A day of drilling (by alaric)
Last Thursday, I had my safety induction for using the laser cutter at Bristol Hackspace, and as my test piece I laser-cut a name tag for Jean. She likes that sort of thing.
However, she requested that it have a hole in the corner, so she can attach it to her school bag. So today we went down to the workshop and I helped her to drill it out.
But I had more drilling to do. A friend asked me on Facebook how she could drill holes through pebbles. It just so happens that Sarah owns a set of diamond core drills, so I borrowed them and had a go, so that I could offer some advice.
I set the bit up in the column drill:
The challenge was in how to hold the stone still while it was being drilled. Irregular shapes are tricky to hold. First off, I tried a simple clamp:
The drilling has to happen under water, to help cool it and to wash away the dust that the stone turns into. I put some scraps of cardboard underneath so that I drilled into that once I was through the stone, rather than the bottom of my box, which would lead to it leaking all over my cluttered workbench:
As soon as the drill cut in, dust whooshed out into the water and made it impenetrably murky, so after a short drilling session, I took the stone out of the water to see what was happening:
It looked good so I tried again, but this time the stone pivoted in the clamp. I tried to clamp it back again but it wouldn't go back at the same angle and kept shifting, so I tried a new approach - gluing it to a piece of wood that was large enough to not be able to rotate inside the box, so I just needed to hold the box steady while drilling:
That worked quite well, but the vibration shook the stone loose after a while, and I had trouble with the wood wanting to float and the stone wanting to sink causing it to flip over in the water. so I glued it more thoroughly (making sure glue came over the side of the stone so it was held in place rather than just stuck in place), and glued a bit of scrap metal to the bottom to stop it floating over:
That worked; now the stone was steady, it was easy to press on all the way. I had to drill a millimetre then back out (with the drill still spinning) to clear the dust out into the water, then press on again. Progress was slow but steady, taking a few seconds to do each millimetre:
Once I felt it go through the bottom of the stone, I had no trouble in peeling the rubbery hot-melt glue back with my fingernails to free the stone. Job done:
So, to conclude:
- Use a column drill.
- Use a diamond core bit.
- Hold the stone steadily in something that conforms to its shape. An ideal technique might be to use something like Plasticene to firmly secure it to the bottom of the box before pouring the water in.
- Drill slowly, backing off to clean the bit every millimetre or so.
When I came back, Sarah was asleep on the sofa:
Aww!
Alaric, Art and Craft, Jean, Sarah | alaric | 
Sun 13th Jan 2013 8:36 pm
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