As technology related to natural stone has grown over the last 10 years, there have been quantum leaps in the ways to do the simple task of cutting out a sink opening. If you have been fabricating countertops for longer than 10 years, you probably learned (like me) to use a good old 4-in. angle grinder with a 4-in. diamond blade to make a sink opening. On bigger kitchen sinks, you probably learned how to control a worm drive saw and use the rotation of the blade as an asset, not a detriment.
DOING THE WORK BY HAND
Fast forward a decade and there are numerous methods of cutting out sink openings that make the job quicker and easier. Sure, you can rely on the tried-and-true method of hand-cut sink openings, but even that has been improved with the advent of the concave saw blade. I actually can’t remember when I first saw this odd-looking blade that is now available from pretty much every major American tool supply company, but I have to tell you when I first saw one of these blades, I scoffed at the idea and thought it was just some gimmick that was designed to be sold to newbie fabricators who didn’t know any better. Man, was I wrong! I tried using one of these concave blades out of shear curiosity one day, and was shocked at the ease and accuracy of cutting a tight radius! Talk about teaching an old dog a new trick! I now use the concave blade in my training program and strongly advocate its use to anyone that needs a specialty blade to cut a tight radius — especially for sink bowls like the Kohler Caxton Series lavatory sinks. Of course, the concave blade is not designed for straight, long cuts (you can do it if you are REALLY good and have a steady hand), but for a radiused opening the concave blade is now my first choice — IF I am doing the cut by hand.
Another hand-cutting technique that works especially well for larger kitchen sink bowl cutouts is predrilling the inside corners with a diamond core bit. Depending on the size of the inside radius, you have to look at using different bits, but in many cases, the good old 1⅜-in. diamond core that you use for drilling faucet holes will be really handy in helping you perform this technique successfully. I have been using this method for a long time and it helps speed up the overall process. By using the core bit to drill into the inside corners, it eliminates cut marks from when you get too anxious, easing your saw blade into an inside corner. By predrilling a radiused hole at each inside corner, you can cut to the drilled hole and eliminate, or at least reduce, the risk of going too far with your blade. This will help you make sink hole cutouts like a pro!
One last tip that many people don’t think about when cutting a sink opening by hand — or by machine for that matter — is to support the piece that will become the “scrap” you are cutting out while making your cuts. The natural human tendency when cutting any sink opening is to cut out the hole starting at one point of the sink cutout line and going around either in a clockwise or counterclockwise direction, finishing at the point where you started.
Although this is what I consider to be a natural human response based on habit, you have to think differently when cutting a heavy material such as natural or engineered stone, or green (recycled) type slab materials. Think about this: the scrap piece that you will be removing will weigh anywhere from 15 to 40 lbs. depending on the size of the hole you are cutting and the thickness of the stone. If you do not cut and relieve the pressure of flexion evenly around the perimeter of the cutout line, the scrap will create a “lever” effect and potentially crack the good stone that you are trying to fabricate and ship. Some shops (and I am a big advocate of this technique) use a separate support stand for the scrap, so it is supported during the entire cut, thus relieving any flexural pressure on the surrounding stone and making it a safer process.
STEPPING UP THE TECHNOLOGY LADDER
So far I have discussed the hand-made techniques in cutting out a sink opening, but what about the various machines that are available to us as fabricators? Depending on your operating budget, the amount of sink openings that your shop has to turn out in a day and the quality that you are accustomed to delivering, a sink bowl cutout machine may be the answer to your needs (or dreams). There are numerous types of machines that can fill this need, starting with products like radial arm polishers that also are designed to cut a sink opening following a template. There are wire-fed band saws that are not only good for sink bowls, but also are used extensively on the monument side of the industry. And, as we progress farther up the cost scale, there are purpose-built CNC machines that are designed strictly as sink bowl cutout stations, full size CNCs that, hopefully, are not purchased strictly to do sink cutouts and finally waterjet cutting systems.
Remember, any mechanized system will take some time getting integrated into your shop production matrix, but I can tell you firsthand that if I can have a machine do my sink cutouts (and I DO!) I will use it everyday that ends in “Y” and twice on Sundays!
About the author: Kevin M. Padden is owner of AZ School of Rock in Phoenix, Ariz., and KM Padden Consulting. He can be reached at email@example.com or through his Web site at www.azschoolofrock.com.