I recently needed to drill a hole in the top of a 400 day clock glass dome. This is more of a tool review than a repair procedure.

I found these hole saws online that were advertised for glass and ceramic. This set included 5/16" through 1/2" hole saws. I found them on Amazon and there were other manufacturers that had similar diamond coated hole saws. 

I marked the position of the hole with a sharpie. The instructions said to keep the hole saw flooded with water while drilling so I made a dam out of plumbers putty and filled it with water. 

I put some paper towels down on the floor and used my battery drill. The drill only tried to wander for a second or two then it had cut a ridge and held itself in place. 

It took less than a minute to drill all the way through. 

It was a very easy and simple procedure. I would highly recommend purchasing a diamond coated hole saw when the need arises to drill a hole in glass. 

I added a grommet for a nice finished look. 

This full size Schatz had originally had a fitting on the outside of the dome but was missing when I bought the clock. I also made this knob to screw in from the top of the dome. I did most of the shaping with a hand held graver trying to match a similar one I had. The threads were M3X0.5.

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