Drilling Holes In Gem Stones
Author: Brian Boyle Date Posted:27 April 2015
There is more than one way to drill a hole through a stone but here is a summary of the best way we have found to drill holes in stones:
1. Use a drill press running at slow to moderate speed. Fast speed will wear out the diamond plating on your drill bit.
2. Use a diamond plated (cheap) or sintered (expensive) drill bit. The two main types of plated drill bits are small core drills or Triple Ripple drills from Crystalite.
3. Use plenty of water. Some people prefer to drill underwater using a small container for the water. I prefer to run water to the drilling tip using the thin black micro irrigation tubing used in gardens. You can feed some copper wire into the end of the tubing to make it stiff but still flexible enough to move it to the exact position that you need. Tie the tubing to your drill press with cable ties.
4. A note about safety. You are using a power tool so take all the usual precautions that you would normally do when using water around electricity. Preferably have the drill press on a power circuit that is protected by a safety cut of switch. Use safety glasses too!
5. Don't use the arm of the drill press to lower the bit to the stone - it will exert too much pressure on the drill bit and wear it out faster. You may also break your stone.
6. Mark the stone where you want to drill through ON BOTH SIDES.
7. Hold the stone in both hands and bring it up to the drill bit with the water running. If it is a cabochon the stone may try to slide off the drill bit and cause a scratch. Start your cut at a slight angle until the drill bit starts to bite then straighten up in the direction you want to go.
8. Push the stone firmly but gently against the drill bit using a up and down motion to allow water to constantly reach the drill tip. Running the drill tip dry, even for a short time will quickly wear it out.
9. Drill about half to two thirds of the way through the stone. Depending on the hardness and thickness of the stone this may take between two and five minutes. Do NOT drill right through as this can cause a “blow out” on the back of the stone and you will end up with a crater.
10. Turn the stone over. If you marked the stone on both sides (see number 5) all you have to do is start drilling again until your holes meet up. Lining up the holes gets easier with practice.
11. Keep drilling until you feel the drill bit break through into your original hole.
12. You will now have your hole but it will have fairly sharp edges that may damage the stringing material. To make the hole look better you can chamfer it by using a V or cone shaped diamond burr and gently grind the edge of the holes.
You can also find a video demonstrating this method at: