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Old 28th May 2017, 11:57 pm   #24
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
Default Re: Any ideas how to mend glass tuner scale?

Ordinary Tungsten Carbide masonry drills work well. I saw their use demonstrated at a do-it-yourself exhibition in the 1950's, where the demonstrator drilled a hole in a bottle by making a ring of putty around the hole's location, filled it with oil, and then used a hand drill, applying heavy pressure and slow speed with the bit immersed in the oil. I have since used the method myself on numerous occasions.

The type of masonry drill used has a tip with a negative rake on its leading edge, and works by crushing the material under the edge of the drill that is in contact with it. This is in contrast to a normal twist drill for metal or wood, where material is removed by the sharp leading edge biting into the surface of the work, getting beneath it, and levering it up.
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