunge cuts. Rotate the grinder about a blade’s width and make another plunge cut, stopping at the outer circle. Continue this process until you finish the hole.
Small Hole Technique
Cut small holes from the backside with plunge cuts.
Plunge-cut from the back to make rectangular cutouts
Photo 1: Score the front
Mark the cutout on the front and back of the tile precisely. Then score the front of the tile about 1/16 in. deep along the line.
Photo 2: Plunge cut the back
Flip the tile over and plunge the cut from the back. Stop and check often. Stop when the cut lines up with the corners of the marked square on the front. Plunge-cut the remaining three sides.
Cutting rectangular or square holes for electrical outlets is simple with this method. The key is to avoid cutting beyond the corners of the square where the cut might be visible. Plunge-cut slowly from the back and check often to avoid going too far.
Make rectangular cutouts with plunge cuts from the back side.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Angle grinder
- Dust mask
- Hearing protection
- Safety glasses