How to Drill a Hole in a Boulder for a Waterfall

Choose a boulder to suit the size of your planned waterfall and complement the rest of the stones. Try out your boulder by pouring water over it from a hose or bucket to see how the water flows. While sandstone or limestone is a lot easier to drill than granite, basalt or other hard stones, softer stones wear away more quickly from flowing water or weather and are more likely to crack or chip than hard-to-drill stones.

Rent a rotary hammer drill with a 1-inch diamond bit. Measure the boulder to determine how long a bit you will need to drill through it. You can drill from both sides and hope to meet in the middlel, but it's messier and chancier than being able to drill straight through the stone.

Dig a shallow depression to cradle a rounded boulder. If the boulder is small enough to fit under a drill press, just position the boulder under the drill bit and clamp it. Larger boulders will have to be professionally drilled in a shop, which is expensive, or manually drilled by you in the backyard. Securing the boulder by partly burying it will help to keep it steady while you work. A flat-bottomed boulder can sit directly on the ground.

Mark the spot for the hole, put on safety equipment, turn on a garden hose with a stopper nozzle and start drilling. Pour water over the drill bit and the deepening hole as you work to reduce friction and cool the drill. The work goes faster if you enlist a friend to help. Provide safety equipment for anyone close to the drill.

Allow the weight and action of the drill to make the hole. Don’t force it. Pull the drill out of the hole after it's an inch deep or so and clear the dust from the hole. Do this repeatedly as you drill through the boulder, recommends the website Rocks4U.

Keep the drill steady and the bit vertical as you work to avoid snapping off the diamond cutters or breaking the bit. When you break through the stone, remove the drill bit, unplug the drill, rinse the hole and file any rough edges. Proceed with building your waterfall.