There are several reasons you might want to do this carpentry job: cutting a hole in your countertop. Maybe you are adding an under-sink soap dispenser, or maybe a reverse osmosis system. Whatever the reason, the job doesn’t take a lot of knowledge. You simply need to determine the size of the hole and get busy cutting it.
You will need a drill and a hole saw. A hole saw is a circular tool attached to a drill bit. This allows you to stick it in a drill, which spins it around and cuts the hole. The drill bit sticks out the farthest and this is the first thing to contact the surface to be cut.
Mark the countertop where you want to start the cut. The drill bit will start to drill into the surface. Once it reaches down, the teeth of the hole saw contact the surface. The key here is to hold the drill at a point where all the teeth of the saw are cutting uniformly. If the drill is leaning to one side, only that side of the hole will get cut. This will make the drill wobble. Listen for the sound the saw makes as it cuts. It too should be a uniform sound. If the sound is loud and then soft, the drill is not in a plumb position.
Once you have cut halfway through the countertop, remove the drill and cut the rest of the hole from underneath the counter. The reason is that a lot of hole saws don’t have the depth to cut the entire thing in one shot. In addition you won’t have any tear-out of the surface.