In ~1988, I attended a lecture at the University of Colorado on the topic of breaking glass. A professor there had studied the subject in depth. I think he was an archeology professor who started by studying how Native Americans made arrowheads (obsidian being very similar to glass). He might have had a grant from the medical industry, because he proposed scalpels made of broken glass for delicate eye surgery. It turns out that broken glass is 100 times sharper than a razor blade.
He had a machine for the precise breaking of glass. I do not know about the shape of the punch therein. I would guess it would be a rounded punch, as a deer antler, since his studies started with arrowheads. I suppose the shock waves that emanate from a point of impact form a cone shape whose apex is the point of impact, hence the break is also cone shaped. Rod Heil 41 N 106 W On Mon, 28 Jul 2003 [EMAIL PROTECTED] wrote: > Andrew James wrote: > > >According to Charles Babbage in his autobiographical "Passages from the > >Life of a Philosopher" (I think, or possibly the "Ninth Bridgwater > >Treatise" - it's many years since I read it) there is a simple technique > >for making a neat hole in a glass sheet using only a centre punch and a > >hammer (gently!). > > SNIP > > >I only tried it once, many years ago, and without success! Practice, and > >probably best of all a demonstration, might help. Has anyone else heard > >of or tried this? > > I'd *guess* that any punch with a plain point would always cause > radiating cracks and shattering of the whole piece BUT a punch that ends > in a hollow cone with a sharp edge might have some success. I must > experiment with a carpenters' nail punch. Alternatively a flat-ended > tool might succeed. > > Some years ago a craftsman showed me how to cut lapped dovetails in wood > with a steel rule which sounds similarly improbable...but it works > beautifully. > > Tony Moss > - > -
