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How to Drill Through River Stone

Julie Keyes

River rocks are a popular stone for many kinds of projects because of their smooth roundness and appealing colors. These stones were at one time much larger but over thousands of years of working downstream from mountains through the water, were worn smooth by the force of the water and sediments rushing over them. River stone comes in small marble size on up to basketball size. Some stones will resist drilling, so discard these in favor of softer stones.

River stone is rounded by thousands of years of abrasive contact with water and sediment.
  1. Select stones to drill. Base your choices on color, texture and personal preference. Keep in mind that it is easier to drill a flatter stone than a rounded one.

  2. Place rubber or leather scrap pieces on either side of a stone and tighten it securely in a vise. The rubber or leather protects the side from marring in the vise and helps to hold it in place without slipping. Ensure that the side you wish to drill is facing up.

  3. Choose the diameter of hole to drill. The drill bit size should not exceed more than twice the distance from the center to outer edge or the stone may break. Locate the approximate center position on the stone and place a dot with a magic marker to see it easily.

  4. Roll a length of plumbers putty into a 1/2-inch diameter strand. Position it on the stone and make a ring around the dot with a marker. Pinch the ends of the putty together to seal the circle and press it down onto the stone to get a good seal. Depending on the size of the stone, make the ring large enough to hold 1/4-inch of water while drilling.

  5. Fill the putty ring with water, place a diamond-tipped drill bit of the size desired in a heavy-duty power drill and secure it tightly. Position the tip of the drill bit straight down against the marker dot. Hold the drill securely with both hands to steady it and slowly start the speed. Increase the speed gradually to ensure a clean cut and to protect the bit.

  6. Stop periodically and check the stone for progress and the bit for damage. If the stone isn't cutting well, consider choosing a new one that is more receptive to drilling. Add water to the putty ring as it burns away to help lubricate and keep the bit cool.

  7. Remove the putty as soon as the stone is drilled through. Set the stone aside and move on to the next one.