drill old gass
On Sun, 13 Mar 2011 12:48:39 +0000, David Billington
wrote:
Karl Townsend wrote:
Milady needs me for my shop skills. Don't happen that often.
She has old canning jars. The type with a glass lid and a little wire
arrangement to pull the glass lid tight. She wants to put small lights
inside and needs a hole drilled. I haven't measured up for sure, but
I'm thinking this stuff is 1/8 NPT size.
OK, how do I drill very old glass? I get several points off for every
one I break.
Karl
The old way would be to use some copper or brass tube with an OD the
size of the hole you want. Make a dam round the hole with plasticene and
add some abrasive like valve grinding paste and a bit of water or oil,
Hold the tube in a drill press running at a slow speed and repeatadly
apply pressure and lift. The abrasive imbeds in the softer tube material
like a lap and grinds through the glass.
The new way would be to use a diamond hole saw but still have the dam to
retain water to keep the glass cool. You can probably buy them on eBay
for a few dollars in the size you want.
I used a cordless screwdriver powering a copper or brass tube through
a 1/4" square drive U joint and very little pressure.
Gerry :-)}
London, Canada
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