Rock drill fail

I got some diamond bits to drill through rock.

On my first attempt I decided to go with 30,000rpm and to drill underwater to prevent heat.

The bit fried very quickly.

I need to figure out if it’s a technique thing or if I have the wrong tools.

Perhaps more pressure? Less?

I contacted the ebay seller of the diamond bits. He pointed me to the listing in the link which has this explanation of how to drill which follows below. As it turns out, that’s exactly what I did. Rather annoying that he directed me to the explanation in the listing but it was not in the listing I bought but another. I will try again and if it doesn’t work I’ll not buy from that supplier anymore.


If you are drilling beach glass or any hard or soft stone, you need diamond drill bits. I would suggest this 40 grit 30 piece set to start with. 40 grit will cut very fast and is great for drilling holes. You get an assortment of sizes and shapes which you can experiment with. Eventually you will find certain shapes that work best for your application. I also have a 20 diamond twist drills set for very small holes 1mm and under, but suggest beginners try the larger bits to start with.
The hole you drill will be rough because the 40 grit is coarse and you may want to use a 150 grit drill to smooth the inside of the hole. If you are stringing on wire, you may not need to smooth the inside of the hole but if you string your items on thread, you should follow up with the 150 grit bits.

Start off with good protection. Glass, stone, shell, in powder form is dangerous and not good to breath. Use good eye protection with side protection, get in the habit of using a respirator to protect your nose and mouth against the small particles you will create in the drilling or polishing process. I use a full face shield with a respirator. Also, buy a full size apron and wear it to protect your clothing from dust particles.

I like to drill glass or stone by holding it under water. Put the piece into a shallow container like the lid of an old mayonnaise jar. Be very careful because the combination of water and electricity is dangerous. Hold onto the glass shard (or item to be drilled) with your left hand and hold the flex shaft handle (drill) with a diamond drill bit in your right hand. Insert the drill bit tip (ONLY) through the water and drill the glass shard or stone. (You only need enough water to cover the shard laying on its side). Drill slowly at first and allow the tip to seat and then adjust your drilling once the hole has started. I drill slowly because it allows the tips to last longer. I like to drill half way through the shard and then flip the shard over and drill through the other side of the shard to meet the hole started on the lst side. You will prevent shattering the 2nd side of the hole that way.