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'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. > > Tony Moss
Consider the cone spalled out by impact from a pellet gun. A spherical pellet - 'BB' caliber in US - will create a smooth cone, apex angle on the order of 90 degrees, though I've never measured it. The angle may be specific to the glass, or it may relate to impact velocity. It would seem that a high speed, light impact would be key. Rather than holding the punch against the glass as you would for metal or wood, possibly "floating" it a few millimeters above the work, so it only touches the glass when struck? Dave -
