Art and Decorative Wet Saw Cutting
September 26, 2007
Look at the entry halls of most large hotel or resort projects, and many office buildings, and you will find precision-fit ceramic and natural stone installations inlayed with designs, logos, and artwork produced on a waterjet cutter. Actually, the word cutter is inaccurate since a waterjet works by eroding or grinding very small bits of material with a narrow beam of water accelerated to approximately twice the speed of sound. Modern waterjets were first developed to cut wood, and today, are being used to cut an astonishing array of materials from tissue paper to titanium.
As you might expect, the cost of a multi-processor-controlled tool capable of generating water pressures over 80,000 psi, is going to be out of reach for most tile installers. There are numerous waterjet service companies, and with enough volume, the cost per piece is quite reasonable. Fully computerized systems work fast, with head speeds equal to any diamond blade performing straight cuts, but setup costs are high, making these services unavailable for smaller projects.
Safety First!Opportunities for inlay work normally do not come with every job, but when they do, it is good to know that some elaborate, curved cutting can be done on the wet saw you already own. Before getting into the how-tos, it is a good idea to review the safety aspects of using a wet saw. First, the motor should be grounded and in good condition with air vents, if any, clean and not blocked by spray dust. The blade should be flat, with no cracks or missing sections of diamond rim, the coolant pump should be robust, and the catch pan filled with cool, clean water. Safety lenses are a must, and hearing protection is always advised when using the wet saw. Regarding blades, I do a lot of straight and curved cutting on both soft and hard materials, and find that keeping several different blades on hand is more economical than relying on a single, multi-purpose blade. When purchasing a blade, the first thing I do is record the diamond rim’s thickness and depth in the tool log, and use the blade for straight cutting until 60 percent of the rim has been worn away. At that point, I confine the blade to curve-cutting only. The reason? Curve-cutting generally wears one side of the cutting rim more than the other; consequently, once a blade has been used for cutting curves, it is incapable of cutting straight, and can be a safety hazard if used this way. Curve-cutting a few tiles should not pose any dangers; I am referring here to a blade that is primarily used to cut curves freehand.
The other main safety issue concerns how curve cutting is done: the tile is held in your hands rather than sitting flat and firm against the saw table. If the blade gets pinched in the kerf, the tile can be violently yanked from your grip hand, or worse, parts of the cutting rim can break off. Rest the heels of your hands on the saw table for stability, ensure that the blade is never pinched, and always remain focused on the task. I learned this method 38 years ago, have never been hurt or injured by the practice, and have created many beautiful installations with the technique, by using common sense, and by working patiently.
Marking tiles for cuttingMarking a tile can be a problem because the coolant water tends to erode cutting lines made with a pencil or even a Sharpie™. To prevent this, cover the cut area with a smooth application of masking tape, and mark the tape with a ballpoint pen or sharpened pencil. Keep the tape dry until cutting: the tape I use, a 3M brand, remains laminated for about 2 minutes before it begins to pucker, bulge, or pull away from the tile. To balance its limited resistance to water, masking tape leaves behind no adhesive residue that could mar the surface of the tiles, or require cleaning. For the greatest accuracy, the ideal width of the cut lines should be consistent and no wider than the mark of an average ballpoint pen. The mark should be centered over the edge of the cut so that after cutting, half the line still remains – a positive indication that the cut was made correctly. This is especially useful as a production and QC tool, and indispensable when somebody else is doing the cutting: the tape left on the cut tile serves as “evidence” in case the piece does not fit, and determines whether I measured wrong, or my helper did not follow the mark.
Freehand cuttingThe process of cutting freehand curves begins with a series of straight cuts whose purpose is to remove as much unwanted material with the fewest possible cuts. To make the process of freehand cutting more comfortable, you may want to raise the wheel and inch or two. Initial cuts all end in a “V”, so that one kerf intersects with another. Secondary cuts are also V-shaped, depending on the position of the cut lines, and angles available to the blade. When cutting, hold the tile firmly on each side of the cut, and aim the body of the tile towards the blade’s hub for a square-shouldered blind cut: A square-shouldered cut is the main reason for holding the tile off the table. When segment-roughing the tile, always cut straight, and as close to the cut lines as possible to reduce the amount of side-cutting required. Side-cutting is the third phase of freehand cutting.
Once the negative area has been roughed out with straight cuts, use the side of the diamond rim to gradually grind away excess material. To maintain control, plant the heel of each hand firmly against the cutting table, maneuver the tile with your thumb and fingers, and move the tile from side to side to keep the kerf wide enough so that it does not grab the blade during this part of the process. With experience, you should be able to easily cut to the center of the line. The trick is to remove material gradually. The first and second round of cutting is for hogging off material in bulk, but in round three, the work has to be done gently: with a 40% rim, no more than 1/32-inch should be removed in a single pass.
Depending on the amount of material remaining to be removed, multiple passes will be required to finish some areas, while other parts may need only a light dusting with the rim. Either way, strive to leave half of the cut line visible on the masking tape. Because of the angle of exposure to the blade, outside curves are easier to complete than inside. After the tiles are cut, and depending on the material, the cut edge should be smoothed over or beveled with the diamond blade to mimic the factory edge.
Drilling and coring tileA common practice among many tile installers, when a hole through a tile is needed for a plumbing penetration, is to split the tile and nibble out two half-moons with a pair of biters. Split tiles are a sign of amateur-quality work, and are not permitted according to ANSI A108.02, 4.3.5. Instead of splitting the tile, use a core bit. I prefer diamond core bits over carbide, and always use water to cool the bit and tile, and to vastly extend the life of the tool. Core bits can be used with pilot drills, but carbide bits won’t go through porcelain tiles, so I prefer to use either a wooden guide placed over the tile, or even better, a drill press with a water bath. To do this, I use a shallow wood box to contain the water, keep a minimum 1/2-inch of water above the tile at all times, and lift the core bit frequently so water has a chance to flush out the debris.
Using a ring sawI use a regular tile wet saw to perform a variety of cutting tasks, but there are limits to what can be done with a solid blade. For this reason, when the cutting gets really complicated, or when the path of the cut is too tight to allow access to a solid blade, I use another type of wet saw called a ring saw. Ring saws are not designed to match the performance and stamina of a regular wet saw and diamond blade, but a ring saw can cut on a forward, backward, or side stroke, and follow any cut line. A regular ring saw can cut at any angle, and a special blade is available with a coupling that allows the blade to be taken apart, and slipped through a drilled hole for blind cutting.
If you are going to be in the business of installing tile, aiming for custom work is a better business plan than trying to be the cheapest installer in town. Through the creative use of the wet saw you are already familiar with, plus the addition of a few core bits and a ring saw, you will not have to spend $250K on a waterjet.